Flutter has been gaining immense popularity in recent times, and for a good reason. It is a powerful open-source mobile app development framework created by Google. It enables developers to build beautiful, fast, and high-performing native apps for Android, iOS, and web platforms with a single codebase.

If you’re an aspiring app developer preparing for a job interview, it’s important to have a clear understanding of the most commonly asked Flutter interview questions and answers. In this comprehensive blog post, we have covered the top interview questions on Flutter and Dart.

It also includes coding-based and MCQ-type questions, along with their answers, to help you prepare effectively and confidently for your interview.

You might already know that Flutter is a trending technology, and the demand for skilled Flutter developers is on the rise. This has resulted in a surge in high-paying career opportunities for Flutter developers worldwide. As a developer, mastering Flutter can be your ticket to a fulfilling and lucrative career in the tech industry.

So, whether you’re a beginner or an experienced developer, our write-up on top Flutter interview questions will help you get a head start in your interview preparation and pave the way for a successful career in this field.

Important Flutter Interview Topics

Here are some common topics that will come up in an interview for a Flutter developer position:

1. Flutter basics

Understanding of the basic building blocks of Flutter, such as widgets, stateful and stateless widgets, and Flutter architecture.

2. Dart programming

Knowledge of Dart programming language, including variables, data types, functions, and object-oriented programming concepts.

3. User interface design

Ability to create custom UI elements using Flutter widgets and layouts, and knowledge of material design principles.

4. Flutter libraries and packages

Familiarity with popular Flutter packages and libraries such as provider, http, and flutter_bloc.

5. State management

Understanding of state management techniques such as setState, InheritedWidget, BLoC, Provider, MobX, and Redux.

6. Navigation

Knowledge of Flutter’s navigation system and how to create and manage routes and screens.

7. Debugging and testing

Ability to debug and test Flutter apps using tools like Dart DevTools, Flutter Inspector, and Flutter Driver.

8. Platform integration

Understanding of how to integrate Flutter apps with native device features like camera, geolocation, and push notifications.

9. Performance optimization 

Familiarity with optimizing Flutter app performance using techniques such as lazy loading, caching, and asynchronous programming.

10. Deployment

Knowledge of how to build and deploy Flutter apps for Android, iOS, and web platforms.

Flutter Interview Questions for Freshers

If you’re a beginner, here is a list of Flutter interview questions and answers for freshers. Additionally, taking a Flutter online course will also be beneficial in strengthening your fundamentals and gaining practical experience.

1. What is Flutter?

Flutter is a framework for developing apps. It is an open-source framework developed by Google. It enables developers to create apps that are natively compiled for mobile, web, and desktop platforms, all from a single codebase.

Flutter also comes with a rich set of customizable pre-built widgets that can be used to create beautiful and responsive user interfaces. Developers can also create their own custom widgets to meet their specific needs.

2. What are the benefits of using Flutter?

There are several benefits to using Flutter for app development:

a) Fast development

Flutter allows for faster development cycles with its hot reload feature, which allows developers to see the effects of changes made to the code instantly. This can greatly reduce the overall development time and make it easier to iterate on the design and functionality of an app.

b) Write once and deploy across multiple platforms

With Flutter, developers can write code once and deploy it across multiple platforms such as iOS, Android, web, and desktop. 

This saves time and resources that would otherwise be spent on developing separate codebases for each platform.

c) Appealing UI 

Flutter offers a rich set of customizable widgets that allow developers to create beautiful and engaging user interfaces. It also provides a range of animations and effects that can help make an app feel more responsive and interactive.

d) High-performance

Flutter apps are built using Dart, which compiles to native code for high performance on each platform. This results in faster app startup times, smoother animations, and better overall performance.

e) Easy to learn

Flutter’s simplicity and ease of use make it accessible to both experienced and new developers. It has clear and concise documentation, along with a large community of developers who contribute to its development and support each other. One can easily learn it with a Flutter course.

