Explore Decorator Design Pattern In Dart

Design

-

April 23, 2025

One of the well-known design patterns, the Decorator one, explains how to design flexible and reusable object-oriented software by resolving common design issues. We’ll cover the decorator design pattern, a structural design pattern often referred to as a wrapper.

This blog will Explore Decorator Design Pattern In Dart. We see how to execute a demo program in your applications.

If you’re looking for the best Flutter app development company for your mobile application then feel free to contact us at — support@flutterdevs.com.

Table Of Contents::

What is the Decorator Design Pattern?

What is the Decorator Design Pattern?:

“Design Patterns, Elements of Reusable Object-Oriented Software,” a book, dynamically assigns additional responsibilities to an object. When it comes to expanding functionality, decorators offer a flexible alternative to subclassing.

Let’s try to understand this with a real-world example that might make more sense: suppose you order a plain coffee from a coffee shop. Here, coffee acts as a class object. You want to spice up your coffee now. You request that some milk be added. The barista pours some milk into your coffee. Here, the milk enhances your coffee without altering it in any way.

You decide later that you also want some sugar. Sugar is added to your coffee by the barista. Another decorator is sugar. It enhances your coffee even more without altering the milk or coffee.

In this scenario, your coffee is the object, and milk and sugar are the decorators. To put it more succinctly, the Decorator design pattern does not alter the structure of objects but rather adds new functionality to them.

When to use?:

When would you like to add new responsibilities to an object transparently and dynamically?
Because there are too many separate extensions, subclassing is not a realistic way to increase functionality.
When would you like to assign tasks to objects in layers or phases?
When you need to add optional functionality but yet want to keep a class focused on a particular task.

Code Implement:

A basic coffee is called plain coffee. Asking the barista to add more milk or sugar is what ExtraMilkDecorator and ExtraSugarDecorator do. Without changing the original PlainCoffee, they can modify the coffee’s price and description.

abstract class Coffee {
  String get description;
  double get cost;
}

class PlainCoffee implements Coffee {
  @override
  String get description => 'Plain Coffee';

  @override
  double get cost => 60.0;
}

class CoffeeDecorator implements Coffee {
  final Coffee coffee;
  CoffeeDecorator(this.coffee);

  @override
  String get description => coffee.description;

  @override
  double get cost => coffee.cost;
}

class ExtraMilkDecorator extends CoffeeDecorator {
  ExtraMilkDecorator(super.coffee);

  @override
  String get description => '${coffee.description} + Extra Milk';

  @override
  double get cost => coffee.cost + 15.0;
}

class ExtraSugarDecorator extends CoffeeDecorator {
  ExtraSugarDecorator(super.coffee);

  @override
  String get description => '${coffee.description} + Extra Sugar';

  @override
  double get cost => coffee.cost + 20.0;
}

void main() {
  Coffee coffee = PlainCoffee();
  print("${coffee.description}: \$${coffee.cost}");

  coffee = ExtraMilkDecorator(coffee);
  print("${coffee.description}: \$${coffee.cost}");

  coffee = ExtraSugarDecorator(coffee);
  print("${coffee.description}: \$${coffee.cost}");
}

When we run the application, we ought to get the screen’s output like the underneath console output.

Plain Coffee: $60.0
Plain Coffee + Extra Milk: $75.0
Plain Coffee + Extra Milk + Extra Sugar: $95.0

Process finished with exit code 0

Drawbacks:

A complicated codebase that is difficult to maintain can result from overusing the Decorator pattern.
A more complex class hierarchy is produced by creating multiple minor classes for every new functionality.
It necessitates numerous small classes, all of which are fairly similar to one another, potentially making the design unduly complex.

Conclusion:

In the article, I have explained the Decorator Design Pattern basic structure in a dart; you can modify this code according to your choice. This was a small introduction to the Decorator Design Pattern On User Interaction from my side, and it’s working using Dart.

I hope this blog will provide you with sufficient information on trying the Explore Decorator Design Pattern In Dart in your projects. One of the most widely used design patterns for dynamically adding additional functionality to an object without altering its structure is the Decorator pattern.

It provides a versatile substitute for subclassing, especially when handling numerous independent extensions.ut it’s crucial to utilise this approach sparingly because excessive use might result in a complicated and challenging-to-maintain codebase. Despite these difficulties, the Decorator design can greatly improve your code’s readability and modularity when applied properly. So please try it.

❤ ❤ Thanks for reading this article ❤❤

If I got something wrong? Let me know in the comments. I would love to improve.

Clap 👏 If this article helps you.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutter developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

Implement Folding Scroll In Flutter

Packages and Plugins

Shaiq Khan

-

April 18, 2025

0

Flutter, almost everything is a widget — even format models are widgets. The photos, symbols, and text in a Flutter application are on the widgets. Anyway, things you don’t see are extra widgets, similar to the rows, columns, and grids that arrange, oblige and align the conspicuous widgets.

In this blog, we will explore implementing a Folding Scroll In Flutter. We will see how to implement a demo program of the folding scroll and create a folding (horizontal) scroll of a list view using PageView.builder in your Flutter applications.

If you’re looking for the best Flutter app development company for your mobile application then feel free to contact us at — support@flutterdevs.com.

The above demo video shows how to implement Folding Scroll in a flutter. It shows how the Folding Scroll will work using the PageView.builder in your flutter applications. It shows when the user swipe left to right then, images will scroll and overlap with other images. It will be shown on your device.

Constructor:

To utilize PageView.builder, you need to call the constructor underneath:

PageView.builder({
  Key? key,
  this.scrollDirection = Axis.horizontal,
  this.reverse = false,
  PageController? controller,
  this.physics,
  this.pageSnapping = true,
  this.onPageChanged,
  required IndexedWidgetBuilder itemBuilder,
  ChildIndexGetter? findChildIndexCallback,
  int? itemCount,
  this.dragStartBehavior = DragStartBehavior.start,
  this.allowImplicitScrolling = false,
  this.restorationId,
  this.clipBehavior = Clip.hardEdge,
  this.scrollBehavior,
  this.padEnds = true,
})

All fields marked with @required must not be empty in the above Constructor.

Properties:

There are some properties of PageView.builder are:

> itemBuilder: This property is called only with indices greater than or equal to zero and less than itemcount.
> restorationId: This property is used to take in a string as the object. It is used to save the scroll position and later restore it.
> clipBehavior: This property is used to the content will be clipped (or not) according to this option.
> padEnds: This property is used to add padding to both ends of the list.
> scrollDirection: This property is used to the axis along which the page view scrolls. Defaults to [Axis.horizontal].
> onPageChanged: This property is used to call whenever the page in the center of the viewport changes.

Implementation:

Step 1: Add the assets

Add assets to pubspec — yaml file.

assets:
  - assets/

Step 2: Run flutter packages get in the root directory of your app.

How to implement code in dart file :

You need to implement it in your code respectively:

Create a new dart file called dummy_data_model.dart inside the lib folder.

In this dart file, we will create a dummyDataModel. Inside we will add the array of the item.

var dummyDataModel = [
  "assets/demo_1.png",
  "assets/img.png",
  "assets/logo.png",
  "assets/demo_2.png",
  "assets/powered_by.png",
  "assets/demo_3.png",
  "assets/demo_4.png",
];

Create a new dart file called page_view_item.dart inside the lib folder.

In this dart file, we will create PageViewItem class. In this class, we will add int index, string image, and double width. In the build method, we will return Inkwell. Inside, we will add onTap and its child we will add a Card widget. In this widget, we will add elevation, shape, and Image. asset().

import 'package:flutter/material.dart';

class PageViewItem extends StatelessWidget {
  final int index;
  final String img;
  final double width;

  const PageViewItem({
    Key? key,
    required this.index,
    required this.width,
    required this.img,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: () => print(index),
      child: Card(
        elevation: 8,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(1.0),
        ),
        child: Image.asset(
          img,
          fit: BoxFit.fill,
          width: width,
        ),
      ),
    );
  }
}

Create a new dart file called home_page.dart inside the lib folder.

