Flutter Framework

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Questions and Answers

What is the purpose of the 'test' package in Flutter?

writing tests (unit and integration), grouping tests, assertions, and running tests.

What does the 'flutter_test' package offer for testing Flutter widgets?

It extends the test package with functionalities specifically for testing Flutter widgets. It allows pumping widgets, interacting with them, and verifying their behavior and appearance.

How does the 'mockito' package aid in testing Flutter applications?

It helps in creating mock objects for dependency injection in unit tests, isolating code under test, and controlling the behavior of dependencies.

What is Flutter?

Flutter is a highly adaptable and robust framework designed for crafting applications that work seamlessly across multiple platforms. Signup and view all the answers

Which programming language is used for the embedder layer in Flutter?

Objective-C Signup and view all the answers

Stateful widgets are used to build UI elements that need to be updated upon user interaction.

True Signup and view all the answers

Form widget in Flutter is typically used for designing ____________.

login/signup page Signup and view all the answers

Match the following layout widgets with their functions:

Container = Adds margins, borders, padding, background color, etc. Row = Lays widgets horizontally Column = Lays widgets vertically Stack = Overlaps widgets on top of each other Signup and view all the answers

What is the main difference between responsiveness and adaptiveness in Flutter UI design?

Responsiveness deals with how the UI looks on different devices, while adaptiveness is concerned with what the application does on different devices. Signup and view all the answers

What package can be used in Flutter to automatically scale the UI of an application?

responsive_framework Signup and view all the answers

In Flutter, a ticker is used to tell how often an animation is _______.

refreshed Signup and view all the answers

Flutter Inspector is a tool that allows visualization of the blueprint of widgets and their properties in a Flutter application.

True Signup and view all the answers

Which build mode in Flutter is used to minimize the size of the app footprint and optimize performance?

Release Mode Signup and view all the answers

Match the following Flutter database packages with their features:

Firebase database = NoSQL DB, APIs (REST only), Authentication, Analytics, Storage SQFlite database = Serverless, Zero configuration, Open-Source, Compact Signup and view all the answers

What is the purpose of the autocorrect feature in Flutter?

To enable spelling autocorrections Signup and view all the answers

What does the onChanged function provide in Flutter?

Gives the current value of text input by the user Signup and view all the answers

What is the main function of the validator in Flutter?

Enables error description below the TextFormField when the form is submitted Signup and view all the answers

Why might someone want to build a UI widget later in time instead of instantly?

To fetch relevant data from the server Signup and view all the answers

What is the purpose of the FutureBuilder widget in Flutter?

Used when the UI needs to be built with a delay Signup and view all the answers

What is the primary use of the StreamBuilder widget in Flutter?

To build a UI with a continuous stream of inputs Signup and view all the answers

Flutter is a declarative language.

False Signup and view all the answers

What is the key fundamental in the Provider package in Flutter?

Providing something at one node will be known by all of its child widgets Signup and view all the answers

What is the BLoC pattern used for in Flutter applications?

To manage application state Signup and view all the answers

Study Notes

Flutter Overview

Flutter is a highly adaptable and robust framework for crafting applications that work seamlessly across multiple platforms.
It focuses on creating responsive and high-performance user interfaces.
Flutter is a cross-platform UI toolkit that allows applications to interact directly with underlying platform services while allowing code reuse across operating systems.

Architectural Layers of Flutter

Embedder layer: at the bottom of the Flutter framework, directly talks to the underlying operating system, and packages Flutter applications in the same way as native applications.
Engine layer: written in C++, responsible for rasterizing composite scenes, and implements Flutter's basic API at a low level.
Flutter framework: where developers interact to build apps, written in Dart language.

Widgets

Basic building blocks of a Flutter app.
Used to create UI elements, such as text, images, and icons.
Types of widgets:
- StatelessWidget: built only once on the screen, improving performance.
- StatefulWidget: used to update UI elements upon user interaction or state change.

