Flutter Fundamentals & Widgets Interview Questions

Flutter is a UI toolkit that offers: 1) Single codebase for multiple platforms (iOS, Android, Web, Desktop), 2) Widget-based development with rich customizable components, 3) Hot Reload for rapid development, 4) Direct compilation to native code without bridge, 5) Built-in Material Design and Cupertino widgets, 6) High performance with Skia rendering engine, 7) Complete development and debugging tools, 8) Strong community and package ecosystem.

Key differences include: 1) StatelessWidget is immutable and cannot change its state after creation, 2) StatefulWidget maintains mutable state with a separate State object, 3) StatelessWidget rebuild only when parent widget changes, 4) StatefulWidget can rebuild when setState() is called, 5) StatelessWidget is more memory efficient, 6) StatefulWidget is used for user interaction and dynamic content, 7) StatelessWidget is used for static content, 8) State persistence across rebuilds in StatefulWidget.

Widget Tree in Flutter: 1) Hierarchical structure of widgets that describes UI, 2) Parent widgets wrap and affect child widgets, 3) Rebuilds efficiently using element tree, 4) Supports inheritance of theme and media query data, 5) Manages state propagation through tree, 6) Implements build context for widget location, 7) Handles widget lifecycle and disposal, 8) Optimizes rendering through RenderObject tree.

Hot Reload: 1) Updates code changes without app restart, 2) Preserves app state during development, 3) Injects updated source code into running Dart VM, 4) Rebuilds widget tree with new code, 5) Cannot update native code or plugin changes, 6) Requires stateful hot reload capable code, 7) May need hot restart for some changes, 8) Maintains constructor state across reloads.

Key layout widgets: 1) Container for styling and positioning, 2) Row and Column for linear layouts, 3) Stack for overlapping elements, 4) Expanded and Flexible for responsive sizing, 5) GridView for grid layouts, 6) ListView for scrollable lists, 7) Wrap for flow layouts, 8) Custom SingleChildScrollView for scrollable content. Usage depends on layout requirements and content organization needs.

BuildContext provides: 1) Location of widget in widget tree, 2) Access to inherited widgets, 3) Theme and MediaQuery data access, 4) Navigation services, 5) State management access, 6) Localization data, 7) Scaffold messenger access, 8) Widget tree traversal capabilities. Essential for accessing widget tree information and services.

Keys are used for: 1) Maintaining widget state across moves in widget tree, 2) Uniquely identifying widgets, 3) Preserving scroll position in lists, 4) Managing widget lifecycle, 5) Handling dynamic widget updates, 6) Implementing list item reordering, 7) Preserving form field states, 8) Optimizing widget rebuilds. Important for widget identity and state preservation.

Widget lifecycle includes: 1) Constructor creation, 2) initState for StatefulWidget initialization, 3) didChangeDependencies for inherited widget changes, 4) build for UI rendering, 5) didUpdateWidget for widget updates, 6) setState for state changes, 7) dispose for cleanup, 8) deactivate for temporary removal. Understanding lifecycle is crucial for proper state management.

InheritedWidget provides: 1) Efficient data sharing down widget tree, 2) Automatic rebuild of dependent widgets, 3) Access to shared data through context, 4) State management capabilities, 5) Theme and MediaQuery implementation, 6) Dependency tracking, 7) Performance optimization, 8) Widget tree scoped data access. Used for efficient data propagation.

Responsive design techniques: 1) Using MediaQuery for screen dimensions, 2) LayoutBuilder for constraints-based layouts, 3) Flexible and Expanded widgets, 4) OrientationBuilder for orientation changes, 5) Responsive grid systems, 6) Adaptive widgets, 7) Custom responsive layouts, 8) Platform-specific adaptations. Essential for cross-device compatibility.

Key differences: 1) Container allows decoration and padding, 2) SizedBox is more lightweight and efficient, 3) Container can have multiple children through child property, 4) SizedBox primarily for dimensional constraints, 5) Container supports margin and alignment, 6) SizedBox for fixed dimensions, 7) Container for styling purposes, 8) SizedBox for space creation.

Gesture handling includes: 1) GestureDetector widget for touch events, 2) InkWell for Material Design ripple effect, 3) Drag and drop support, 4) Multi-touch handling, 5) Custom gesture recognition, 6) Pan and zoom gestures, 7) Tap and long press detection, 8) Gesture arena resolution.

Button types include: 1) ElevatedButton for raised buttons, 2) TextButton for flat buttons, 3) OutlinedButton for outlined style, 4) IconButton for icon-only buttons, 5) FloatingActionButton for floating actions, 6) PopupMenuButton for menus, 7) DropdownButton for selections, 8) Custom button implementations.