First, we will create a double variable _page equal to zero, and the index of the left-most element of it to be displayed.

double _page = 0;
int get _firstItemIndex => _page.toInt();

Presently, we configure our page view and make the PageController where we give the viewportFraction. It characterizes the negligible portion of the viewport that each page ought to possess. Defaults to 1.0, implying each page fills the viewport in the looking over heading.

final _controller = PageController(
  viewportFraction: 0.5,
);

Now, we will calculate the width of the single items on the pageview.

late final _itemWidth =
  MediaQuery.of(context).size.width * _controller.viewportFraction;

Then, we will create an initState() method. In this method, we will add the controller inside the initState.

@override
void initState() {
  super.initState();
  _controller.addListener(() => setState(() {
        _page = _controller.page!;
      }));
}

In the body, we will add a Column widget with crossAxisAlignment and mainAxisAlignment as the center. Inside, the widget we will add the Stack widget.

Column(
  crossAxisAlignment: CrossAxisAlignment.center,
  mainAxisAlignment: MainAxisAlignment.center,
  children: [
    const SizedBox(height: 10,),
    Stack(
      children: [
        Positioned.fill(
          child: Align(
            alignment: Alignment.centerLeft,
            child: SizedBox(
              height: 200,
              width: _itemWidth,
              child: FractionallySizedBox(
                child: PageViewItem(
                  index: _firstItemIndex,
                  width: _itemWidth,
                  img: dummyDataModel[_firstItemIndex],
                ),
              ),
            ),
          ),
        ),
        SizedBox(
          height: 200,
          child: PageView.builder(
            padEnds: false,
            controller: _controller,
            itemBuilder: (context, index) {
              return Opacity(
                opacity: index <= _firstItemIndex ? 0 : 1,
                child: PageViewItem(
                  index: index,
                  width: _itemWidth,
                  img: dummyDataModel[index],
                ),
              );
            },
            itemCount: dummyDataModel.length,
          ),
        ),
      ],
    ),
  ],
),

In this Stack widget, we will add FractionallySizedBox. Inside, we will add PageViewItem class. In this class, we will add index, width, and img. Then, we will add SizedBox with height. Its child, we will add PageView.builder. Inside, we will add padEnds, controller, itemBuilder and itemCount.

When we run the application, we ought to get the screen’s output like the underneath screen capture.

Code File:

import 'package:flutter/material.dart';

import 'dummy_data_model.dart';
import 'page_view_item.dart';

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  double _page = 0;

  int get _firstItemIndex => _page.toInt();

  final _controller = PageController(Hire flutter developer
    viewportFraction: 0.5,
  );

  late final _itemWidth =
      MediaQuery.of(context).size.width * _controller.viewportFraction;

  @override
  void initState() {
    super.initState();
    _controller.addListener(() => setState(() {
          _page = _controller.page!;
        }));
  }

  @override
  void dispose() {
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.grey[200],
      appBar: AppBar(
        automaticallyImplyLeading: false,
        title: const Text("Flutter Folding Scroll Demo"),
        backgroundColor: Colors.cyan,
        centerTitle: true,
      ),
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.center,
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          const SizedBox(
            height: 10,
          ),
          Stack(
            children: [
              Positioned.fill(
                child: Align(
                  alignment: Alignment.centerLeft,
                  child: SizedBox(
                    height: 200,
                    width: _itemWidth,
                    child: FractionallySizedBox(
                      child: PageViewItem(
                        index: _firstItemIndex,
                        width: _itemWidth,
                        img: dummyDataModel[_firstItemIndex],
                      ),
                    ),
                  ),
                ),
              ),
              SizedBox(
                height: 200,
                child: PageView.builder(
                  padEnds: false,
                  controller: _controller,
                  itemBuilder: (context, index) {
                    return Opacity(
                      opacity: index <= _firstItemIndex ? 0 : 1,
                      child: PageViewItem(
                        index: index,
                        width: _itemWidth,
                        img: dummyDataModel[index],
                      ),
                    );
                  },
                  itemCount: dummyDataModel.length,
                ),
              ),
            ],
          ),
        ],
      ),
    );
  }
}

Conclusion:

In the article, I have explained the basic structure of Folding Scroll in a flutter; you can modify this code according to your choice. This was a small introduction to Folding Scroll On User Interaction from my side, and it’s working using Flutter.

I hope this blog will provide you with sufficient information on trying up the Folding Scroll in your Flutter projects. We will show you what an Introduction is?. Show the properties and constructor of Folding Scroll. Make a demo program for working in your Flutter applications. So please try it.

❤ ❤ Thanks for reading this article ❤❤

If I got something wrong? Let me know in the comments. I would love to improve.

Clap 👏 If this article helps you.

GitHub Link:

find the source code of the Flutter Folding Scroll Demo:

GitHub – flutter-devs/flutter_folding_scroll_demo
A new Flutter project. This project is a starting point for a Flutter application. A few resources to get you started…github.com

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire flutter developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Related: SMS Using Twilio In Flutter

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

Stripe Subscriptions in Flutter

Featured

Ritutosh Bhatia

-

April 17, 2025

0

Introduction

Subscription-based monetization models have gained significant traction in the mobile app industry, enabling businesses to establish a sustainable revenue stream while offering premium content, exclusive features, or ongoing services to users. Instead of relying on one-time purchases, subscriptions allow developers to maintain a steady income while providing users a seamless experience.

Stripe is one of the most powerful and developer-friendly payment gateways available. It is known for its robust security features, seamless integration capabilities, and support for various payment methods. Businesses widely use it for recurring billing and subscription management.

In this guide, we will walk through the step-by-step process of implementing Stripe subscriptions in a Flutter application. The tutorial will cover:

Setting up a Stripe account and configuring subscription products
Integrating Stripe’s payment gateway in a Flutter app
Implementing a backend service for handling subscriptions
Managing subscription cancellations, upgrades, and downgrades
Following best practices for efficient subscription-based monetization
Comparing Stripe with alternative payment solutions
Identifying limitations and exploring the future scope of subscription payments

By the end of this guide, you will have a fully functional subscription model integrated into your Flutter application.

If you’re looking for the best Flutter app development company for your mobile application then feel free to contact us at — support@flutterdevs.com.

const express = require("express");
const stripe = require("stripe")("your_secret_key");

const app = express();
app.use(express.json());

app.post("/create-subscription", async (req, res) => {
  try {
    const customer = await stripe.customers.create({
      email: req.body.email,
    });

    const subscription = await stripe.subscriptions.create({
      customer: customer.id,
      items: [{ price: "price_id_from_stripe_dashboard" }],
      expand: ["latest_invoice.payment_intent"],
    });

    res.json({ subscriptionId: subscription.id });
  } catch (error) {
    res.status(500).send(error.message);
  }
});

app.listen(3000, () => console.log("Server running on port 3000"));

Step 2.4: Handling Subscription Payment in Flutter

Once the backend API is in place, call it from the Flutter app to initiate a subscription.

import 'package:flutter_stripe/flutter_stripe.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

Future<void> createSubscription(String email) async {
  try {
    final response = await http.post(
      Uri.parse("https://your-backend.com/create-subscription"),
      body: jsonEncode({"email": email}),
      headers: {"Content-Type": "application/json"},
    );

    final data = jsonDecode(response.body);
    print("Subscription successfully created: ${data["subscriptionId"]}");
  } catch (error) {
    print("Error creating subscription: $error");
  }
}

Step 2.5: Managing Subscriptions (Cancellation & Modifications)

To enhance the user experience, we should allow users to cancel, upgrade, or downgrade their subscriptions.

Cancel a Subscription (Backend — Node.js)

app.post("/cancel-subscription", async (req, res) => {
  try {
    await stripe.subscriptions.update(req.body.subscriptionId, {
      cancel_at_period_end: true,
    });
    res.json({ message: "Subscription cancellation scheduled" });
  } catch (error) {
    res.status(500).send(error.message);
  }
});

Flutter Function to Cancel a Subscription

Future<void> cancelSubscription(String subscriptionId) async {
  try {
    final response = await http.post(
      Uri.parse("https://your-backend.com/cancel-subscription"),
      body: jsonEncode({"subscriptionId": subscriptionId}),
      headers: {"Content-Type": "application/json"},
    );

    final data = jsonDecode(response.body);
    print(data["message"]);
  } catch (error) {
    print("Error canceling subscription: $error");
  }
}

3. Limitations of Stripe Subscriptions

Backend Dependency: Stripe subscriptions require a backend for creating customers, handling payment events, and managing renewals.
Compliance Requirements: Applications using Stripe must adhere to PCI-DSS security standards and SCA authentication for payments.
Regional Restrictions: Stripe is not available in some countries, limiting its global accessibility.
Webhook Management: Developers must implement webhook listeners to handle real-time updates regarding subscription status.

