Flutter Questions

Flutter is a framework for building native apps for iOS and Android. It is a toolkit for building beautiful, high-performance, and usable mobile apps.

Some of the advantages of using Flutter are:

• Dart
• Growing popularity
• High performance
• Mild learning curve
• One UI design
• Money and time economy
• Powerful community

Dart is a client-optimized language for developing fast apps on any platform. Its goal is to offer the most productive programming language for multi-platform development, paired with a flexible execution runtime platform for app frameworks.

• Hot reload loads code changes into the VM and re-builds the widget tree, preserving the app state; it doesn’t rerun main() or initState().
• Hot restart loads code changes into the VM, and restarts the Flutter app, losing the app state. 
• Full restart restarts the iOS, Android, or web app. This takes longer because it also recompiles the Java / Kotlin / ObjC / Swift code. On the web, it also restarts the Dart Development Compiler.

BuildContext is a locator that is used to track each widget in a tree and locate them and their position in the tree.

Flutter Inspector is a tool for debugging Flutter apps.

The runApp() function takes the given Widget and makes it the root of the widget tree.

The main() function is the entry point of the application. It is the first function that is called when the application is started.

A Key is an identifier for Widgets, Elements, and SemanticsNodes.

A new widget will only be used to update an existing element if its key is the same as the key of the current widget associated with the element.

For Row

mainAxisAlignment is used to align the children horizontally.

crossAxisAlignment is used to align the children vertically.

For Column

mainAxisAlignment is used to align the children vertically.

crossAxisAlignment is used to align the children horizontally.

Some of the State Management approaches in Flutter are:

• Bloc
• Provider
• Riverpod
• MobX
• setState

Some of the ways to handle persistence in Flutter are:

• Shared Preferences
• SQLite
• File System

SizedBox() is a widget for giving some constant height or width between two widgets. It does not contain any decorative properties just like color, borderRadius etc.

Container() is a convenience widget that combines common painting, positioning, and sizing widgets.

MediaQuery is a widget that provides information about the size and shape of the screen.

• Use stateless widgets.
• Split large widgets into smaller widgets.
• Use the const keyword.
• Render only widgets that are visible on the screen. 
• Avoid using opacity as much as possible.

Profile mode is a mode that is used to profile the performance of your app. It is used to help you identify bottlenecks.

MaterialApp

A convenience widget that wraps a number of widgets that are commonly required for material design applications.

It builds upon a WidgetsApp by adding material-design specific functionality, such as AnimatedTheme and GridPaper.

WidgetsApp

A convenience class that wraps a number of widgets that are commonly required for an application.

One of the primary roles that WidgetsApp provides is binding the system back button to popping the Navigator or quitting the application.

You can perform unit tests, integration tests, and end-to-end tests.

The async patterns in Flutter are:

FutureBuilder: Widget that builds itself based on the latest snapshot of interaction with a Future.

StreamBuilder: Widget that builds itself based on the latest snapshot of interaction with a Stream.

There are two types of build modes in Flutter:

• Debug: This is the default mode. It is used to debug the application.
• Release: This is used to build the application for release.

There are two main types types of widgets in Flutter:

• Stateful widgets: These widgets are used to create UI that is dependent on the state of the application.
• Stateless widgets: These widgets are used to create UI that is independent of the state of the application.

The Flutter SDK has the packages and command-line tools that you need to develop Flutter apps across platforms.

Mixins are a way to create a class that inherits from another class and adds some functionality to it.

Null-aware operators are operators that allow you to use the null-safe operator syntax. For example, you can use ?.  to access the property of a nullable object.

A source of asynchronous data events.

A Stream provides a way to receive a sequence of events. Each event is either a data event, also called an element of the stream, or an error event, which is a notification that something has failed.

When a stream has emitted all its events, a single "done" event notifies the listener that the end has been reached.

There are two kinds of streams: "Single-subscription" streams and "broadcast" streams.

A single-subscription stream allows only a single listener during the whole lifetime of the stream.

It doesn't start generating events until it has a listener, and it stops sending events when the listener is unsubscribed, even if the source of events could still provide more.

The stream created by an async* function is a single-subscription stream, but each call to the function creates a new such stream.

A broadcast stream allows any number of listeners, and it fires its events when they are ready, whether there are listeners or not.

Broadcast streams are used for independent events/observers.

Ticker is a "special" periodic timer that we can use to be notified when the Flutter engine is about to draw a new frame.