Form validation involves: 1) Form widget for form state management, 2) TextFormField for input validation, 3) GlobalKey<FormState> for form control, 4) Custom validators, 5) Form submission handling, 6) Error message display, 7) Real-time validation, 8) Form reset functionality.

Custom widgets are used for: 1) Reusable UI components, 2) Complex widget combinations, 3) Encapsulating business logic, 4) Improving code organization, 5) Maintaining consistent styling, 6) Reducing code duplication, 7) Better testing isolation, 8) Component abstraction.

Flutter is a UI toolkit that offers: 1) Single codebase for multiple platforms (iOS, Android, Web, Desktop), 2) Widget-based development with rich customizable components, 3) Hot Reload for rapid development, 4) Direct compilation to native code without bridge, 5) Built-in Material Design and Cupertino widgets, 6) High performance with Skia rendering engine, 7) Complete development and debugging tools, 8) Strong community and package ecosystem.

Key differences include: 1) StatelessWidget is immutable and cannot change its state after creation, 2) StatefulWidget maintains mutable state with a separate State object, 3) StatelessWidget rebuild only when parent widget changes, 4) StatefulWidget can rebuild when setState() is called, 5) StatelessWidget is more memory efficient, 6) StatefulWidget is used for user interaction and dynamic content, 7) StatelessWidget is used for static content, 8) State persistence across rebuilds in StatefulWidget.

Widget Tree in Flutter: 1) Hierarchical structure of widgets that describes UI, 2) Parent widgets wrap and affect child widgets, 3) Rebuilds efficiently using element tree, 4) Supports inheritance of theme and media query data, 5) Manages state propagation through tree, 6) Implements build context for widget location, 7) Handles widget lifecycle and disposal, 8) Optimizes rendering through RenderObject tree.

Hot Reload: 1) Updates code changes without app restart, 2) Preserves app state during development, 3) Injects updated source code into running Dart VM, 4) Rebuilds widget tree with new code, 5) Cannot update native code or plugin changes, 6) Requires stateful hot reload capable code, 7) May need hot restart for some changes, 8) Maintains constructor state across reloads.

Key layout widgets: 1) Container for styling and positioning, 2) Row and Column for linear layouts, 3) Stack for overlapping elements, 4) Expanded and Flexible for responsive sizing, 5) GridView for grid layouts, 6) ListView for scrollable lists, 7) Wrap for flow layouts, 8) Custom SingleChildScrollView for scrollable content. Usage depends on layout requirements and content organization needs.

BuildContext provides: 1) Location of widget in widget tree, 2) Access to inherited widgets, 3) Theme and MediaQuery data access, 4) Navigation services, 5) State management access, 6) Localization data, 7) Scaffold messenger access, 8) Widget tree traversal capabilities. Essential for accessing widget tree information and services.

Keys are used for: 1) Maintaining widget state across moves in widget tree, 2) Uniquely identifying widgets, 3) Preserving scroll position in lists, 4) Managing widget lifecycle, 5) Handling dynamic widget updates, 6) Implementing list item reordering, 7) Preserving form field states, 8) Optimizing widget rebuilds. Important for widget identity and state preservation.

Widget lifecycle includes: 1) Constructor creation, 2) initState for StatefulWidget initialization, 3) didChangeDependencies for inherited widget changes, 4) build for UI rendering, 5) didUpdateWidget for widget updates, 6) setState for state changes, 7) dispose for cleanup, 8) deactivate for temporary removal. Understanding lifecycle is crucial for proper state management.

InheritedWidget provides: 1) Efficient data sharing down widget tree, 2) Automatic rebuild of dependent widgets, 3) Access to shared data through context, 4) State management capabilities, 5) Theme and MediaQuery implementation, 6) Dependency tracking, 7) Performance optimization, 8) Widget tree scoped data access. Used for efficient data propagation.

Responsive design techniques: 1) Using MediaQuery for screen dimensions, 2) LayoutBuilder for constraints-based layouts, 3) Flexible and Expanded widgets, 4) OrientationBuilder for orientation changes, 5) Responsive grid systems, 6) Adaptive widgets, 7) Custom responsive layouts, 8) Platform-specific adaptations. Essential for cross-device compatibility.

Key differences: 1) Container allows decoration and padding, 2) SizedBox is more lightweight and efficient, 3) Container can have multiple children through child property, 4) SizedBox primarily for dimensional constraints, 5) Container supports margin and alignment, 6) SizedBox for fixed dimensions, 7) Container for styling purposes, 8) SizedBox for space creation.

Gesture handling includes: 1) GestureDetector widget for touch events, 2) InkWell for Material Design ripple effect, 3) Drag and drop support, 4) Multi-touch handling, 5) Custom gesture recognition, 6) Pan and zoom gestures, 7) Tap and long press detection, 8) Gesture arena resolution.