4. Best Practices for Subscription Implementation

Use Test Mode Before Deployment: Stripe provides test keys to simulate transactions before going live.
Handle Payment Failures Gracefully: Implement retry mechanisms and notify users when payments fail.
Monitor Webhooks for Real-Time Updates: Webhooks help in tracking subscription renewals, cancellations, and failures.
Allow Easy Cancellations to Maintain Trust: Users should be able to cancel their subscription without friction.
Secure API Keys and Payment Data: Never expose Stripe’s secret key in the frontend. Use backend authentication for handling payments.

5. Future Scope of Subscription Payments

Artificial Intelligence in Pricing Models: AI-driven pricing strategies can personalize subscription plans based on user behavior.
Blockchain-Based Payments: Cryptocurrency transactions for subscriptions could enhance transparency and reduce processing fees.
Serverless Payment Handling: Payment systems may shift towards fully serverless architectures, simplifying implementation.
Cross-App Subscription Bundling: Users may be able to purchase a single subscription covering multiple services across different applications.

6. Conclusion

Stripe simplifies subscription-based payments in Flutter, providing a secure and efficient solution. With its global reach, automated billing management, and developer-friendly APIs, it remains a top choice for subscription-based applications. Following best practices and optimizing ad placements can ensure higher conversion rates and long-term customer retention.

7. Reference

flutter_stripe | Flutter package
Flutter library for Stripe. Supports PaymentSheets, Apple & Google Pay, SCA, PSD2 and much more.pub.dev

Flutter Stripe
Flutter library for Stripe.docs.page

❤ ❤ Thanks for reading this article ❤❤

If I got something wrong? Let me know in the comments. I would love to improve.

Clap 👏 If this article helps you.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutter developer for your cross-platform Flutter mobile app project hourly or full-time as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

Implementing State Management in FlutterFlow

Statemanagement

Umesh Raghav

-

April 11, 2025

0

State management is a crucial part of any Flutter or FlutterFlow application. It refers to how you manage and maintain the state of your UI components — essentially how your app responds to user interactions, backend updates, and internal logic changes. In FlutterFlow, managing state becomes easier thanks to its built-in tools and visual interface.

Let’s walk through the essentials of state management in FlutterFlow, the available tools, and how you can implement it effectively in your project.

What is State in FlutterFlow?

In simple terms, state is any data that can change in your app — like user input, page navigation, visibility of a widget, toggle switches, or fetched data from APIs or Firebase. FlutterFlow offers multiple ways to handle and update this data without having to write complex Flutter code manually.

🛠Types of State Management in FlutterFlow

1. Local State (UI State)

Local State is used to manage state within a specific page or widget. For example, toggling a switch or showing/hiding a container based on a boolean value.

Ideal for: temporary state, like modal visibility or tab selection.
Managed directly using FlutterFlow’s Variables panel under Page State.

Example:

You can create a local boolean variable like isVisible to control whether a widget is shown or hidden.
Update this variable on button tap, and the UI will rebuild accordingly.

2. App State (Global State)

App State is used to manage global variables that need to persist and be shared across different pages/screens.

Ideal for: user authentication info, selected language, user preferences.
Accessible anywhere in your app.

Example:

When a user logs in, store their username and userID in App State. These can then be used on different screens like profile, dashboard, or order history.

3. Firebase-Connected State

If you’re using Firebase, FlutterFlow offers powerful tools to bind your UI elements directly to Firebase collections and documents.

Ideal for: displaying live data such as user profiles, product listings, orders, etc.
Automatically updates when the backend changes (real-time sync with Firebase).

Example:

Display a list of products from a Firestore collection using a ListView connected to a Firebase query.

4. Custom Functions (Advanced State Updates)

If you need more control, you can define custom functions in Dart within FlutterFlow. These functions can modify state, perform calculations, or run conditional logic.

Ideal for: complex state changes, API data manipulation, calculations.
⚙️ Use them inside Actions → Run Custom Function.

5. Bloc Pattern (For Advanced Flutter Developers)

While FlutterFlow simplifies state management, advanced users may integrate Bloc/Cubit using the Custom Code section. This is ideal for teams who want fine-grained control and clean architecture.

How to Use State Variables in FlutterFlow Step-by-Step:

1. Create a State Variable

Go to the Variables panel.
Choose Local, App, or Component State.
Name your variable and assign an initial value.

2. Update the State

Use the Action Editor to modify state (e.g., on button press → Update Variable).

3. Bind State to Widgets

Use the variable in visibility conditions, text values, or widget properties.

4. Observe State Changes

FlutterFlow will automatically update the UI when the state changes.

Real-Life Use Cases

Toggle between light/dark mode using a state variable.
Update cart items in an e-commerce app using local state variables.
Store user login info in App State for persistent access.
Fetch and display user profile details from Firebase using state-driven widgets.

Best Practices

Use Local State for page-specific or temporary UI behavior.
Use App State for global data you need across the app.
Keep Firebase collections optimized for fast querying and updates.
Group state logically and use meaningful names for clarity.

Conclusion

State management may seem complex at first, but FlutterFlow simplifies the process with a visual and intuitive approach. Whether you’re creating a basic form or a dynamic, real-time dashboard, managing state correctly is key to building responsive and efficient apps.

By leveraging FlutterFlow’s built-in state tools, you can develop scalable and user-friendly applications—without diving deep into boilerplate code. And for more advanced needs, FlutterFlow offers the flexibility to integrate custom Dart logic, giving you the best of both no-code and low-code development.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutterflow developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

Dismissible In Flutter

Widgets

Shaiq Khan

-

April 9, 2025

0

In Flutter, assuming you want to make a widget that can be dismissed, you can wrap the widget as the child of Dismissible. A dismissible Widget in Flutter is typically used to wrap each list item with the goal that it tends to be excused, either horizontally or vertically direction.

This blog will explore the Dismissible In Flutter. We perceive how to execute a demo program. We will figure out how to utilize the widget, including how to show the confirmation dialog, set backgrounds that will be shown when the child is being dismissed, and set dismissed directions in your Flutter applications.

If you’re looking for the best Flutter app development company for your mobile application then feel free to contact us at — support@flutterdevs.com.

Table Of Contents::

Introduction:

A widget can be dismissed by dragging in the demonstrated direction. Dragging or hurling this widget in the DismissDirection makes the child slide out of view.

Demo Module ::

This demo video shows how to use the dismissible in a flutter and shows how a dismissible will work in your flutter applications. We will show a user dragging or fingering by dismissing a widget. It will be shown on your devices.

Constructor:

To utilize Dismissible, you need to call the constructor underneath:

You are required to pass the key (Key) and child (Widget). key turns out to be vital since the widget can be taken out from the widget list. If there are different dismissible widgets, ensure each has a unique key.

const Dismissible({
  required Key key,
  required this.child,
  this.background,
  this.secondaryBackground,
  this.confirmDismiss,
  this.onResize,
  this.onUpdate,
  this.onDismissed,
  this.direction = DismissDirection.horizontal,
  this.resizeDuration = const Duration(milliseconds: 300),
  this.dismissThresholds = const <DismissDirection, double>{},
  this.movementDuration = const Duration(milliseconds: 200),
  this.crossAxisEndOffset = 0.0,
  this.dragStartBehavior = DragStartBehavior.start,
  this.behavior = HitTestBehavior.opaque,
})

Be mindful not to involve the index as a key as dismissing a widget can change the index of different widgets. The second required property is a child where you want to pass the widget that can be dismissed.

Another significant property is onDismissed. It’s a callback function tolerating one boundary of type DismissDirection. Inside, you can characterize what to do after the widget has been dismissed. For instance, you can eliminate the widget from the list.

