1. What is Flutter?
Flutter is an open-source UI software development toolkit created by Google. It is used to develop cross-platform applications for mobile, web, and desktop using a single codebase.
2. Explain the key features of Flutter.
- Hot Reload
- Widgets
- Cross-platform development
- Expressive UI
- Native performance
3. What is the primary programming language used in Flutter?
Dart is the primary programming language used in Flutter.
4. Explain the concept of "Hot Reload" in Flutter.
Hot Reload is a feature in Flutter that allows developers to instantly see the effects of code changes without restarting the entire application. It helps in speeding up the development process.
5. What are Widgets in Flutter?
Widgets are the basic building blocks of a Flutter application. Everything in Flutter, including the application itself, is a widget. Widgets can be either stateful or stateless.
6. Differentiate between Stateful and Stateless Widgets.
- Stateless Widgets: These widgets are immutable and cannot change over time.
- Stateful Widgets: These widgets can change their state during the runtime.
7. Explain the Flutter tree structure.
The Flutter tree structure represents the hierarchy of widgets in a Flutter application. It starts with the root widget and branches out to child widgets.
8. What is the pubspec.yaml file in Flutter?
pubspec.yaml is a configuration file in Flutter used to define the project's dependencies, assets, and other settings. It also contains metadata about the project.
9. How do you perform navigation in Flutter?
Navigation in Flutter can be achieved using the Navigator class. The push and pop methods are commonly used for navigating between different screens.
10. What is the purpose of the setState method?
The setState method is used to trigger a rebuild of the widget tree in Flutter. When the state of a stateful widget changes, setState is called to update the UI.
11. Explain the concept of the Flutter widget lifecycle.
Widgets in Flutter go through various lifecycle stages, including create, initState, build, didUpdateWidget, and dispose. Understanding these stages helps manage the state of the widgets effectively.
12. What is the purpose of the BuildContext?
The BuildContext is a handle to the location of a widget in the widget tree. It is used to find the nearest instance of a widget and to rebuild the widget tree.
13. How does Flutter achieve high performance?
Flutter achieves high performance by compiling the Dart code to native ARM code and using a graphics engine called Skia for rendering, resulting in native-like performance.
14. Explain the concept of Flutter packages.
Flutter packages are collections of Dart code and assets that provide a certain functionality. They can be easily integrated into a Flutter project to add features and save development time.
15. What is the purpose of the async and await keywords in Dart?
async and await are used to handle asynchronous programming in Dart. async is used to mark a function as asynchronous, and await is used to pause the execution until the awaited operation completes.
16. What is the difference between final and const in Dart?
final: The value of afinalvariable can be set only once and is evaluated at runtime.const: The value of aconstvariable is known at compile-time and cannot be changed.
17. How can you integrate external packages in Flutter?
External packages can be integrated into a Flutter project by adding them to the pubspec.yaml file under the dependencies section.
18. Explain the purpose of the ListView widget.
ListView is a scrollable list of widgets in Flutter, allowing the user to scroll through a large number of children in a single column or row.
19. What is the purpose of the Future class in Dart?
The Future class in Dart is used to represent a value or error that will be available at some time in the future. It is commonly used for asynchronous programming.
20. How do you handle user input in Flutter?
User input in Flutter is handled using widgets like TextField, GestureDetector, and by listening to events such as onPressed or onChanged.
21. What is a Flutter package and how is it structured?
A Flutter package is a collection of Dart files, assets, and a pubspec.yaml file. It can include reusable code, resources, and configurations.
22. Explain the purpose of the InheritedWidget.
InheritedWidget is a special kind of widget in Flutter that allows data to be passed down the widget tree to its descendants. It helps in efficiently managing and sharing state.
23. How do you handle different screen sizes in Flutter?
Flutter provides a responsive UI by using widgets like MediaQuery and LayoutBuilder. Additionally, the Expanded and Flexible widgets help in creating flexible layouts.
24. What is the purpose of the Hero widget?
The Hero widget in Flutter is used to create hero animations, which smoothly transition a widget from one screen to another. It is often used for a visually appealing user experience.
25. Explain the purpose of the Cupertino widget in Flutter.
The Cupertino widget is part of the Flutter framework and provides iOS-style design elements. It allows developers to create apps that have a native iOS look and feel.
26. How do you implement a custom font in Flutter?
To use a custom font in Flutter, you need to add the font file to the project and define it in the pubspec.yaml file. After that, you can use the font in the TextStyle of a text widget.