When building a Flutter app, a tree of widgets is created.
The root widget is the MyApp widget, which is called inside the main function of main.dart.

Layouts in Flutter

Widgets are at the heart of Flutter's layout system.
Layout models are also widgets, such as rows, columns, and grids that arrange and align visible widgets.

Common Widgets

Scaffold: a container that holds other UI widgets to build a screen.
Container: a general-purpose widget that can set additional widgets to add decoration or styling.
Column and Row: used to arrange child widgets in a specific direction.
Stack: a widget that holds a list of widgets and arranges them one on top of the other.
ListView: used to arrange children in a scrollable list.
Form: a widget that is used to create forms, such as login or signup forms.

Futures and Streams

Futures: a one-time callback that returns a value when the function is complete.
Streams: a continuous flow of inputs, used to build UI widgets that update in real-time.

State Management

When building apps, there are various states that keep changing because of user interactions.
Flutter is a declarative language, and its user interface is designed to represent the current status of the program.
State management libraries and techniques:
- Provider package: used for state management, provides a value to its underlying widgets.
- Consumer widget: used to rebuild only the part of the UI that is changing.
- BLoC (Business Logic Component) pattern: a reactive programming model that separates the business logic from the UI.

BLoC Pattern

BLoC pattern: a way to manage application state, everything in the app is represented as a stream of events.
BLoC handles stream flow as a go-between based on the logic we specify.
The best part about the BLoC architecture is that it doesn't require importing any libraries or learning new syntax.

Difference between flutter_bloc Library and RxDart

flutter_bloc library: designed specifically for Flutter development, provides a clear separation of concerns.
RxDart: a more general-purpose library that can be used in any Dart project, provides a way to handle complex data flows and streamline development.
RxDart has a steeper learning curve than flutter_bloc when it comes to implementing the BLoC pattern.

### Advantages of RxDart
RxDart's observables can push data, errors, and completion signals, unlike Dart Streams which only emit data events and can throw errors but don't have a built-in completion signal.
A completion signal is useful for determining when to clean up resources associated with the stream or when to perform additional processing after the stream has finished.

Using BLoC for Every Screen

Using BLoC for every screen is a best practice when building an application.
Benefits of using BLoC for every screen:
- Simplifying complex UI logic by separating business logic from presentation logic.
- Enabling unit testing by isolating and testing the functionality of each screen independently.

How to Use BLoC for Every Screen

To use BLoC for every screen:
1. Create a bloc folder in the same folder as your screen.
2. Implement the Bloc/Cubit.
3. Provide the BLoC to the screen using BlocProvider.
4. Use the BLoC for all business logic that needs to be done on the screen.

Keep BLoCs Simple

Each BLoC should have a unique purpose and responsibility.
If a BLoC is handling too many responsibilities, it's a sign that you should be using multiple BLoCs instead.

State Management Methods in Flutter

Inherited widget: a low-level state management solution provided by Flutter that propagates data down the widget tree.
Provider: a popular state management solution in Flutter that uses a simple, lightweight syntax to manage state across applications.
Riverpod: a state management solution in Flutter that's built on top of the Provider package and provides a more intuitive and declarative syntax for managing state.
Redux: a popular state management solution in Flutter that's based on the Redux library from the JavaScript world.
Fish Redux: an implementation of the Redux pattern for state management in Flutter that's designed to simplify state management for complex applications.
GetIt: a simple yet powerful service locator package for Flutter that's great for small- to medium-sized projects where the state is not too complex.

Responsive and Adaptive UI in Flutter

Responsive design: the UI automatically changes the layout based on changes in the number or orientation of available pixels.
Adaptive design: the application changes its functionality depending on what the platform is capable of.

Packages for Responsive Design

responsive_framework: a package that helps make a Flutter application's design responsive by automatically scaling the UI.
responsive_builder: a package that provides widgets that require less code when implementing responsive design.