Properties:

There are some properties of Dismissible are:

> key — This property is used to control if it should be replaced.
> child — This property is used below this widget in the tree.
> background — This property is used to stack behind the child. It secondaryBackground is set, it’s only shown when the child is being dragged down or to the right.
> secondaryBackground — This property is used to stack behind the child. It’s only shown when the child is being dragged up or to the left.
> confirmDismiss— This property is used to allow the app to confirm or veto a pending dismissal.
> onResize — This property is used for the callback that will be called when the widget changes size.
> onDismissed — This property is used for the callback that will be called when the widget has been dismissed.
> direction — This property is used to the direction in which the widget can be dismissed. Defaults to DismissDirection.horizontal.
> resizeDuration — This property is used to the amount of time the widget will spend contracting before onDismissed is called. Defaults to const Duration(milliseconds: 300).
> dismissThresholds — This property is used to the offset threshold the item has to be dragged to be considered dismissed. Defaults to const <DismissDirection, double>{}.
> movementDuration — This property is used to the duration to dismiss or back to the original position if not dismissed. Defaults to const Duration(milliseconds: 200).
> crossAxisEndOffset — This property is used to the end offset across the main axis after the card is dismissed. Defaults to 0.0.
> dragStartBehavior — This property is used for how the drag start behavior is handled. Defaults to DragStartBehavior.start.

How to implement code in dart file :

You need to implement it in your code respectively:

Create a new dart file called main.dart inside the lib folder.

We will make a basic ListView where the thing can be dismissed. The ListView is made utilizing the accompanying values.

 List<String> items = [
    "Watch",
    "Jeans",
    "Shirt",
    "T-Shirt",
    "Cup",
    "Shoes",
    "Cap",
    "Shorts",
    "Trouser",
    "Lower",
  ];

Here is the code for building the ListView. The itemBuilder, which is utilized to construct the list of items, returns a Dismissible. Notwithstanding the required arguments (key and child), an onDismissed callback is additionally passed. The model tells you the best way to set various actions for every direction.

ListView.builder(
    itemCount: items.length,
    padding: const EdgeInsets.symmetric(vertical: 16),
    itemBuilder: (BuildContext context, index) {
      return Dismissible(
        key: Key('item ${items[index]}'),
        onDismissed: (DismissDirection direction) {
          if (direction == DismissDirection.startToEnd) {
            print("Add to favorite");
          } else {
            print('Remove item');
          }
 
          setState(() {
            items.removeAt(index);
          });
        },
        child: ListTile(
                leading: const Icon(
                  Icons.card_giftcard_rounded,
                  color: Colors.black,
                ),
                title: Text(
                  items[index],
                  style: TextStyle(
                      color: Colors.black.withOpacity(.6), fontSize: 18),
                ),
                subtitle: Text(
                  "This Gift is For you",
                  style: TextStyle(color: Colors.green.withOpacity(.6)),
                ),
              ),
      );
    }
  ),

When we run the application, we ought to get the screen’s output like the underneath screen capture.

> Showing Confirmation

Dismissible is frequently utilized for deleting an activity. On the off chance that you think the performed activity is critical and can’t be scattered, it’s smarter to show affirmation before the activity is characterized inside onDismissed is performed.

You can do it by passing confirmDismissCallback to the constructor. A callback acknowledges one parameter of type DismissDirection and returns Future<bool>. The below model shows an AlertDialog where the client can confirm to delete the item or cancel the action.

confirmDismiss: (DismissDirection direction) async {
    return await showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: const Text("Remove Gift"),
          content: const Text("Are you sure you want to remove this item?"),
          actions: <Widget>[
            ElevatedButton(
                onPressed: () => Navigator.of(context).pop(true),
                 child: const Text("Yes")),
            ElevatedButton(
                onPressed: () => Navigator.of(context).pop(false),
                child: const Text("No"),
             ),
          ],
        );
      },
    );
  }

> Setting Backgrounds

The default dismiss direction is horizontal. You can swipe to the right or left. Swiping left or right might result in an alternate action, relying upon what you characterize in the onDismissed callback. Flutter additionally permits you to set various widgets that will be shown when the child is being dismissed.

Utilize the background to characterize the widget to be shown when the child is swiped to the right and the secondary background for the widget when the child is swiped to the left. Assuming you just set the background, it will be utilized for the two directions.

background: Container(
  color: Colors.blue,
  child: Padding(
    padding: const EdgeInsets.all(15),
    child: Row(
      children: const [
        Icon(Icons.favorite, color: Colors.red),
        SizedBox(
          width: 8.0,
        ),
        Text('Move to favorites',
            style: TextStyle(color: Colors.white)),
      ],
    ),
  ),
),
secondaryBackground: Container(
  color: Colors.red,
  child: Padding(
    padding: const EdgeInsets.all(15),
    child: Row(
      mainAxisAlignment: MainAxisAlignment.end,
      children: const [
        Icon(Icons.delete, color: Colors.white),
        SizedBox(
          width: 8.0,
        ),
        Text('Move to trash',
            style: TextStyle(color: Colors.white)),
      ],
    ),
  ),
),

When we run the application, we ought to get the screen’s output like the underneath screen capture.

Code File:

import 'package:flutter/material.dart';
import 'package:flutter_dismissible_demo/splash_screen.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primarySwatch: Colors.teal,
      ),
      debugShowCheckedModeBanner: false,
      home: const Splash(),
    );
  }
}

class DismissibleDemo extends StatefulWidget {
  const DismissibleDemo({Key? key}) : super(key: key);

  @override
  State<DismissibleDemo> createState() => _DismissibleDemoState();
}

class _DismissibleDemoState extends State<DismissibleDemo> {
  List<String> items = [
    "Watch",
    "Jeans",
    "Shirt",
    "T-Shirt",
    "Cup",
    "Shoes",
    "Cap",
    "Shorts",
    "Trouser",
    "Lower",
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.teal,
          centerTitle: true,
          automaticallyImplyLeading: false,
          title: const Text("Flutter Dismissible Demo"),
        ),
        body: ListView.builder(
          itemCount: items.length,
          padding: const EdgeInsets.symmetric(vertical: 16),
          itemBuilder: (BuildContext context, int index) {
            return Dismissible(
              background: Container(
                color: Colors.blue,
                child: Padding(
                  padding: const EdgeInsets.all(15),
                  child: Row(
                    children: const [
                      Icon(Icons.favorite, color: Colors.red),
                      SizedBox(
                        width: 8.0,
                      ),
                      Text('Move to favorites',
                          style: TextStyle(color: Colors.white)),
                    ],
                  ),
                ),
              ),
              secondaryBackground: Container(
                color: Colors.red,
                child: Padding(
                  padding: const EdgeInsets.all(15),
                  child: Row(
                    mainAxisAlignment: MainAxisAlignment.end,
                    children: const [
                      Icon(Icons.delete, color: Colors.white),
                      SizedBox(
                        width: 8.0,
                      ),
                      Text('Move to trash',
                          style: TextStyle(color: Colors.white)),
                    ],
                  ),
                ),
              ),
              key: ValueKey<String>(items[index]),
              onDismissed: (DismissDirection direction) {
                setState(() {
                  items.removeAt(index);
                });
              },
              confirmDismiss: (DismissDirection direction) async {
                if (direction == DismissDirection.startToEnd) {
                  return await showDialog(
                    context: context,
                    builder: (BuildContext context) {
                      return AlertDialog(
                        title: const Text("Add Gift to Cart"),
                        content: const Text(
                            "Are you sure you want to add this gift in your cart"),
                        actions: <Widget>[
                          ElevatedButton(
                              onPressed: () => Navigator.of(context).pop(true),
                              child: const Text("Yes")),
                          ElevatedButton(
                            onPressed: () => Navigator.of(context).pop(false),
                            child: const Text("No"),
                          ),
                        ],
                      );
                    },
                  );
                } else {
                  return await showDialog(
                    context: context,
                    builder: (BuildContext context) {
                      return AlertDialog(
                        title: const Text("Remove Gift"),
                        content: const Text(
                            "Are you sure you want to remove this gift item?"),
                        actions: <Widget>[
                          ElevatedButton(
                              onPressed: () => Navigator.of(context).pop(true),
                              child: const Text("Yes")),
                          ElevatedButton(
                            onPressed: () => Navigator.of(context).pop(false),
                            child: const Text("No"),
                          ),
                        ],
                      );
                    },
                  );
                }
              },
              child: ListTile(
                leading: const Icon(
                  Icons.card_giftcard_rounded,
                  color: Colors.black,
                ),
                title: Text(
                  items[index],
                  style: TextStyle(
                      color: Colors.black.withOpacity(.6), fontSize: 18),
                ),
                subtitle: Text(
                  "This Gift is For you",
                  style: TextStyle(color: Colors.green.withOpacity(.6)),
                ),
              ),
            );
          },
        ));
  }
}

Conclusion:

In the article, I have explained the Dismissible basic structure in a flutter; you can modify this code according to your choice. This was a small introduction to Dismissible User Interaction from my side, and it’s working using Flutter.