3. What are the key features of Flutter?

Here are some key features of Flutter:

a) Widgets

There is a rich set of customizable widgets that can be used to build beautiful and responsive user interfaces for mobile, web, and desktop platforms. These widgets can be easily combined to create complex and interactive interfaces.

b) Hot Reload

This feature allows developers to instantly see the effects of changes made to the code without having to rebuild the entire app. This reduces development time and makes it easier to iterate on the design and functionality of an app.

c) Dart programming language

Flutter uses the Dart programming language, which is optimized for client-side development and provides a range of features such as optional typing and garbage collection. 

d) Cross-platform development

Flutter allows developers to write code once and deploy it across multiple platforms such as iOS, Android, web, and desktop. This can save time and resources that would otherwise be spent on developing separate codebases for each platform.

e) Material Design and Cupertino widgets

Flutter provides Material Design and Cupertino widgets, which are designed to match the look and feel of Android and iOS, respectively. This makes it easy to create apps that feel native on each platform.

f) Animation and Graphics

Flutter offers a powerful set of tools for creating animations and graphics, including support for 2D and 3D rendering, vector graphics, and a range of animation options.

4. What does cross-platform development mean?

Cross-platform development refers to the process of creating apps that can run on multiple platforms or operating systems using a single codebase. 

It has become increasingly popular in recent years, as it allows developers to reach a larger audience while minimizing development time and cost. 

Suggested Reading: Angular Interview Questions and Answers

5. Which programming language is used by Flutter?

Flutter uses the Dart programming language, which was created by Google. 

Dart is an object-oriented, client-optimized language that was designed to be easy to learn, efficient, and scalable. It was specifically created for building web and mobile applications, and it provides features such as optional typing and garbage collection.

It is a compiled language, which means that it is translated into machine code at runtime. This allows for high-performance execution of Dart code, making it well-suited for mobile app development.

6. How does Flutter render graphics?

Flutter uses a high-performance, GPU-accelerated rendering engine called Skia to render graphics. 

Skia is an open-source, 2D graphics library that is used by several other software applications, including Google Chrome and Android.

When an app is built using Flutter, the Flutter framework compiles the Dart code into native code for the target platform. This native code then communicates with Skia to render graphics on the screen.

Skia uses a retained mode graphics API, which means that it maintains a persistent object representation of the graphics being rendered. This allows for more efficient rendering, as objects can be reused and modified without having to be recreated from scratch each time. 

Moreover, Skia also provides a range of features, such as anti-aliasing, text rendering, and image processing, which can help create high-quality and visually appealing graphics.

7. What is a widget in Flutter?

A widget is a basic building block used to construct user interfaces. Widgets are used to create an app’s visual and interactive elements, such as buttons, text fields, images, and more. 

In Flutter, everything is a widget, including the app itself, the app’s layout, and the individual elements that make up the layout.

Widgets can be either stateless or stateful. 

• Stateless widgets are immutable, meaning they do not change over time. These widgets are used to create elements that do not change, such as text labels or icons. 

• Stateful widgets, on the other hand, can change over time. These widgets are used to create elements that respond to user interaction or other events, such as buttons or text fields.

8. What are the limitations of Flutter?

While Flutter is a powerful and flexible framework for building mobile apps, it does have some limitations that developers should be aware of:

a) Smaller community

Compared to other popular frameworks like React Native and Xamarin, the Flutter community is relatively small. This means that finding support and resources can be more challenging, and finding developers with experience in the framework may be harder.

b) Large app size

Because Flutter includes its own rendering engine and widget library, apps built with Flutter tend to be larger in size than those built with other frameworks. This can be a concern for users who have limited storage space on their devices.

c) Limited platform support

While Flutter supports multiple platforms, including iOS, Android, web, and desktop, it does not support as many platforms as some other frameworks. For example, it does not currently support wearable devices or TV platforms.

d) Limited native functionality

While Flutter provides a wide range of built-in widgets and libraries, there may be certain native functionality that is not available or more challenging to implement in Flutter. In some cases, developers may need to use platform-specific code to access certain native features.

e) Learning curve

While Dart, the language used by Flutter, is easy to learn, developers unfamiliar with reactive programming or the widget-based architecture of Flutter may face a steep learning curve when getting started with the framework.

9. What is the difference between hot reload and hot restart in Flutter?

Here is a well-structured table showing the differences between hot reload and hot restart:

10. What is the pubspec.yaml file in Flutter?

The pubspec.yaml file is a configuration file that contains metadata about your app or package, including the dependencies, assets, and other settings. 

It’s used by the Flutter package manager, called “pub”, to manage the dependencies of your app and download them from the internet.

