Top Flutter Interview Questions and Answers

Here are top Flutter interview questions,

1. What is Flutter?

Flutter is an open-source UI framework developed by Google for building natively compiled applications for mobile, web, and desktop from a single codebase.

 

2. What programming language is used in Flutter?

Flutter uses Dart as its primary programming language. Dart is an object-oriented language with features that help build modern, reactive UIs.

 

3. What is a widget in Flutter?

A widget is a basic building block of the Flutter UI. Everything in Flutter is a widget, including buttons, text, images, layouts, etc. Widgets can be combined to create complex user interfaces.

 

4. What is the difference between StatelessWidget and StatefulWidget in Flutter?

StatelessWidget is a widget that does not have any mutable state. It is immutable and cannot change over time. StatefulWidget, on the other hand, can maintain state and update its UI based on that state.

 

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

The pubspec.yaml file is used to define the dependencies and metadata for a Flutter project. It specifies the Flutter SDK version, package dependencies, assets, and other configuration details.

 

6. How do you navigate between screens in Flutter?

In Flutter, you can navigate between screens using the Navigator class. You can push a new screen onto the stack using the `Navigator.push()` method, and pop the current screen using `Navigator.pop()`.

 

7. What is a StatelessWidget in Flutter?

StatelessWidget is a widget that represents part of the user interface. It does not have any mutable state and is typically used for static content or UI elements that do not change over time.

 

8. What is a StatefulWidget in Flutter?

StatefulWidget is a widget that can hold mutable state. It allows you to update its UI dynamically based on changes in the state. It is used when the UI needs to respond to user interactions or external events.

 

9. What is a Future in Flutter?

A Future represents a value or error that may not be available yet. It is used to perform asynchronous operations and handle the result when it becomes available.

 

10. How do you handle state in Flutter?

In Flutter, you can handle state by using StatefulWidget. The state is maintained in a separate State class associated with the StatefulWidget. Changes to the state trigger a rebuild of the UI.

 

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

Hot reload allows you to update the code and see the changes immediately in the running app without losing the app's state. Hot restart restarts the app from scratch, losing the current state but applying code changes.

 

12. What are keys in Flutter?

Keys are used to uniquely identify widgets in Flutter. They help Flutter efficiently update and manage the state of widgets when the UI changes.

 

13. What is the difference between `setState()` and `StreamBuilder` in Flutter?

'setState()` is used to update the state of a widget and trigger a rebuild of the UI. It is typically used for small changes within a single widget. `StreamBuilder` is used to reactively update the UI based on asynchronous data streams.

 

14. What is the purpose of the main() function in Flutter?

The main() function in Flutter is the entry point of the application. It initializes the Flutter framework, runs the app, and sets up the initial UI.

 

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

The build() method is responsible for creating the widget's UI based on the current state and props. It is called whenever the widget needs to be built or rebuilt.

 

16. What is a StatelessWidget in Flutter?

StatelessWidget is a widget that represents part of the user interface. It does not have any mutable state and is typically used for static content or UI elements that do not change over time.

 

17. How do you handle user input in Flutter?

To handle user input in Flutter, you can use various gesture recognizers like `GestureDetector` or specific widgets like `TextField` for text input. You can listen for events and update the UI or trigger actions accordingly.

 

18. What is the purpose of the `async` and `await` keywords in Flutter?

The `async` and `await` keywords are used to work with asynchronous code in a more synchronous manner. `async` is used to define an asynchronous function, and `await` is used to pause the function's execution until a `Future` completes.

 

19. How do you handle platform-specific code in Flutter?

Flutter provides a mechanism called platform channels to interact with platform-specific code. You can use `MethodChannel` or `EventChannel` to communicate with native code and access platform-specific features.

 

20. What is Flutter's widget tree?

The widget tree in Flutter represents the hierarchy of widgets that make up the user interface. Each widget can have child widgets, forming a tree-like structure. The framework traverses this tree to build and update the UI efficiently.

Above are few top Flutter interview questions. Remember to prepare and expand on these answers.

Good luck with your interview!  👍