I hope this blog will provide you with sufficient information on Trying the Dismissible in your flutter projects. We will show you what the Introduction is and what are the construction and properties of the Dismissible and make a demo program for working with Dismissible in your flutter applications. So please try it.

❤ ❤ Thanks for reading this article ❤❤

If I got something wrong? Let me know in the comments. I would love to improve.

Clap 👏 If this article helps you.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutter developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! You can connect with us on Facebook, GitHub, Twitter, and LinkedIn for any flutter-related queries.

We welcome feedback and hope you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Related: SMS Using Twilio In Flutter

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

How to Debug and Fix Errors in FlutterFlow Projects?

Error-fixing

Umesh Raghav

-

April 7, 2025

0

Debugging is an essential part of app development, and even though FlutterFlow simplifies the process, errors and issues can still arise. Understanding how to debug and fix errors effectively can save you time and frustration. This guide will cover common errors, debugging techniques, and solutions to ensure your FlutterFlow project runs smoothly.

1. Understanding Common Errors in FlutterFlow

Before diving into debugging, let’s look at some of the most common errors developers face when working with FlutterFlow:

a. API & Backend Issues

API calls failing due to incorrect endpoints, parameters, or authentication issues.
Incorrect Firebase database rules restricting access to read/write data.
Missing API keys or incorrect configurations.

b. UI & Navigation Errors

Widgets not displaying correctly due to layout issues.
Page navigation not working because of incorrect route settings.
Overlapping UI elements causing bad user experience.

c. State Management Issues

Data not updating in real-time due to improper Firestore integration.
Variables and states not persisting when switching pages.
Conditional visibility not working properly due to incorrect logic.

d. Performance & Optimization Issues

Slow app performance due to unoptimized images or inefficient queries.
Excessive API calls causing rate limits.
App crashes due to memory overload.

2. Debugging Tools in FlutterFlow

FlutterFlow provides built-in tools and third-party integrations to help debug your app efficiently.

a. Run/Test Mode in FlutterFlow

Use the Run Mode feature to preview your app and check for UI errors.
The Test Mode allows you to simulate API requests and check real-time data flow.

b. Debug Console & Error Logs

The debug console in FlutterFlow helps identify errors related to API calls, database connections, and UI rendering.
If your app crashes, check the error logs to find the exact issue.

c. Firebase Debugging

Use Firebase Emulator Suite to test Firestore, Authentication, and Functions locally.
Check Firebase Console → Logs for errors in authentication and Firestore queries.

d. Browser Console for Web Apps

If debugging a FlutterFlow web app, open the browser’s developer console (Chrome: Ctrl + Shift + I → Console tab) to check for warnings and errors.

3. Fixing Errors in FlutterFlow

a. Debugging API & Backend Issues

Problem: API call is not returning data.
Solution:

Check if the API endpoint URL is correct.
Verify that API headers and parameters match the API documentation.
Enable CORS if your API restricts cross-origin requests.
Use Postman or cURL to test the API before integrating it into FlutterFlow.

Problem: Firestore database data is not loading.
Solution:

Check Firebase rules (Firebase → Firestore → Rules). Example of an open rule:

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if true;
    }
  }
}

2. Verify that the Firestore collection name matches what you are using in FlutterFlow.

3. Enable Firebase logs to see database read/write failures.

b. Fixing UI & Navigation Errors

Problem: Button click doesn’t navigate to the next page.
Solution:

Check if the navigation action is correctly set (onClick → Navigate to Page).
Ensure the destination page exists in the project.
Use debug mode to inspect page transitions.

Problem: UI elements are not displaying correctly.
Solution:

Use Container → Debug Mode to inspect layouts.
Check padding, margin, and constraints to avoid overlapping.
Ensure visibility conditions are correct (if using conditional rendering).

c. Resolving State Management Issues

Problem: Data disappears when navigating between pages.
Solution:

Use App State variables instead of local state variables for persistent data.
Check if data is being cleared on navigation (avoid resetting variables unnecessarily).
Use Firestore Streams for real-time updates instead of manual fetches.

Problem: Toggle switch/button not updating UI correctly.
Solution:

Ensure the widget is connected to a state variable.
Use Set State Action to refresh UI elements dynamically.
If using Firestore, verify that data updates are reflected in real-time.

d. Fixing Performance & Optimization Issues

Problem: App is running slowly.
Solution:

Optimize Firestore queries by using where clauses to fetch only relevant data.
Reduce API calls by caching responses or using local state storage.
Compress images using WebP format instead of PNG/JPEG.

Problem: App is crashing unexpectedly.
Solution:

Open Flutter DevTools to check memory usage and leaks.
Enable error tracking in Firebase Crashlytics.
Check if any dependencies conflict with each other.

4. Best Practices to Avoid Errors in FlutterFlow

To prevent issues before they occur, follow these best practices:

a. Use Version Control

Always save different versions of your project in GitHub or Firebase Hosting.
Keep a backup before making major changes.

b. Test Features in Stages

Instead of building everything at once, test UI components and API calls separately.
Use FlutterFlow’s Run Mode frequently to check for early issues.

c. Follow Firebase & API Documentation

Read the official Firebase & API documentation before integrating them into your app.
Keep track of API updates to avoid deprecated methods.

d. Monitor Logs & Analytics

Use Google Analytics for Firebase to track user interactions and errors.
Regularly check Firestore logs for failed queries and permission issues.

Conclusion

Debugging in FlutterFlow is straightforward if you follow a structured approach. By identifying common errors, using built-in debugging tools, and applying best practices, you can quickly resolve issues and build a stable FlutterFlow app. Whether it’s fixing API issues, UI glitches, or performance problems, proper debugging will save time and enhance user experience.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutterflow developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

List Of Dates Between Two Given Dates In Flutter & Dart

Featured

Shaiq Khan

-

April 7, 2025

0

While creating applications with Flutter and Dart, there may be circumstances where you want to separate a list of dates between two given dates.

This article will explore the List Of Dates Between Two Given Dates In Flutter & Dart. We will perceive how to execute a demo program and we are going to learn about how we can use it in your applications.

If you’re looking for the best Flutter app development company for your mobile application then feel free to contact us at — support@flutterdevs.com.

Table Of Contents::

Using a For loop

Using List.generate()

Conclusion

Using a For loop:

In this underneath example, we’ll characterize a function named getDaysInBetween that takes two contentions, startDate, and endDate, and returns a list of dates between them including the limits.

The code:

List<DateTime> getDaysInBetween(DateTime startDate, DateTime endDate) {
  List<DateTime> days = [];
  for (int i = 0; i <= endDate.difference(startDate).inDays; i++) {
    days.add(startDate.add(Duration(days: i)));
  }
  return days;
}

// try it out
void main() {
  DateTime startDate = DateTime(2023, 5, 5);
  DateTime endDate = DateTime(2023, 5, 15);

  List<DateTime> days = getDaysInBetween(startDate, endDate);

  // print the result without time
  days.forEach((day) {
    print(day.toString().split(' ')[0]);
  });
}

When we run the application, we ought to get the screen’s output like the underneath screen Console Output.

2023-05-05
2023-05-06
2023-05-07
2023-05-08
2023-05-09
2023-05-10
2023-05-11
2023-05-12
2023-05-13
2023-05-14
2023-05-15

Process finished with exit code 0

Using List.generate():

You can get a list of dates between two given dates by utilizing the List.generate() technique and pass the number of days between the beginning and end date as the length parameter.