Key components of pubspec.yaml file

Here are some key components of a typical pubspec.yaml file:

• name: The name of your app or package, which should be unique and easy to remember.
• description: A short description of your app or package.
• version: The current version of your app or package.
• dependencies: A list of packages that your app or package depends on, along with their versions.
• dev_dependencies: A list of packages that your app or package depends on only for development purposes, such as testing or documentation.
• flutter: A section that contains settings specific to Flutter, such as the SDK version and the assets used in the app.

Example of pubspec.yaml file

Here’s an example of a pubspec.yaml file for a Flutter app that depends on the http and flutter_bloc packages:

name: my_app

description: A sample Flutter app

version: 1.0.0

dependencies:

  http: ^0.13.4

  flutter_bloc: ^7.4.1

dev_dependencies:

  flutter_test:

    sdk: flutter

flutter:

  assets:

    - assets/images/

By including this file in your Flutter project, you can easily manage and track your app’s dependencies and assets, making it easier to develop and maintain your app over time. Be prepared for such concepts, because it is one of the top Flutter interview questions. 

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11. What is MaterialApp widget in Flutter?

MaterialApp is a widget in Flutter that implements the Material Design language, which is a visual language developed by Google that provides a consistent look and feel across all platforms and devices. 

This widget provides several important features to your Flutter app, including:

• A default theme that provides a consistent look and feel for all widgets in your app.
• Navigation and routing management, which makes it easy to move between different screens or pages in your app.
• Localization support, which allows you to translate your app into different languages.
• Support for displaying dialogs and snackbars, which are common UI components in many apps.

It is yet another important Flutter interview question to prepare for. 

12. What is Scaffold widget in Flutter?

Scaffold is a widget that provides a basic layout structure for your app. It is typically used as the top-level widget in your app and provides a number of useful features, including:

• A built-in app bar that displays the app’s title and can contain buttons for navigating to other screens or performing actions.
• A drawer widget that can be used to provide navigation to other parts of the app.
• A floating action button (FAB) that is often used for triggering important actions or for adding new content.
• A bottom navigation bar for switching between different sections of the app.

The Scaffold widget is a convenient way to quickly build the basic structure of your app, and it can be customized to fit your specific needs. 

For example, you can customize the app bar with a custom logo, add additional buttons to the FAB, or customize the appearance of the bottom navigation bar. 

In addition, this widget can be combined with other widgets to create more complex layouts, such as tabbed interfaces or scrolling lists. It is one of the most asked Flutter interview questions for answers. 

13. What is FutureBuilder widget in Flutter?

FutureBuilder is a widget that allows you to asynchronously build your UI based on the result of a future computation. It is commonly used when your UI depends on data that is being loaded asynchronously, such as data from an API or a database.

Working of FutureBuilder Widget

Here’s how it works:

• You create a Future object that represents the asynchronous computation that will eventually provide the data you need.
• You pass this Future to the FutureBuilder widget, which will wait for the future to complete and then rebuild the UI with the data that is returned.
• While the future is still being processed, FutureBuilder can display a loading indicator or placeholder widget.

Example 

Here’s an example of how to use FutureBuilder:

FutureBuilder(

  future: getData(),

  builder: (context, snapshot) {

    if (snapshot.hasData) {

      return Text(snapshot.data);

    } else if (snapshot.hasError) {

      return Text('Error: ${snapshot.error}');

    } else {

      return CircularProgressIndicator();

    }

  },

);

Here, getData() is a function that returns a Future that eventually provides a string value. The builder function takes two arguments: the current BuildContext and a snapshot object that contains the current state of the Future. 

If the snapshot has data, it displays the data using a Text widget. If there is an error, it displays an error message. Otherwise, it displays a CircularProgressIndicator widget to indicate that the data is still being loaded.

This topic is important to prepare for both beginners and experienced. For instance, if you are looking for Flutter interview questions for 1 year experience, then it is a relevant topic to prepare for. 

14. What is a stream in Flutter?

A stream is a sequence of asynchronous events that can be processed one at a time. It’s a way to handle and manipulate data that is being continuously updated or changed over time, such as user input, network data, or data from sensors.

Streams can be used to handle asynchronous data by providing a way to receive new data as soon as it becomes available. Streams work by sending a sequence of events to a listener, which can then react to each event as it arrives.

In Flutter, the Stream class represents a stream of data, and the StreamBuilder widget can be used to listen to and process the data in the stream. 

