Jan 17, 2023 iOS

Flutter interview questions and answers

1.What is Flutter and what are its advantages?

Flutter is an open-source mobile app development SDK created by Google. It uses the Dart programming language and allows developers to build high-performance, cross-platform applications for iOS and Android with a single codebase. Some advantages of using Flutter include fast development, hot reload feature, customizable widgets, and excellent documentation.

2.What is the difference between Stateful and Stateless widgets in Flutter?

Stateful widgets maintain state that can change over time, such as user input, while Stateless widgets do not. Stateless widgets are immutable and their properties cannot be changed once they are created. Stateful widgets are more complex but allow for more dynamic user interfaces.

3.What is a Stream in Flutter?

A Stream is a sequence of asynchronous events that can be processed in a reactive way. Streams are used in Flutter to handle asynchronous data such as user input, network requests, and database queries.

4.What is a Future in Flutter?

A Future represents a value that may not be available yet. Futures are used in Flutter to handle asynchronous operations such as network requests and database queries. Once the value is available, the Future can be completed and the result can be accessed.

5.What is the purpose of the Widget build() method in Flutter?

The build() method is used to create and return the widget hierarchy for a given widget tree. It is called by the Flutter framework when the widget needs to be rebuilt. The build() method should be pure and not have any side effects. It should only create a new widget hierarchy based on the current widget properties.

6.What is the difference between Navigator.push() and Navigator.pushReplacement() in Flutter?

Navigator.push() adds a new screen to the top of the navigation stack, while Navigator.pushReplacement() replaces the current screen with a new one. Navigator.pushReplacement() is useful for implementing login screens or other screens that should not be accessible once the user has already navigated past them.

7.What is a GlobalKey in Flutter?

A GlobalKey is a unique identifier that can be used to reference a widget from anywhere in the widget tree. GlobalKeys are useful for accessing the state of a widget or for manipulating a widget from outside its parent.

8.What is the purpose of the setState() method in Flutter?

The setState() method is used to notify the framework that the state of a widget has changed and that it needs to be rebuilt. When setState() is called, the build() method is called again with the updated widget properties.

9.How can you handle user input in Flutter?

You can handle user input in Flutter using a variety of widgets such as TextField, Checkbox, Radio, and Switch. These widgets have callback functions that are called when the user interacts with them, allowing you to update the state of your application.

10.How can you handle asynchronous data in Flutter?

You can handle asynchronous data in Flutter using Futures, Streams, and the async/await keywords. Futures represent values that may not be available yet, while Streams represent sequences of asynchronous events. The async/await keywords make it easier to write asynchronous code that looks synchronous.

11.What are the advantages of Flutter over other mobile app development frameworks?

Flutter has several advantages over other mobile app development frameworks. Some of the significant advantages are:

  • Flutter provides hot-reload feature, which makes it easier to test and fix bugs in real-time.
  • It offers a single codebase for multiple platforms, saving development time and reducing costs.
  • Flutter has a large and active community, providing excellent support and regular updates.
  • It comes with a rich set of pre-built widgets, which allows for faster development of UI/UX.
  • It has better performance and provides smoother animations compared to other frameworks.

12.How does Flutter handle different screen sizes?

Flutter provides a widget called MediaQuery, which helps to adapt the layout of the app based on the device screen size. It allows developers to access the current device screen size and other device-specific metrics like the device’s orientation, pixel density, and aspect ratio.

13.What is a Navigator widget in Flutter?

The Navigator widget is a widget that manages a stack of pages or screens in the app. It provides navigation functionalities like pushing a new screen onto the stack, popping a screen from the stack, and replacing the current screen with a new one.

14.What is a Flutter widget tree?

A Flutter widget tree is a hierarchical structure of widgets that represents the UI of the app. Each widget in the tree has a specific role and is responsible for rendering a particular part of the UI. Widgets can be nested inside other widgets to create complex UI elements.

15.What is the purpose of the main.dart file in Flutter?

The main.dart file is the entry point for a Flutter app. It contains the main() function, which is the starting point for the app. The main() function creates and runs an instance of the app’s root widget.

16.How do you handle asynchronous operations in Flutter?

Flutter provides a Future class that represents a value or error that will be available at some point in the future. To handle asynchronous operations, developers can use the async/await keywords to create asynchronous functions that can perform operations like network requests, database queries, and file I/O.

17.What is a MaterialApp in Flutter?

MaterialApp is a pre-built widget in Flutter that provides a basic structure for material design apps. It includes pre-built widgets for common UI elements such as buttons, text fields, and dialogs, as well as navigation and theming.

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

Hot reload allows developers to make changes to the code and see the changes in the app immediately without losing the app’s state. Hot restart, on the other hand, restarts the app from scratch, which means that the app’s state is lost.

19.What is the purpose of the pubspec.yaml file in a Flutter app?

The pubspec.yaml file is a configuration file in a Flutter app that specifies the dependencies, assets, and metadata of the app. It is used by the Flutter tool to download the required dependencies and assets.

20.What is an InheritedWidget in Flutter?

An InheritedWidget is a widget that passes data down the widget tree to its descendants. It is used when data needs to be shared across multiple widgets in the widget tree.

21.What is the purpose of initState() in Flutter?

The initState() method is called when a StatefulWidget is inserted into the widget tree for the first time. It is used to initialize the mutable state of the widget.