The code:

List<DateTime> getDaysInBetween(DateTime startDate, DateTime endDate) {
  final daysToGenerate = endDate.difference(startDate).inDays + 1;
  return List.generate(daysToGenerate, (i) => startDate.add(Duration(days: i)));
}

// try it out
void main() {
  DateTime startDate = DateTime(2023, 5, 10);
  DateTime endDate = DateTime(2023, 5, 15);

  List<DateTime> days = getDaysInBetween(startDate, endDate);

  // print the result without time
  days.forEach((day) {
    print(day.toString().split(' ')[0]);
  });
}

When we run the application, we ought to get the screen’s output like the underneath screen Console Output.

2023-05-11
2023-05-12
2023-05-13
2023-05-14
2023-05-15

Process finished with exit code 0

Conclusion:

In the article, I have explained the list of dates between two given dates in Flutter & Dart; you can modify this code according to your choice. This was a small introduction to List Of Dates Between Two Given Dates In Flutter & Dart User Interaction from my side, and it’s working using Flutter.

I hope this blog will provide you with sufficient information on Trying the List Of Dates Between Two Given Dates In Flutter & Dart of your projects. So please try it.

❤ ❤ Thanks for reading this article ❤❤

If I got something wrong? Let me know in the comments. I would love to improve.

Clap 👏 If this article helps you.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutter developer for your cross-platform Flutter mobile app project hourly or full-time as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy how you use Flutter to build beautiful, interactive web experiences.

By Shaiq khan on June 14, 2023.

Canonical link

Exported from Medium on December 4, 2023.

Related: Animated list In Flutter

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

FlutterFlow For MVP Development

Featured

Shaiq Khan

-

April 4, 2025

0

This blog will explore FlutterFlow for MVP development. How creating an MVP is made easier by FlutterFlow’s drag-and-drop interface, low-code platform, rapid prototyping, and many other notable features. We’ve covered the basics of developing an MVP, the primary justifications for using FlutterFlow, and a few successful company examples that have used this low-code approach.

If you’re looking for the best Flutter app development company for your mobile application then feel free to contact us at — support@flutterdevs.com.

Introduction:

Every company must validate its product idea in the rapidly evolving world of digital ecosystems before devoting a substantial amount of time and resources to the development phase. The idea of an MVP (Minimum Viable Product) enters the picture here. One of the best ways to test the functionality, potential, and user experience of your digital product before making a significant investment in full-fledged development is to build an MVP.

In order to lower the failure risk during product development, Proof of Concepts (PoCs) and Minimum Viable Products (MVPs) are frequently essential components. MVPs allow companies to quickly test their ideas in the market and get insightful feedback for future development. FlutterFlow stands out as a game-changer as developers and entrepreneurs look for useful frameworks and tools to create MVPs. It provides an affordable and aesthetically pleasing platform for MVP development.

Key Reasons:

A minimum viable product, or MVP, is the minimalist version of your product that only includes just enough features to validate the business idea and attract early adopters. It encompasses very limited features and functions essential to delivering value to first users and obtain enhancement feedback. Instead of investing many resources, fortune, and time into creating a fully developed product, it is favorable to create an MVP for mobile apps or websites to collect user feedback and validate market demand. These benefits include the following:

The bare minimum version of your product that has just enough features to verify the business concept and draw in early adopters is known as a minimum viable product, or MVP. It just includes the bare minimum of features and capabilities necessary to provide value to initial users and gather feedback for improvement. It is better to produce an MVP for websites or mobile apps to get user input and confirm market need rather than spending a lot of money, time, and resources on a fully developed product. Among these advantages are the following:

Idea Validation: Businesses may test and validate the features and potential of their applications in the real world with an MVP. It assists them in determining whether or not the target market will find their app idea appealing. Before investing in lengthy development, companies can evaluate user engagement and improve the product based on user feedback by releasing a basic and minimalistic version of the actual product.
Resource Efficiency: Businesses that think about creating a whole application from the ground up will have to spend a lot of money, time, and effort. But with MVP development, they can avoid failure risks and make efficient use of their resources.
Faster Time to Market: Developing an MVP undoubtedly aids companies in launching their products swiftly. Because MVPs can be created quickly, companies can outperform rivals who might still be bogged down in the process of creating a more comprehensive product.
Cost Efficiency: When developing an MVP, everything is kept clear and simple, from design to development. As a result, the MVP development cost is significantly reduced because the minimal viable product only has the functionality necessary to carry out key tasks. This economical strategy is especially beneficial for new businesses and entrepreneurs with tight funds.
Gathering User Feedback: Obtaining early user feedback is a primary motivation for developing an MVP. Businesses can find defects, learn about consumer preferences, and make sure that the product is improved to match user expectations by getting early feedback on the MVP.
Iterative Improvements: If you want a dependable framework for quick prototypes, iteration, and improvement, MVPs are your best bet. Based on customer experience and feedback, it enables companies to improve their product, address issues found, and make it more effective and efficient. Companies can succeed in this cutthroat industry by implementing this economical, iterative development strategy.

What is FlutterFlow?

One way to describe FlutterFlow is as a low-code development platform that facilitates quicker, easier, and more effective app creation. FlutterFlow, which is based on Google’s Flutter framework, enables fans to create web and mobile apps without the need for coding or development expertise. That means that because of its simple drag-and-drop feature, FlutterFlow may be used for MVP development by developers, designers, and even non-technical users who are not tech users.

Developers use FlutterFlow because of its cross-platform compatibility and quick MVP development process. Using a visual interface provided by this low-code/no-code platform, developers can create applications by rearranging text boxes and buttons on a screen. Furthermore, FlutterFlow is adaptable to both straightforward and intricate projects since it permits the insertion of unique Dart code. In addition to being compatible with Firebase, it provides capabilities like cloud storage, safe data management, real-time databases, and authentication to further expedite app development.

Why Choose FlutterFlow For MVP Development?

When developing a Minimum Viable Product (MVP), you must work quickly, strategically, and economically. And FlutterFlow, the low-code/no-code development ally, can help you accomplish it with ease. FlutterFlow is a robust platform that makes app development easier with its drag-and-drop tools, visual interface, and smooth integration features. Both experienced and novice developers can create MVPs in the low-code environment without having to worry about complicated coding. The following are the main justifications for selecting FlutterFlow for developing MVPs:

Drag and Drop Interface: FlutterFlow’s drag-and-drop interface, which enables users to construct intricate app user interfaces without writing a single line of code, is one of the main reasons to utilise it for MVP development. Components like buttons, text boxes, and images can be easily arranged on canvas by dragging and dropping them to create user interfaces that are easy to understand. This feature enables faster prototyping, making it easy for everyone, especially non-tech users, to start building apps.
10 Times Faster Development: Rapid iteration and development are essential when creating an MVP, and FlutterFlow is excellent at this. Compared to native application development, which uses a typical coding method, developers may produce MVPs 10 times faster with our low-code development platform. You can save a tonne of time by avoiding the need to create complicated code scripts thanks to the drag-and-drop feature, pre-made components, and simple deployment.
Visual Builder: One of FlutterFlow’s most useful features is its visual builder, which is why the majority of business owners choose this low-code/no-code platform to create MVPs. Users can design apps in real time and see the interface changes they make instantly with FlutterFlow’s user-friendly visual builder. Designing interactive prototypes that mimic the functionality and user experience of the real app will be much quicker.

Conclusion:

In the article, I have explained the FlutterFlow For MVP Development basic structure; you can modify this code according to your choice. This was a small introduction to the FlutterFlow For MVP Development On User Interaction from my side, and it’s working using Flutterflow.

I hope this blog will provide you with sufficient information on Trying FlutterFlow For MVP Development in your projects. For companies looking to create minimal viable products (MVPs), FlutterFlow is unquestionably revolutionary. FlutterFlow is a good choice for MVP development because of its user-friendly UI, drag-and-drop capabilities, large component libraries, and quick interaction with third-party APIs and backend providers like Firebase and Supabase. So please try it.

❤ ❤ Thanks for reading this article ❤❤

If I got something wrong? Let me know in the comments. I would love to improve.