Button types include: 1) ElevatedButton for raised buttons, 2) TextButton for flat buttons, 3) OutlinedButton for outlined style, 4) IconButton for icon-only buttons, 5) FloatingActionButton for floating actions, 6) PopupMenuButton for menus, 7) DropdownButton for selections, 8) Custom button implementations.

Form validation involves: 1) Form widget for form state management, 2) TextFormField for input validation, 3) GlobalKey<FormState> for form control, 4) Custom validators, 5) Form submission handling, 6) Error message display, 7) Real-time validation, 8) Form reset functionality.

Custom widgets are used for: 1) Reusable UI components, 2) Complex widget combinations, 3) Encapsulating business logic, 4) Improving code organization, 5) Maintaining consistent styling, 6) Reducing code duplication, 7) Better testing isolation, 8) Component abstraction.

Key differences include: 1) const is compile-time constant, final is runtime constant, 2) const requires all values to be known at compile time, 3) final can be set once at runtime, 4) const objects are canonicalized, 5) const constructors create immutable objects, 6) final allows for lazy initialization, 7) const improves performance for widgets, 8) final is used for runtime-dependent values.

Differences include: 1) SafeArea adjusts for system intrusions, 2) Padding adds space around content, 3) SafeArea handles notches and system bars, 4) Padding is for explicit spacing control, 5) SafeArea uses MediaQuery data, 6) Padding uses EdgeInsets, 7) SafeArea for device-specific adjustments, 8) Padding for layout spacing.

Flex and Expanded features: 1) Flex determines axis of layout, 2) Expanded fills available space, 3) flex factor for space distribution, 4) Flexible vs Expanded behavior, 5) Cross-axis alignment control, 6) Main-axis size behavior, 7) Nested flex layouts, 8) Space distribution algorithms.

Slivers provide: 1) Custom scrolling effects, 2) Efficient scrollable layouts, 3) AppBar animations, 4) Lazy loading of content, 5) Custom scroll physics, 6) Persistent headers, 7) Grid and list layouts, 8) Performance optimization for scrolling. Used for complex scrolling behaviors.

Asset management includes: 1) pubspec.yaml configuration, 2) Asset bundling process, 3) Resolution-aware images, 4) Font integration, 5) Asset variants handling, 6) Package asset access, 7) Asset loading optimization, 8) Asset organization strategies.

GlobalKey purposes: 1) Accessing widget state across tree, 2) Unique widget identification, 3) Form validation control, 4) Navigator state access, 5) Scaffold manipulation, 6) Animation control, 7) Widget reference maintenance, 8) Cross-tree communication.

Keyboard handling includes: 1) FocusNode management, 2) TextInput configuration, 3) Keyboard type selection, 4) Keyboard visibility detection, 5) Input action handling, 6) Focus traversal, 7) Keyboard dismissal, 8) Custom keyboard layouts.

ScrollView types include: 1) ListView for linear scrolling, 2) GridView for grid layouts, 3) SingleChildScrollView for single child, 4) CustomScrollView for slivers, 5) PageView for swipeable pages, 6) NestedScrollView for nested scrolling, 7) ScrollController usage, 8) Scroll physics customization.

Theming implementation: 1) ThemeData configuration, 2) Theme inheritance, 3) Custom theme creation, 4) Dark mode support, 5) Dynamic theme switching, 6) Theme extension, 7) Platform-specific theming, 8) Theme data persistence.

Stack and Positioned: 1) Stack allows overlapping children, 2) Positioned controls child position, 3) Stack alignment properties, 4) Positioned absolute positioning, 5) Stack fit behavior, 6) Z-index ordering, 7) Overflow handling, 8) Size constraints management.

Error handling includes: 1) ErrorWidget customization, 2) BuildContext error handling, 3) Error callback implementation, 4) Widget error recovery, 5) Error reporting, 6) Debug error display, 7) Production error handling, 8) Error boundary widgets.

Widget composition practices: 1) Single responsibility principle, 2) Proper widget extraction, 3) State management consideration, 4) Performance optimization, 5) Code reusability, 6) Proper inheritance use, 7) Component interface design, 8) Widget testing strategy.

Localization implementation: 1) MaterialApp localization delegates, 2) Locale resolution, 3) Asset localization, 4) String internationalization, 5) RTL support, 6) Currency formatting, 7) Date/time localization, 8) Custom localizations.

Visibility approaches: 1) Visibility widget usage, 2) Opacity widget control, 3) Offstage widget, 4) Conditional rendering, 5) AnimatedOpacity transitions, 6) Layout builder conditions, 7) Stack positioning, 8) Custom visibility controllers.

Disposal and cleanup: 1) dispose() method implementation, 2) Controller cleanup, 3) Stream subscription cancellation, 4) Animation controller disposal, 5) Timer cancellation, 6) Resource release, 7) Memory leak prevention, 8) State cleanup patterns.