Example of Flutter stream:

Here’s an example of using a StreamBuilder to listen to a stream of data and display it in a Text widget:

Stream countStream() async* {

  int count = 0;

  while (true) {

    await Future.delayed(Duration(seconds: 1));

    yield count++;

  }

}

class MyApp extends StatelessWidget {

  @override

  Widget build(BuildContext context) {

    return MaterialApp(

      home: Scaffold(

        body: Center(

          child: StreamBuilder(

            stream: countStream(),

            builder: (context, snapshot) {

              if (snapshot.hasData) {

                return Text('Count: ${snapshot.data}');

              } else {

                return CircularProgressIndicator();

              }

            },

          ),

        ),

      ),

    );

  }

}

Here, countStream() is a function that returns a Stream that increments a counter every second. The StreamBuilder listens to this stream and updates the UI with the latest value of the counter. If there is no data yet, it displays a CircularProgressIndicator widget.

15. What is the purpose of the ListView widget in Flutter?

The ListView widget in Flutter is used to display a scrolling list of widgets. It is a powerful and flexible widget that can be used to display a wide range of data, from simple text to complex custom widgets.

The purpose of the ListView widget is to provide a way to display a large amount of data in a limited amount of space. It allows users to scroll through the data and see more content than would be possible with a fixed-size container. The ListView widget can be used to display a variety of data types, such as text, images, icons, and custom widgets.

Features of ListView widget

In addition to providing scrolling functionality, the ListView widget also provides several features to improve the user experience, such as:

• Lazy loading: the ability to load and display only the data that is currently visible on the screen, which can improve performance and reduce memory usage.
• Infinite scrolling: the ability to load more data as the user scrolls down the list, which can provide a seamless and uninterrupted browsing experience.
• Separators: the ability to display separators between list items to improve readability and distinguish between different items.

Example of ListView widget:

Here’s an example of using the ListView widget to display a list of items:

class MyApp extends StatelessWidget {

  final List items = ['Item 1', 'Item 2', 'Item 3', 'Item 4', 'Item 5'];

  @override

  Widget build(BuildContext context) {

    return MaterialApp(

      home: Scaffold(

        appBar: AppBar(

          title: Text('ListView Example'),

        ),

        body: ListView.builder(

          itemCount: items.length,

          itemBuilder: (context, index) {

            return ListTile(

              title: Text(items[index]),

            );

          },

        ),

      ),

    );

  }

}

Here, we define a list of items and use the ListView.builder constructor to display them in a scrolling list. The itemCount property specifies the number of items in the list, and the itemBuilder function is called for each item to build a ListTile widget that displays the item’s text.

16. What is the difference between mainAxisAlignment and crossAxisAlignment in Flutter?

Both mainAxisAlignment and crossAxisAlignment are properties of widgets that are used to align child widgets within their parent widget. The main axis is defined as the primary axis of the parent widget, while the cross axis is defined as the axis perpendicular to the main axis.

Here’s a comparison table to highlight the differences between mainAxisAlignment and crossAxisAlignment:

17. What is the difference between InkWell and GestureDetector in Flutter?

In Flutter, both InkWell and GestureDetector widgets are used to detect user gestures on a widget. They both provide similar functionality, but there are some key differences between the two. 

InkWell:

• A Material design widget that provides a visual splash effect when the user taps on it.
• Best used on Material design surfaces, when the user needs to visually confirm their touch input.
• Provides a visual ink splash effect when tapped, which can be customized with the splashColor, highlightColor, and radius properties.
• Requires a Material design parent widget, such as Material, Scaffold, or Card, in order to work correctly.

GestureDetector:

• A general-purpose widget that can detect various user gestures, such as taps, drags, and long presses.
• Best used for custom gestures or non-material design interfaces.
• Provides no visual feedback by default, but can be customized with the feedback property.
• Does not require a Material design parent widget, and can be used on any type of widget.

Here’s a comparison table highlighting the differences:

Flutter Interview Questions for Experienced Developer

Below is the list of Flutter interview questions and answers for experienced professionals. It will help you brush up on advanced concepts and stay up-to-date with the latest industry trends. 

With our comprehensive guide, you can ensure that you are well-prepared to tackle any question that comes your way during your interview.