Clap 👏 If this article helps you.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutterflow developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

Custom QR Code Generator in Flutterflow — Custom Widget

Widgets

Umesh Raghav

-

April 2, 2025

0

Custom QR Code Generator in Flutterflow — Custom Widget

QR codes offer a quick and convenient way to share data like URLs, contact information, Wi-Fi credentials, and more. By simply scanning a QR code with apps like Google Lens (Android), Apple Camera (iOS), or your own custom-built app, users can instantly access the embedded content.

In this guide, We’ll learn how to create a Custom QR Code Generator using Flutterflow. We’ll walk you through building a reusable widget that can be easily integrated into your FlutterFlow app. With customizable colors, shapes, you can generate QR codes that match your app’s style and branding!

Package overview

Here’s a Flutter package you can use to build your own QR code generator widget.

You can explore Flutter packages on pub.dev, the official package repository for Dart and Flutter. One popular and well-maintained option for generating QR codes is qr_flutter, known for its reliability and community support.

The package maintains strong metrics including Likes, Pub Points (up to 150), and a high Popularity rating (out of 100%). You can learn more about how these scores work here.
It also supports web, making it easy to preview and test your widget directly in FlutterFlow’s Run/Test mode.

Setup FlutterFlow

Go to FlutterFlow Website
Visit flutterflow.io and log in with your Google or GitHub account. If you don’t have an account, sign up for free.
Create a New Project

After logging in, click the “Create New” button on the Flutter Flow dashboard.
Choose “Blank App” or select from templates if you want a head start.

3. Name Your Project
Enter a name for your app and optionally add a project description.

4. Choose a Platform
Select the platforms you’re building for: Android, iOS, Web, or All.

5. Set Up Firebase (Optional but Recommended)

You can skip this for now or connect your Firebase project.
Firebase enables authentication, Firestore database, storage, and more.

6. Select a Layout
Choose a layout like mobile app, tablet, or web view based on your target platform.

7. Start Building Your App
Once inside the project, you can:

Drag and drop widgets from the UI builder
Add pages, components, and navigation
Connect backend APIs or Firebase
Use Custom Functions and Custom Widgets for advanced logic

8. Run/Test Your App

Use the Run/Test tab to preview your app in real-time on the web.
You can also use the FlutterFlow Preview App on mobile for live testing.

Defining the Custom Action

From the Navigation Menu (present on the left), select Custom Functions.
Go to the Custom Actions tab and click + Create.
Enter the action name as QrCode.
Add the package

Most well-known packages provide a simple usage example to help you get started quickly. On the qr_flutter package page, if you scroll down, you’ll find an Examples section. It includes a basic QR code generation snippet that serves as a great starting point for integrating the package into your app.

5. Add this Code in your Custom Code Widget.

// Automatic FlutterFlow imports
import '/flutter_flow/flutter_flow_theme.dart';
import '/flutter_flow/flutter_flow_util.dart';
import '/custom_code/widgets/index.dart';
import '/flutter_flow/custom_functions.dart';
import 'package:flutter/material.dart';
// Begin custom widget code
// DO NOT REMOVE OR MODIFY THE CODE ABOVE!

import 'package:qr_flutter/qr_flutter.dart';

import 'package:qr_flutter/qr_flutter.dart';

class QrCode extends StatefulWidget {
  const QrCode({
    super.key,
    this.width,
    this.height,
  });

  final double? width;
  final double? height;

  @override
  State<QrCode> createState() => _QrCodeState();
}

class _QrCodeState extends State<QrCode> {
  TextEditingController qrCodeController = TextEditingController();
  String qrData = '';

  @override
  void dispose() {
    qrCodeController.dispose();
    super.dispose();
  }

  void generateQrCode() {
    setState(() {
      qrData = qrCodeController.text;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Column(
        children: [
          TextFormField(
            controller: qrCodeController,
            decoration: InputDecoration(
                hintText: "Enter your text",
                hintStyle: TextStyle(
                  color: Colors.black,
                ),
                border: OutlineInputBorder(
                    borderSide: BorderSide(color: Colors.black, width: 1),
                    borderRadius: BorderRadius.circular(20))),
          ),
          const SizedBox(
            height: 50,
          ),

          QrImageView(
            data: qrData,
            version: QrVersions.auto,
            size: 300,
          ),
          const SizedBox(
            height: 50,
          ),
          Container(
            height: 50,
            width: 160,
            decoration: BoxDecoration(
              borderRadius: BorderRadius.circular(20),
              color: Colors.green,
            ),
            child: MaterialButton(
              onPressed: generateQrCode,
              child: Text("Generate Qr Code"),
            ),
          )
        ],
      ),
    );
  }
}

You can easily modify this code to support different types of QR code data such as URLs, phone numbers, email addresses, or even vCard/contact information. Instead of just plain text (like a name), predefined data formats allow users to generate QR codes that directly open links, dial numbers, or send emails when scanned. You can also enhance the UI with labels, validation, or by displaying the QR data below the code. Additionally, consider adding download or share functionality to improve usability.

6. After add this code then, Click the Save Button.

7. Go to the Widget Tree and click the add a click to this widget. Then navigate to the Components section, where you’ll find the custom widgets defined in your project. Locate the custom widget named “QrCode”, click on it to add it to your page, and design how you want it to appear within your layout.

8. Click the “Run” button at the top-right corner of the screen to start your FlutterFlow app.

The following shows the expression evaluation in action, running on an android emulator:

Output

Conclusion

The Custom QR Code Generator makes it easy to generate dynamic QR codes within your FlutterFlow app. Using the qr_flutter package, it ensures smooth rendering and user-friendly functionality. You can further enhance it by adding customization options, styling, or even QR scanning features to improve user experience.

References

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutterflow developer for your cross-platform Flutter mobile app project on an hourly or full-time basis as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

Implementing Multimedia Ads In Flutter

Featured

Ritutosh Bhatia

-

April 1, 2025

0

Introduction

Monetizing a Flutter app effectively requires integrating ads without compromising the user experience. Multimedia ads, including banner, interstitial, rewarded, and native ads, offer various ways to generate revenue. Google AdMob, Facebook Audience Network, and other third-party ad networks provide SDKs for integrating ads into Flutter apps.

This guide covers everything from setting up ad networks to implementing different ad types in Flutter, ensuring a smooth and optimized experience for developers and users.

If you’re looking for the best Flutter app development company for your mobile application then feel free to contact us at — support@flutterdevs.com.

AdMob is a mobile advertising platform by Google that allows app developers to monetize their apps through various ad formats, including banner ads, interstitial ads, rewarded videos, and native ads. It offers high fill rates, intelligent mediation, and detailed performance analytics, making it one of the most popular choices for app monetization.

Key Features:

High fill rates and competitive CPMs
Supports multiple ad formats
Advanced mediation for optimizing ad revenue
Integration with Google Analytics for performance tracking

Do You Need AdMob in Flutter for Ads?

AdMob is not mandatory for displaying ads in a Flutter app, but it is one of the most effective and widely used ad networks. If you want global reach, high fill rates, and seamless mediation, AdMob is a strong choice.

When to Use AdMob:

If you want a reliable and high-paying ad network
If your app targets a global audience
If you prefer Google’s ecosystem for analytics and optimization

When Not to Use AdMob:

If your app is focused on gaming (Unity Ads or AppLovin might be better)
If you have a social media-style app (Facebook Audience Network could be a good fit)
If you need aggressive ad mediation and optimization (IronSource excels in this area)

4. Setting Up AdMob in Flutter

Step 1: Create an AdMob Account

Go to AdMob and sign up.
Create a new app and register your Flutter app.
Generate Ad Unit IDs for different ad formats.

