Top Flutter Interview Questions | Top Dart Interview Questions | Flutter Job Interview Questions | Common Flutter interview questions
What is state Management in Flutter ?
Answer: State management in Flutter refers to the process of managing the state or data of an application and ensuring that the user interface (UI) updates in response to state changes. In flutter there are various state management such as Getx, Provider, BLoC, RiverPod etc
Difference between Flutter and Dart ?
Answer: Flutter is an open-source UI software development toolkit created by Google. It is used to develop applications for Android, iOS, Linux, macOS, Windows, Google Fuchsia, and the web from a single codebase.
Dart is the programming language used to code Flutter applications. Dart is also developed by Google and is optimized for building fast, cross-platform mobile, desktop, server, and web applications.
Difference between StatelessWidget and StatefulWidget?
Answer:
- StatelessWidget: A widget that does not require mutable state. Once created, it cannot change.
- StatefulWidget: A widget that has a mutable state. It can be redrawn multiple times while the app is in use.
Explain the lifecycle of a StatefulWidget.
Answer: The lifecycle methods are:
- createState(): Called when the framework is instructed to create a StatefulWidget.
- initState(): Called when the state object is created.
- didChangeDependencies(): Called when the state object’s dependencies change.
- build(): Called when the state object’s build method is called.
- didUpdateWidget(): Called when the widget is rebuilt.
- setState(): Called to update the state of the widget.
- deactivate(): Called when the state object is removed from the tree temporarily.
- dispose(): Called when the state object is permanently removed from the tree.
Difference between deactivate and dispose in flutter ?
- deactivate(): Called when the state object is removed from the tree temporarily.
- dispose(): Called when the state object is permanently removed from the tree.
How do you update the state of a StatefulWidget?
Answer: By calling the setState() method. This method triggers the build method to redraw the widget with the updated state.
What is a Navigator in Flutter?
Answer: The Navigator manages a stack of widgets and allows for navigation between them. It provides methods for transitioning between routes (screens).
What is a route in Flutter?
Answer: A Route is an abstraction for a “screen” or “page” in a Flutter app. Routes can be managed by a Navigator.
What is the difference between hot reload and hot restart?
Answer:
- Hot Reload: Injects changes into the running app, keeping the app state intact.
- Hot Restart: Restarts the app and does not preserve the state.
What is a Future in Dart?
Answer: A Future represents a potential value or error that will be available at some time in the future. It is used for asynchronous operations.
How do you handle asynchronous operations in Dart?
Answer: Using async and await keywords. Example:
Future<void> fetchData() async {
var data = await someAsyncFunction();
// Handle data
}
What is a Stream in Dart?
Answer: A Stream is a sequence of asynchronous events. It provides a way to listen to a series of data over time.
How do you listen to a Stream in Flutter?
Answer: Using a StreamBuilder widget or the listen method on a Stream.
What is a Provider in Flutter?
Answer: Provider is a state management library that makes it easier to manage and access state across the widget tree.
How do you use Provider for state management?
Answer:
- Add the provider package to your pubspec.yaml.
- Wrap your widget tree in a
ProviderorMultiProvider. - Use
ConsumerorProvider.ofto access the state.
What is the difference between Consumer and Provider.of?
Answer:
- Consumer: Rebuilds only the part of the widget tree it wraps when the provided object changes.
- Provider.of: Reads the provided object but does not listen for changes unless specified.
What is a ChangeNotifier in Flutter?
Answer: A ChangeNotifier is a class that provides change notifications to its listeners. It is often used with Provider for state management.
How do you optimize the performance of a Flutter app?
Answer:
- Minimize the number of widgets created.
- Use
constconstructors where possible. - Avoid using expensive operations in the build method.
How do you manage dependencies in Flutter?
Answer: Dependencies are managed in the pubspec.yaml file. You add the package name and version, and then run flutter pub get to install it.
What is a Sliver in Flutter?
Answer: A Sliver is a portion of a scrollable area. Slivers are used to create custom scroll effects and are a key part of the CustomScrollView widget.
What are keys in Flutter and why are they important?
Answer: Keys are used to preserve the state of widgets across widget tree rebuilds. They help Flutter distinguish between widgets and their states.
What is the difference between RunApp and MaterialApp?
Answer:
- runApp: Initializes the given widget as the root of the widget tree.
- MaterialApp: A convenience widget that wraps several widgets commonly required for a material design application.
What is the use of SafeArea in Flutter?
Answer: SafeArea is a widget that ensures its child is not obscured by system UI elements like the status bar or notch.
How do you persist data in a Flutter app?
Answer: To persist data in a Flutter app, you can any options such as shared preferences, SQLite databases,Hive, or file storage.
Lifecycle of Stateful Widget:
The lifecycle of a StatefulWidget in Flutter:
- createState: Called when the
StatefulWidgetis first created. It returns an instance of the associatedStateclass. - initState: Called once when the
Stateobject is created. It is used for one-time initialization. - didChangeDependencies: Called when the state object’s dependencies change.
- build: Called whenever the widget needs to be rendered. It can be called multiple times, such as when the widget’s state changes.
- setState: Triggers a rebuild by calling the
buildmethod. - didUpdateWidget: Called when the widget configuration changes.
- deactivate: Called when the widget is removed from the widget tree but might be reinserted before the current frame ends.
- dispose: Called when the
Stateobject is permanently removed. This is where you should clean up resources.
This lifecycle allows for efficient and responsive UI updates in Flutter applications.
What is didChangeDependencies in Flutter ?
The didChangeDependencies method is called when the dependencies of the State object change. This can occur when an InheritedWidget that the State depends on changes.
Example:
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
void didChangeDependencies() {
super.didChangeDependencies();
print("Dependencies changed");
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('didChangeDependencies Example'),
),
body: Center(
child: Text('Hello, Flutter!'),
),
);
}
}
Difference between initState and didChangeDependencies ?
Difference between Container and SizedBox ?
Difference between runApp and main in Flutter ?
runApp() is the entry point for starting the Flutter application and main() is entry point of a Dart program