27. What is the purpose of the Flutter Doctor command?
flutter doctor is a command-line tool that helps diagnose and solve common issues with Flutter development. It checks the system for dependencies and provides guidance on how to set up a development environment.
28. How do you handle platform-specific code in Flutter?
Platform-specific code in Flutter can be handled using the Platform class and conditional statements. Additionally, Flutter provides the Platform Channel for communicating with native code.
29. Explain the concept of "Widget Key" in Flutter.
A widget key in Flutter is an object that associates a widget with a unique identifier. It is used to maintain widget state during rebuilds and to efficiently update the widget tree.
30. What is the purpose of the async* keyword in Dart?
The async* keyword in Dart is used to create asynchronous generators. It allows the production of a sequence of values over time, similar to a stream, in an asynchronous manner.
31. How do you handle state management in Flutter?
State management in Flutter can be handled using built-in mechanisms like setState for simple cases, and for more complex scenarios, external packages like Provider, Riverpod, or Bloc can be used.
32. What is the purpose of the SingleChildScrollView widget?
The SingleChildScrollView widget is used to create a scrollable view
with a single child. It is useful when the content is too large to fit on the screen.
33. How do you perform unit testing in Flutter?
Flutter provides a testing framework for writing unit tests. Tests can be written using the test package or the built-in testing utilities provided by Flutter.
34. Explain the purpose of the RxDart package in Flutter.
RxDart is an extension of Dart's Streams library and provides reactive programming using the ReactiveX (Rx) paradigm. It is commonly used for managing and reacting to asynchronous events in Flutter applications.
35. What is the purpose of the Scaffold widget in Flutter?
The Scaffold widget is a basic skeletal structure in Flutter that provides an app bar, a body, and a floating action button. It serves as the overall layout for a material design app.
36. How do you implement internationalization (i18n) in Flutter?
Internationalization in Flutter can be implemented using the intl package. This package allows you to handle translations, date and number formatting, and other localization features.
37. What is the purpose of the Expanded widget?
The Expanded widget in Flutter is used to make a child of a Row, Column, or Flex widget expand to fill the available space along the main axis.
38. How can you handle errors in Dart?
Errors in Dart can be handled using try-catch blocks. Dart provides Exception and Error classes, and you can create custom exception classes for specific error scenarios.
39. Explain the purpose of the FutureBuilder widget.
The FutureBuilder widget is used to asynchronously build widgets based on the latest snapshot of interaction with a Future. It's commonly used for handling asynchronous operations in a clean and readable way.
40. What is the purpose of the ClipRRect widget?
The ClipRRect widget is used to clip the child widget with rounded corners. It's often used to create rounded corners for images and other elements.
41. How do you implement a custom transition in Flutter?
Custom transitions in Flutter can be implemented using the PageRouteBuilder or by extending the PageRoute class. This allows developers to create unique and visually appealing transitions between screens.
42. What is the purpose of the Spacer widget?
The Spacer widget is used to create flexible space within a Flex or Column or Row layout. It expands to fill the available space along the main axis.
43. How can you add padding to a widget in Flutter?
Padding in Flutter can be added using the Padding widget or by directly using the padding property of widgets like Container, Card, or ListView.
44. Explain the purpose of the DefaultTabController widget.
The DefaultTabController widget is used to coordinate the behavior of a TabBar and a TabBarView. It ensures that the selected tab index is synchronized between the two.
45. How do you implement a custom painter in Flutter?
A custom painter in Flutter can be implemented by extending the CustomPainter class and overriding the paint and shouldRepaint methods. This is commonly used for creating custom shapes and drawings.
46. What is the purpose of the StreamBuilder widget?
The StreamBuilder widget is used to asynchronously build widgets based on the latest snapshot of interaction with a Stream. It's commonly used for handling real-time data and updates.
47. Explain the purpose of the WillPopScope widget.
The WillPopScope widget is used to intercept the back button press on Android or the navigation pop gesture on iOS. It allows you to define custom behavior when the user tries to navigate back.
48. How do you handle form validation in Flutter?
Form validation in Flutter is often handled using the Form widget along with TextFormField widgets. Validators can be provided to ensure that user input meets specific criteria.
49. What is the purpose of the RefreshIndicator widget?
The RefreshIndicator widget is used to implement the "pull-to-refresh" pattern in Flutter. It provides a standard way to refresh the contents of a scrollable view.
50. How can you implement dark mode in a Flutter app?
Dark mode in Flutter can be implemented by defining a theme for both light and dark modes using the ThemeData class. The MediaQuery can then be used to detect the system's brightness preference and apply the appropriate theme.