Step 2: Add AdMob Dependencies

Add the google_mobile_ads package to your Flutter project:

dependencies:
  google_mobile_ads: ^3.0.0

Run:

flutter pub get

Step 3: Initialize AdMob in `main.dart`

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  MobileAds.instance.initialize();
  runApp(MyApp());
}

5. Implementing Different Types of Ads in Flutter

1. Banner Ads (Static ads at the screen’s top/bottom)

BannerAd myBanner = BannerAd(
  adUnitId: 'your-ad-unit-id',
  size: AdSize.banner,
  request: AdRequest(),
  listener: BannerAdListener(),
);

Container(
  alignment: Alignment.bottomCenter,
  child: AdWidget(ad: myBanner),
  width: myBanner.size.width.toDouble(),
  height: myBanner.size.height.toDouble(),
)

2. Interstitial Ads (Full-screen ads between content)

InterstitialAd.load(
  adUnitId: 'your-ad-unit-id',
  request: AdRequest(),
  adLoadCallback: InterstitialAdLoadCallback(
    onAdLoaded: (InterstitialAd ad) {
      ad.show();
    },
    onAdFailedToLoad: (LoadAdError error) {
      print('Interstitial failed: $error');
    },
  ),
);

3. Rewarded Ads (Users earn rewards after watching an ad)

RewardedAd.load(
  adUnitId: 'your-ad-unit-id',
  request: AdRequest(),
  rewardedAdLoadCallback: RewardedAdLoadCallback(
    onAdLoaded: (RewardedAd ad) {
      ad.show(onUserEarnedReward: (AdWithoutView ad, RewardItem reward) {
        print("Reward earned: ${reward.amount}");
      });
    },
    onAdFailedToLoad: (LoadAdError error) {
      print('Rewarded Ad failed to load: $error');
    },
  ),
);

4. Native Ads (Ads that blend into app UI)

NativeAd(
  adUnitId: 'your-ad-unit-id',
  factoryId: 'adFactoryExample',
  listener: NativeAdListener(),
  request: AdRequest(),
);

Best Practices for Ad Integration

Preload Ads — Load ads in advance to minimize user wait time.

Non-Intrusive Placement — Position ads in a way that doesn’t disrupt user interactions.

Rewarded Ads Over Interstitials — Encourage engagement by offering users something in return.

Ad-Free Premium Version — Provide users with an option to remove ads through an in-app purchase.

6. Testing Ads in Flutter

Using Test Ad Unit IDs

To prevent policy violations, Google AdMob provides test Ad Unit IDs. These should be used during development:

Use test Ad Unit IDs to prevent accidental ad revenue violations.

Example test IDs:

Banner: ca-app-pub-3940256099942544/6300978111
Interstitial: ca-app-pub-3940256099942544/1033173712
Rewarded: ca-app-pub-3940256099942544/5224354917

const String testBannerAdUnitId = 'ca-app-pub-3940256099942544/6300978111';

Troubleshooting Common Issues

Ads not appearing — Ensure correct Ad Unit IDs and verify an active internet connection.
Crashes on startup — Initialize google_mobile_ads before attempting to load ads.
Interstitial Ads not displaying — Make sure the ad is fully loaded before calling .show().

7. Limitations of Multimedia Ads in Flutter

Common Challenges & Solutions

Ads failing to load — Verify proper configuration and use test ads during development.
User complaints about intrusive ads — Implement a balanced ad frequency strategy.
Revenue inconsistencies — Experiment with different ad placements to optimize engagement.

8. Platform-Specific Limitations

iOS App Store Policies

Apple enforces strict regulations against intrusive advertising.
Apps with excessive pop-up ads may face rejection from the App Store.

Google Play Compliance

Apps must adhere to Google’s Better Ads Standards.
Misplaced or disruptive ads can lead to app suspension.

9. Enhancing Ad Performance & Future Trends

Strategies for Maximizing Ad Revenue

A/B Testing — Test different ad placements to improve conversion rates.
Controlled Ad Frequency — Avoid overwhelming users with excessive advertisements.
Personalized Ad Experience — Provide an ad-free experience via a paid subscription.
Strategic Ad Timing — Display ads at logical transition points.

Emerging Trends in Ad Monetization

AI-powered ad Targeting — Uses machine learning to optimize ad delivery.
Augmented Reality (AR) & Virtual Reality (VR) Ads — More immersive advertising experiences.
Blockchain-Based Ad Networks — A decentralized approach for greater transparency.
Server-Side Ad Mediation — Dynamically switching between multiple ad networks to maximize revenue.

10. Conclusion

Multimedia ads are a powerful monetization tool for Flutter applications, but they must be implemented thoughtfully to maintain a positive user experience.

Key Takeaways:

Utilize Google AdMob or alternative networks for ad integration.
Implemented various ad formats effectively, including banner, interstitial, rewarded, and native ads.
Follow best practices to balance user engagement and revenue generation.
Stay updated with emerging trends to enhance ad monetization strategies.

You can maximize revenue by leveraging smart ad placements, adhering to platform policies, and optimizing performance while keeping your users engaged.

11. Reference

Get started | Flutter | Google for Developers
A mobile ads SDK for AdMob publishers who are building Flutter apps.developers.google.com

Add ads to your mobile Flutter app or game
How to use the google_mobile_ads package to show ads in Flutter.docs.flutter.dev

❤ ❤ Thanks for reading this article ❤❤

If I got something wrong? Let me know in the comments. I would love to improve.

Clap 👏 If this article helps you.

From Our Parent Company Aeologic

Aeologic Technologies is a leading AI-driven digital transformation company in India, helping businesses unlock growth with AI automation, IoT solutions, and custom web & mobile app development. We also specialize in AIDC solutions and technical manpower augmentation, offering end-to-end support from strategy and design to deployment and optimization.

Trusted across industries like manufacturing, healthcare, logistics, BFSI, and smart cities, Aeologic combines innovation with deep industry expertise to deliver future-ready solutions.

Feel free to connect with us:
And read more articles from FlutterDevs.com.

FlutterDevs team of Flutter developers to build high-quality and functionally-rich apps. Hire Flutter developer for your cross-platform Flutter mobile app project hourly or full-time as per your requirement! For any flutter-related queries, you can connect with us on Facebook, GitHub, Twitter, and LinkedIn.

We welcome feedback and hope that you share what you’re working on using #FlutterDevs. We truly enjoy seeing how you use Flutter to build beautiful, interactive web experiences.

Need expert help building your Flutter app? Talk to FlutterExperts for architecture, development, and consulting support.

Table Of Contents::

What is the Decorator Design Pattern?:

When to use?:

Code Implement:

Drawbacks:

Conclusion:

Table Of Contents:

Introduction:

Constructor:

Properties:

Implementation:

How to implement code in dart file :

Code File:

Conclusion:

GitHub Link:

Introduction

Table of Contents

1. Setting Up Stripe for Subscriptions

Step 1.1: Create a Stripe Account

Step 1.2: Enable Stripe Billing and Create a Subscription Product

2. Integrating Stripe Subscriptions in Flutter

Step 2.1: Install Required Dependencies

Step 2.2: Initialize Stripe in Flutter

Step 2.3: Setting Up a Backend for Subscription Management

Step 2.4: Handling Subscription Payment in Flutter

Step 2.5: Managing Subscriptions (Cancellation & Modifications)

3. Limitations of Stripe Subscriptions

4. Best Practices for Subscription Implementation

5. Future Scope of Subscription Payments

6. Conclusion

7. Reference

What is State in FlutterFlow?

🛠Types of State Management in FlutterFlow

1. Local State (UI State)

Example:

2. App State (Global State)

Example:

3. Firebase-Connected State

Example:

4. Custom Functions (Advanced State Updates)

5. Bloc Pattern (For Advanced Flutter Developers)

How to Use State Variables in FlutterFlow Step-by-Step:

1. Create a State Variable

2. Update the State

3. Bind State to Widgets

4. Observe State Changes

Real-Life Use Cases

Best Practices

Conclusion

Table Of Contents::

Introduction:

Constructor:

Properties:

How to implement code in dart file :

> Showing Confirmation

> Setting Backgrounds

Code File:

Conclusion:

1. Understanding Common Errors in FlutterFlow

a. API & Backend Issues

b. UI & Navigation Errors

c. State Management Issues

d. Performance & Optimization Issues

2. Debugging Tools in FlutterFlow

a. Run/Test Mode in FlutterFlow

b. Debug Console & Error Logs

c. Firebase Debugging

d. Browser Console for Web Apps

3. Fixing Errors in FlutterFlow

a. Debugging API & Backend Issues

b. Fixing UI & Navigation Errors

c. Resolving State Management Issues

d. Fixing Performance & Optimization Issues

4. Best Practices to Avoid Errors in FlutterFlow

a. Use Version Control

b. Test Features in Stages

c. Follow Firebase & API Documentation

d. Monitor Logs & Analytics

Conclusion

Table Of Contents::

Step 3: Initialize AdMob in `main.dart`