18. Why Flutter uses Dart?

Flutter uses Dart as its primary programming language for a number of reasons:

a) High performance 

Dart is optimized for performance, with features like just-in-time (JIT) and ahead-of-time (AOT) compilation. This makes it ideal for creating high-performance, fast-loading apps.

b) Familiar syntax

Dart has a familiar syntax that is similar to other popular programming languages like Java and JavaScript, making it easier for developers to learn and write code in Dart.

c) Strong typing

Dart is a strongly typed language, which means that variables and function return types must be explicitly defined. This helps prevent bugs and makes code easier to read and understand.

d) Built-in support for asynchronous programming

Dart has built-in support for asynchronous programming, making it easier for developers to write code that runs efficiently on mobile devices.

e) Single codebase

With Dart and Flutter, developers can build native apps for both iOS and Android platforms using a single codebase. This can help reduce development time and costs, while also making it easier to maintain and update the app over time.

f) Open source

Dart is an open-source programming language. It is freely available and can be modified and improved by developers around the world. This helps ensure that the language and associated tools remain up-to-date and relevant.

Learn DART for Flutter | What is Dart Programming? | Dart Programming Language

19. What are packages and plugins in Flutter?

Packages and plugins are ways to add pre-built functionality to your app.

Packages 

These are collections of Dart code that provide reusable functionality, such as widgets, APIs, and other utility classes. 

These can be created by anyone and shared through the Dart package repository, Pub. To use a package in your app, you simply need to add a dependency to it in your pubspec.yaml file and run flutter pub get to download and install it.

Plugins

On the other hand, plugins are similar to packages but provide native code functionality for specific platforms such as iOS and Android. These allow you to access native platform APIs, such as camera, geolocation, and Bluetooth, from your Flutter app. 

Plugins are created by the Flutter community and can be found in the Flutter plugins repository. To use a plugin in your app, you need to add a dependency to it in your pubspec.yaml file and import it in your Dart code.

It is one of the most important Flutter developer interview questions in 2023. So prepare well for it.

20. Explain the different build modes in Flutter.

Flutter provides different build modes that allow developers to optimize their app for specific scenarios. 

The three build modes are:

i) Debug mode

This is the default mode used during development. In debug mode, the app is compiled with additional debugging information, and hot-reload and hot-restart are available. 

This mode is slower than release mode, but it provides better error messages and makes it easier to diagnose and fix issues during development.

ii) Profile mode 

In profile mode, the app is optimized for performance, with extra diagnostic information and profiling enabled. This mode is faster than debug mode, but it still allows developers to track down issues that may not be evident in release mode.

iii) Release mode

This is the final mode used for production releases. In release mode, the app is compiled with maximum optimization and without debugging information. 

This mode produces the fastest and smallest possible code, which is ideal for distributing the app to end users. However, it also means that debugging tools like hot-reload are not available, and errors may be harder to diagnose.

Here’s a summary of the different build modes in Flutter:

Suggested Reading: NodeJS Interview Questions and Answers

21. Which are the best editors for Flutter?

Flutter can be developed using a variety of text editors and integrated development environments (IDEs), depending on personal preferences and project requirements. 

Here are some popular options:

a) Android Studio

It is the official IDE for Android development, and it has excellent support for Flutter. Android Studio includes features like code completion, debugging, and hot-reload. It is also integrated with the Flutter SDK and offers tools for building, testing, and deploying apps.

b) Visual Studio Code 

It is a lightweight and versatile code editor that offers great support for Flutter development. Visual Studio Code includes a range of extensions for Flutter, such as code completion, debugging, and hot-reload. It is also customizable and supports many programming languages.

c) IntelliJ IDEA

It is a popular Java IDE that also offers excellent support for Flutter development. IntelliJ IDEA provides features like code completion, debugging, and hot-reload. It is also customizable and supports many programming languages.

d) Emacs 

It is a powerful and customizable text editor that supports Flutter development. Emacs offers features like syntax highlighting, code completion, and debugging, and it can be extended with many plugins.

e) Sublime Text

Sublime Text is a lightweight and customizable text editor that supports Flutter development. It includes features like syntax highlighting, code completion, and debugging, and it can be customized with many plugins.

While preparing for Flutter interview questions, you must have a clear idea of the top editors and how to use them. 

