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Questions and Answers
A StatelessWidget can be declared with two classes.
A StatelessWidget can be declared with two classes.
False
The setState() method is used to refresh changed data in a StatelessWidget.
The setState() method is used to refresh changed data in a StatelessWidget.
False
Everything in Flutter can be considered a widget.
Everything in Flutter can be considered a widget.
True
Widgets in Flutter are immutable declarations of the user interface.
Widgets in Flutter are immutable declarations of the user interface.
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The StatefulWidget class creates an instance of the Stateless class when the widget's configuration changes.
The StatefulWidget class creates an instance of the Stateless class when the widget's configuration changes.
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Flutter is a proprietary UI framework exclusively for Android applications.
Flutter is a proprietary UI framework exclusively for Android applications.
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Dart programming language is compiled using both ahead-of-time and just-in-time methods within Flutter.
Dart programming language is compiled using both ahead-of-time and just-in-time methods within Flutter.
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The Flutter framework relies on the Cumulative rendering engine to display its widgets.
The Flutter framework relies on the Cumulative rendering engine to display its widgets.
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Flutter widgets can only be stateful, while stateless widgets are not supported.
Flutter widgets can only be stateful, while stateless widgets are not supported.
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Flutter applications maintain a widgets and elements tree to manage the rendering process.
Flutter applications maintain a widgets and elements tree to manage the rendering process.
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Flutter uses elements as the configuration to build each widget.
Flutter uses elements as the configuration to build each widget.
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In Flutter, the 'setState' method is used to rebuild the children widgets in a stateful element.
In Flutter, the 'setState' method is used to rebuild the children widgets in a stateful element.
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The 'createState' method is associated with stateless widgets in Flutter.
The 'createState' method is associated with stateless widgets in Flutter.
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Flutter's architecture allows for code reuse across different operating systems.
Flutter's architecture allows for code reuse across different operating systems.
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Each element in the Flutter element tree is independent of its corresponding widget.
Each element in the Flutter element tree is independent of its corresponding widget.
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The Flutter framework distinguishes between stateless and stateful elements.
The Flutter framework distinguishes between stateless and stateful elements.
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Widgets in Flutter are mounted directly onto the screen without any intermediary.
Widgets in Flutter are mounted directly onto the screen without any intermediary.
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The method 'build' is associated with creating elements in Flutter.
The method 'build' is associated with creating elements in Flutter.
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Flutter uses a single tree structure to manage both widgets and elements.
Flutter uses a single tree structure to manage both widgets and elements.
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A stateful element is created using the 'createElement' method alone.
A stateful element is created using the 'createElement' method alone.
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Study Notes
Mobile Applications (Flutter Foundations)
- This presentation, titled "Mobile Applications (Flutter Foundations: Widgets to Architecture)," is chapter 3 of a course taught by Dr. Mohamad Al-Dabbagh.
- The material covers Flutter Framework and Architecture with specific focus on Widgets.
Outline
- Flutter Framework
- Flutter Widgets
- Widget Types
- Widget Lifecycle
- Widgets & Elements Tree
- Flutter Architecture
- Flutter Features
- Some Basic Widgets
Objectives
- Central concepts of widgets
- Differences between stateless and stateful widgets
- Widget Lifecycle
- Widget & Element Tree
- Flutter Architecture components
- Flutter Features
- Common widgets in Flutter
What is a Flutter?
- Google's portable UI framework for building modern, native, and reactive applications for iOS and Android with one codebase.
- Supports Desktop, Web, and embedded devices.
- An open-source project.
- Uses the Skia 2D rendering engine.
- A framework for the Dart programming language.
Flutter Framework (Relationship)
- Dart
- Flutter Framework
- Flutter SDK
Flutter VS Dart
- Dart is the programming language used in Flutter.
- Flutter framework provides utilities and functions for UI elements (widgets).
- Dart codes are compiled to native code for iOS and Android (ahead-of-time and just-in-time).
- Flutter SDK provides tools to build and test applications.
How Flutter Works?
- Flutter API provides a structure.
- UI/Widgets code is used.
- Dart code is used.
- Code compilation to native code for each platform. (Android or iOS).
- Dart code uses the Android NDK and iOS LLVM for compilation, using ARM libraries.
Flutter Widgets
- Flutter uses Dart to create UI.
- UI is built to reflect app state.
- Fast at 60 & 120 frames per second on compatible devices.
- Widgets are used for UI creation.
- Its own rendering engine is used to draw widgets.
Basic Widgets
- Flutter uses widgets to build UI.
- Widgets contain visual elements and logic.
- Dart is object-oriented; everything is an object.
- A widget is a class starting with the "class" keyword.
Widgets Types (Stateless & Stateful Widgets)
-
Stateless Widget: declared with one class, has a single
buildmethod which can be called on creation or when the parent widget changes, and does not manage internal state. -
Stateful Widget: declared with two classes (widget and state), has a
buildmethod alongside methods likeinitState,didChangeDependencies,didUpdateWidget,deactivate,disposeused for managing internal state that can change over time.setState()is used to reflect changes to the state and update UI accordingly.
Widgets & Elements Tree
- The widget tree holds configuration of the UI.
- The element tree represents a piece of UI.
- Render tree is responsible for painting on the screen.
- Flutter uses widgets as configurations for each mounted element.
- Stateless elements use
createElementandbuildmethods.
Flutter Architecture Overview
- Flutter is a cross-platform UI toolkit, that allows for code reuse across platforms (iOS and Android).
- Flutter interfaces directly with underlying platform services.
- The architecture has a framework (Dart), engine (C/C++) and embedder (platform-specific).
Flutter Features
- Hot Reload: Quickly update code on the fly, preserving app state.
- Hot Restart: Rebuilds the widget tree after code changes.
- Full Restart: Restarts the app; recompiles the platform-specific code (longer, and loses app state).
Flutter Code Structure (Main.dart file)
- The
main.dartfile contains the main application logic. - It does not get renamed and is automatically executed by the Flutter framework.
- Does not require arguments.
Basic Widgets (Some Basic Widgets)
- Scaffold: Basic material design, providing APIs for elements.
- AppBar: Horizontal bar at the top of the screen.
- Text: Displays text.
- TextStyle: Controls appearance of text.
- FontWeight: Thickness of text.
- Colors: Material design colors.
- Center: Centers its child.
- Image: For displaying images.
- NetworkImage: Fetches images from URLs.
- AssetImage: Fetches images from the app's assets.
- Column: Arranges widgets vertically.
- Row: Arranges widgets horizontally.
Adding Images to App
- Pubspec file: Every package needs metadata (dependencies).
- Pub Packages: Shared packages with metadata for discovery.
- Assets are added to the
pubspec.yamlfile in a locationassets.
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Description
Explore the foundational concepts of Flutter in this quiz based on Chapter 3 of Dr. Mohamad Al-Dabbagh's course. Dive into the intricacies of widgets, their lifecycle, and the architecture that supports Flutter applications. Test your knowledge and understanding of this powerful framework for building native applications.