The Use of Ticker in Flutter

A ticker is used to tell how often an animation is refreshed in Flutter.
Signals are sent at a constant frequency, such as 60 times per second, using this type of signal-sending class.

Flutter Inspector

Flutter Inspector is a powerful tool for Flutter applications that allows you to visualize the blueprint of your widgets and their properties.
Benefits of Flutter Inspector:
- Select widget mode
- Toggle platform
- Show paint baselines
- Show debug paint
- Refresh widget
- Enable slow animations
- Show/hide performance overlay

Execute Code Only in Debug Mode

To execute code only in debug mode:
1. Import the dart foundation.
2. Use kReleaseMode to check if the app is in release mode or debug mode.

The Use of Mixins

Mixins are used to implement multiple inheritance in Flutter/Dart.
Benefits of mixins:
- Making it easy to write reusable class code in multiple class hierarchy levels.
- Providing some utility functions.

Packages and Plugins in Flutter

Packages: collections of classes, interfaces, and sub-packages that enable the creation of modular code that can be shared easily among users.
Plugins: enable more usability and make it easier to use the device.
Difference between packages and plugins:
- Packages: written in the dart programming language.
- Plugins: using native code.

The Flutter Architecture

Upper Layer: consists of the Dart programming language along with the widgets, animations, illustrations, customizations, etc.
Middle Layer or the Flutter Engine: deals with text display, formatting, layout, etc.
Bottom Layer or the built-in service: manages plugins or packages.

Build Modes in Flutter

Debug Mode: enables debugging of apps on a physical device, emulator, or simulator.
Profile Mode: maintains some debugging abilities, enough to analyze the app's performance while testing.

The following command can be used to compile the profile mode: flutter run --profile
Release Mode: used when deploying the app, minimizes the size of the footprint and maximizes optimization.

The following command can be used to compile the release mode: flutter run --release

The Difference Between runApp() and main() in Flutter

main(): starts the program.
runApp(): returns the widgets that are connected to the screen as a root of the widget tree that will be rendered on the screen.

The Difference Between Hot Reload and Hot Restart

Hot Reload: takes approximately one second to perform its functionality, updates the app's UI without destroying the preserved state.
Hot Restart: destroys the preserved state of the app, compiles the code again from the beginning, and takes longer than a hot reload.

BuildContext

BuildContext is used to identify or locate widgets in widget trees.
Each widget has its own BuildContext.
Benefits of BuildContext:
- Finding references to other widgets and themes.
- Interacting with widget parents and accessing widget data.

Pubspec.yaml File

The pubspec.yaml file is a configuration file that contains information about the dependencies, fonts, etc. that a project requires.
Benefits of pubspec.yaml file:
- Ensuring the same package version when building the project.
- Setting constraints for the app.

Create HTTP Requests in Flutter

Use the HTTP package to create HTTP requests.
Example: http.get('<a href="https://jsonplaceholder.typicode.com/albums/1">https://jsonplaceholder.typicode.com/albums/1</a>');

Keys in Flutter

Keys are identifiers for widgets, elements, and semantic nodes.
GlobalKeys and LocalKeys are subclasses of Key.

Database Packages in Flutter

Firebase database: a NoSQL database that provides data sync and quick loading.
SQFlite database: a SQLite database that provides full control over the database, queries, relationships, and anything you could desire.

Limitations of Flutter

Lack of third-party libraries.
Larger release size.
Flutter works with Dart language which is not so advanced as C# or JavaScript.
Not so user-friendly for iOS developers.

Testing Flutter Apps

Types of testing:
- Unit testing: testing individual units of code.
- Widget testing: testing individual widgets in a controlled environment.
- Integration testing: testing how well different units within the app work together.
- User testing: simulating real user interactions with the app to identify usability issues.

Testing Packages for Flutter

Core packages: test package.
Widget testing: flutter_test package.
Mocking: mockito package.

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Explore Flutter, a robust framework for building multi-platform applications with responsive and high-performance UI.