22. Which are the most popular apps that use Flutter?

Flutter has gained popularity among developers due to its ease of use, cross-platform capabilities, and rich set of features. 

Here are some popular apps that have been built using Flutter:

a) Google Ads

Google Ads is a mobile app for managing Google Ads campaigns. It was built using Flutter and offers a smooth and responsive user experience.

b) Alibaba

Alibaba, the popular e-commerce platform, used Flutter to develop its Xianyu app, which offers a secondhand marketplace for users in China.

c) Reflectly

Reflectly is a mindfulness app that uses Flutter for its mobile interface. It offers a clean and user-friendly design, with features like journaling and personalized mindfulness exercises.

d) Realtor.com

Realtor.com, a popular real estate platform, used Flutter to build its mobile app. It offers features like property search, filtering, and alerts.

e) Hamilton

Hamilton is a popular Broadway musical that offers a mobile app built with Flutter. It provides information about the show, behind-the-scenes content, and ticket purchasing.

f) Hookle

Hookle is a social media management app that uses Flutter for its mobile interface. It offers features like post-scheduling, analytics, and cross-platform publishing.

g) Coach Yourself

Coach Yourself is a mental wellness app that uses Flutter for its mobile interface. It offers features like mood tracking, stress management, and personalized coaching.

23. What is a Provider in Flutter?

A Provider is a design pattern that is used to manage the state of an application. It is a way to pass data between widgets in the widget tree without having to manually pass it down through the hierarchy.

At its core, a Provider is a simple object that holds a piece of data. The data can be anything from a simple boolean value to a complex object. When a widget needs access to the data, it can use the Provider to retrieve it.

The Provider design pattern is based on the concept of dependency injection, which is a way of providing objects with the dependencies they need to function. In the context of Flutter, a Provider is used to provide widgets with the data they need to render themselves.

Flutter provides a built-in Provider package that makes it easy to use the Provider pattern in your application. The package provides several classes and utilities that make it easy to manage and update your app’s state.

24. What are the benefits of a Provider in Flutter?

Using a Provider in your application has several benefits, including:

a) Simplified state management 

A Provider can simplify the way you manage the state in your application by providing a centralized location for your app’s data.

b) Improved performance

By using a Provider, you can reduce the number of rebuilds that are required when data changes, which can improve the performance of your application.

c) Easier to maintain

A Provider can make your code easier to maintain by reducing the amount of boilerplate code that you need to write.

25. How can you improve the performance of your Flutter application?

Here are some tips to improve the performance of your Flutter application:

a) Use const constructors

Use const constructors for widgets wherever possible. This reduces the amount of work that Flutter has to do when building the widget tree and can improve performance.

b) Minimize widget rebuilds

Avoid unnecessary widget rebuilds by using the shouldRebuild method in the Provider package or the shouldUpdate method in the State class. This can help to reduce the amount of work that Flutter has to do when rebuilding the widget tree.

c) Use the appropriate widget for the job

Choose the appropriate widget for the job based on the requirements of your UI. For example, use the Text widget for simple text, and the RichText widget for more complex text with inline styling.

d) Optimize images

Optimize your images by compressing them and reducing their size. You can also use the CachedNetworkImage package to cache network images and reduce the amount of data that is transferred over the network.

e) Use the ListView.builder constructor

Use the ListView.builder constructor instead of the ListView constructor whenever possible. This constructor only builds the widgets that are currently visible on the screen, which can improve performance.

f) Use the appropriate build mode

Use the appropriate build mode for your application. For example, use the release build mode when building the final version of your application to reduce the size of your app and improve performance.

g) Use async and await

Use async and await to perform asynchronous operations in your application. This can help to keep the UI responsive and improve the perceived performance of your application.

Such topics are commonly asked when you apply for a job. Hence, be prepared for this type of Flutter interview questions for 2 years experience. It’s also relevant for senior developers as well. 

26. What is the difference between setState() and Provider in Flutter?

These are the main differences between Provider and setState():

27. How can you persist data in a Flutter application?

There are several ways to persist data in a Flutter application:

a) SharedPreferences: 

This is a key-value store that can be used to store small amounts of data such as user preferences. SharedPreferences can be accessed across different screens and can be useful for storing simple data.

b) SQLite: 

SQLite is a relational database management system that can be used to store and retrieve complex data in a Flutter application. It is a popular choice for persisting data in mobile applications because it is lightweight and provides a fast and reliable way to store data.

c) Files:

Files can be used to store data in a structured format such as JSON or CSV. This is useful when you need to store larger amounts of data or when you need to create custom file formats.

d) Cloud storage: 

You can use cloud storage services such as Firebase Cloud Firestore or Google Cloud Storage to store and retrieve data in a Flutter application. This is useful when you need to share data between multiple users or devices.

e) Hive: 

Hive is a lightweight and fast NoSQL database that can be used to persist data in a Flutter application. It is optimized for mobile devices and provides a simple and easy-to-use API for storing and retrieving data.

f) ObjectBox: 

ObjectBox is a high-performance NoSQL database that can be used to persist data in a Flutter application. It is optimized for mobile devices and provides a simple and easy-to-use API for storing and retrieving data.

The choice of the persistence mechanism depends on the specific requirements of your application. For simple data, SharedPreferences or files may be sufficient, while more complex data may require the use of a relational or NoSQL database.

While preparing for Flutter developer interview questions and answers, make sure to know answer to these concepts. 

28. What is SafeArea widget in Flutter and its uses?

The SafeArea widget in Flutter is a container that insets its child by the safe area of the device. The safe area is the area of the device’s screen that is guaranteed to be visible and not obscured by the device’s status bar, navigation bar, or other system UI elements.

This widget is typically used to ensure that the content of an app is not hidden by these system UI elements. For example, on devices with a notch or a camera cutout, the SafeArea widget can be used to ensure that the content of the app is not hidden behind the notch.

To use the SafeArea widget, you simply wrap your content widget inside it. The SafeArea widget will then ensure that the content is inset by the safe area of the device.

Example:

Here is an example of how to use the SafeArea widget in Flutter:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {

  @override

  Widget build(BuildContext context) {

    return MaterialApp(

      home: SafeArea(

        child: Scaffold(

          appBar: AppBar(

            title: Text('Safe Area Example'),

          ),

          body: Center(

            child: Text('This is an example of using the SafeArea widget.'),

          ),

        ),

      ),

    );

  }

}

In this example, the SafeArea widget is used to wrap the Scaffold widget, ensuring that the content of the app is inset by the safe area of the device.

29. How can you handle user input in Flutter?

The user input can be handled in several ways depending on the type of input and the desired behavior. Here are some of the most common ways:

a) Text input: 

To handle text input from the user, you can use the TextFormField or TextField widgets. 

These widgets provide a text input field that the user can type into. To handle the input, you can use the onChanged or onSubmitted callback to get the text entered by the user and update your app’s state accordingly.

b) Button press: 

To handle button press events, you can use the RaisedButton, FlatButton, or IconButton widgets. 

These widgets provide a button that the user can tap to trigger an action in your app. To handle the button press event, you can use the onPressed callback to execute the desired action.

c) Gesture detection: 

To handle gestures such as taps, swipes, or pinches, you can use the GestureDetector widget. 

This widget allows you to detect a wide range of gestures and trigger an action in response. To handle the gesture, you can use the onTap, onDoubleTap, onLongPress, or other callback functions provided by the GestureDetector widget.

d) Slider or switch: 

To handle input from sliders or switches, you can use the Slider or Switch widgets. 

These widgets provide a slider or switch that the user can use to select a value or toggle a setting. To handle the input, you can use the onChanged callback to update your app’s state with the new value or setting.

e) Dropdown list: 

To handle input from a dropdown list, you can use the DropdownButton widget. 

This widget provides a dropdown list that the user can select an item from. To handle the selection, you can use the onChanged callback to update your app’s state with the selected item.

30. How can you use animations in Flutter?

Flutter provides several ways to create animations in your app. Here are some of the best ways:

a) AnimationController: 

You can use the AnimationController class to control the duration, direction, and intensity of the animation. You can define the animation values and specify the duration, and the AnimationController will update the values over time.

b) Tween: 

You can use the Tween class to define the range of values that the animation will interpolate between. The Tween class takes a begin and an end value and returns a value between the two values based on the animation’s progress.

c) AnimatedWidget: 

You can use the AnimatedWidget class to create a widget that automatically rebuilds itself when the animation updates. This allows you to create complex animations without having to manually update the widget’s state.

d) AnimatedBuilder: 

You can use the AnimatedBuilder class to build a widget tree that animates when the animation updates. This allows you to build complex animations with multiple widgets and customize the animation’s behavior.

e) Hero animations: 

You can use Hero animations to create a smooth transition between two screens. You can use the Hero widget to wrap the widget that you want to transition and specify a unique tag. When the widget is clicked, it will smoothly transition to the same widget on the new screen.

f) Implicit animations: 

You can use Implicit animations to create simple animations that are triggered by a change in the widget’s properties. You can use the AnimatedOpacity, AnimatedPadding, and AnimatedContainer classes to animate changes in opacity, padding, and size, respectively.

When you have some experience, you must expect such Flutter interview questions for 3 years of experience. 

31. What is the difference between main() and runApp() in Flutter?

The main() and runApp() are both important functions that are used to bootstrap and run a Flutter application. 

Here is a comparison table that explains the differences between the two:

The main() function is the entry point of a Flutter app and is required in every Flutter app. It sets up the Flutter framework and initializes the app. It can also take command line arguments and be used to initialize external dependencies. The main() function must return void.

The runApp() function, on the other hand, is optional and is used to start the app’s widget tree. It takes a widget as an argument, which becomes the root of the widget tree. 

The widget tree is the hierarchical structure of widgets that make up the app’s user interface. The runApp() function also initializes the app’s default route and sets up the app’s top-level widget tree. The runApp() function returns void.

32. Flutter Technical Interview Questions (Coding)

To truly test your skills, Flutter coding interview questions are often used during the process. Our guide provides a list of commonly asked technical and practical questions with their answers, giving you the opportunity to practice and refine your coding skills before the big day.

33. Write a Flutter widget to display a list of items fetched from an API endpoint.

Here is how you can display a list in Flutter fetched from API endpoint:

Program:

import 'dart:convert';

import 'package:flutter/material.dart';

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

class MyListWidget extends StatefulWidget {

  @override

  _MyListWidgetState createState() => _MyListWidgetState();

}

class _MyListWidgetState extends State {

  List items = [];

  @override

  void initState() {

    super.initState();

    _fetchItems();

  }

  Future _fetchItems() async {

    final response = await http.get(Uri.parse('https://example.com/items'));

    if (response.statusCode == 200) {

      setState(() {

        items = jsonDecode(response.body);

      });

    } else {

      throw Exception('Failed to fetch items');

    }

  }

  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBar: AppBar(

        title: Text('My List'),

      ),

      body: ListView.builder(

        itemCount: items.length,

        itemBuilder: (context, index) {

          final item = items[index];

          return ListTile(

            title: Text(item['title']),

            subtitle: Text(item['subtitle']),

            onTap: () {

              // do something when the item is tapped

            },

          );

        },

      ),

    );

  }

}

Explanation:

Here, we define a MyListWidget class that extends StatefulWidget. The widget’s state includes a List variable called items, which will store the items fetched from the API endpoint.

When the widget is created, the initState method is called, which in turn calls _fetchItems. This method sends an HTTP GET request to the API endpoint using the http package and updates the widget’s state with the fetched items.

The widget’s build method returns a Scaffold with an AppBar and a ListView.builder. The ListView.builder is used to display the items in a scrollable list. The itemCount property is set to the length of the items list, and the itemBuilder function is called for each item in the list. 

The ListTile widget is used to display each item’s title and subtitle. You can customize this widget according to your needs.

Finally, you can add any functionality you like when the user taps an item by defining it in the onTap property of the ListTile.

Suggested Reading: Java 8 Interview Questions and Answers 

34. Write a Flutter widget that displays a form for a user to input data and sends it to an API endpoint.

Program:

import 'dart:convert';

import 'package:flutter/material.dart';

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

class MyFormWidget extends StatefulWidget {

  @override

  _MyFormWidgetState createState() => _MyFormWidgetState();

}

class _MyFormWidgetState extends State {

  final _formKey = GlobalKey();

  String _name = '';

  String _email = '';

  Future _submitForm() async {

    if (_formKey.currentState!.validate()) {

      _formKey.currentState!.save();

      final response = await http.post(Uri.parse('https://example.com/submit-form'),

          body: {'name': _name, 'email': _email});

      if (response.statusCode == 200) {

        // handle success

      } else {

        throw Exception('Failed to submit form');

      }

    }

  }

  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBa