• Use release mode for deploying the app, when you want maximum optimization and minimal footprint size.
• Use release mode when you are ready to release your app.
• For mobile, release mode (which is not supported on the simulator or emulator), means that: – Assertions are disabled. – Debugging information is stripped out. – Debugging is disabled. – Compilation is optimized for fast startup, fast execution, and small package sizes. Service extensions are disabled.
• Release mode for a web app means that: – The build is minified and tree shaking has been performed. – The app is compiled with the dart2js compiler for best performance.
• The command flutter run --release compiles to release mode.
• You can compile to release mode for a specific target with flutter build <target>.

What is profile mode and when do you use it?

• In profile mode, some debugging ability is maintained—enough to profile your app’s performance.
• Profile mode is used when you want to analyze performance.
• Profile mode is disabled on the emulator and simulator, because their behavior is not representative of real performance.
• On mobile, profile mode is similar to release mode, with the following differences: – Some service extensions, such as the one that enables the performance overlay, are enabled. – Tracing is enabled, and tools supporting source-level debugging (such as DevTools) can connect to the process.
• Profile mode for a web app means that: – The build is not minified but tree shaking has been performed. – The app is compiled with the dart2js compiler.
• The command flutter run --profile compiles to profile mode.

What is release mode and when do you use it?

• Dart offers some handy operators for dealing with values that might be null.
• One is the ??= assignment operator, which assigns a value to a variable only if that variable is currently null:

	int a; // The initial value of a is null.
	a ??= 3;
	print(a); // <-- Prints 3.

	a ??= 5;
	print(a); // <-- Still prints 3.

Another null-aware operator is ??, which returns the expression on its left unless that expression’s value is null, in which case it evaluates and returns the expression on its right:

print(1 ?? 3); // <-- Prints 1.
	print(null ?? 12); // <-- Prints 12.

Hot Reload

• Flutter hot reload features works with combination of Small r key on command prompt or Terminal.
• Hot reload feature quickly compile the newly added code in our file and sent the code to Dart Virtual Machine. After done updating the Code Dart Virtual Machine update the app UI with widgets.
• Hot Reload takes less time then Hot restart.
• There is also a draw back in Hot Reload, If you are using States in your application then Hot Reload preservers the States so they will not update on Hot Reload our set to their default values.

Hot Restart

• Hot restart is much different than hot reload.
• In Hot restart it destroys the preserves State value and set them to their default. So if you are using States value in your application then after every hot restart the developer gets fully compiled application and all the states will be set to their defaults.
• The app widget tree is completely rebuilt with new typed code.
• Hot Restart takes much higher time than Hot reload.

someObjects.sort((a, b) => a.someProperty.compareTo(b.someProperty));

On your MaterialApp set debugShowCheckedModeBanner to false.

MaterialApp(
debugShowCheckedModeBanner: false,
)

The debug banner will also automatically be removed on release build.

In Flutter(Dart), Colors are represented as a 32 bit value(or 8 hex characters).

0x this tells the compiler we are about to write a hexadecimal number, so if you wanted to write this Color in a decimal representation, you can, like this:
Color(4294728333).

0xfffc5a8d == 4294728333

Hex is just easier to read, so please use hex 🙂

Every Color in Flutter is made of 4 components(look at the image above): Alpha, Red, Green and Blue. All of them are 2 hex characters long.

Alpha(white underline) – This is how transparent your colors is. 00 totally transparent, FF not transparent at all.
Red(red underline) – Red component. It ranges from 00-ff.
Green(green underline) – Green component. It ranges from 00-ff.
Blue(blue underline) – Blue component. It ranges from 00-ff.

Read more: RGB And Hex Color Codes In Flutter

Whether you are building a mobile app or a web application, State Management is crucial. Using it, states of various UI controls are centralized to handle data flow across an application. It can be a text field, radio button, checkbox, dropdown, toggle, form, and so on. In Flutter, state management can be categorized into two types as follows:

• Ephemeral State: Ephemeral state is also called UI state or local state, and it pertains to a particular widget. In other words, it is a state that is contained within the specific widget. By means of StatefulWidget, Flutter provides support for this state.
• App State: This is different from the ephemeral state since it is a state that we intend to share across different parts of the app and which we want to maintain between sessions. These types of states can thus be used globally. By means of scoped_model, Flutter provides support for this state.

The streams’ functionality is part of Dart and is inherited by Flutter. In Flutter, there are two kinds of streams:

• Single Subscription Streams: These streams deliver events sequentially. They are considered as sequences contained within a larger whole. These streams are used when the order in which events are received matters, such as reading a file. There can be only one listener throughout the sequence, and without a listener, the event won’t be triggered.
• Broadcast Streams: These streams deliver events to their subscribers. Upon subscribing to events, subscribers are immediately able to start listening to them.  These are versatile streams that allow several listeners to listen simultaneously. Furthermore, one can listen again even after canceling a previous subscription

In flutter, widgets can be divided into two categories:

• Stateless Widget: A widget that does nothing is a Stateless Widget. In essence, they are static and don’t store any state.   Thus, they don’t save values that may change.
• Stateful Widget: A widget that does anything is a Stateful Widget. Stateful widgets are dynamic by nature, which means they can monitor changes and update the UI accordingly.

Flutter widgets are built using a modern framework that takes inspiration from React. The central idea is that you build your UI out of widgets. Widgets describe what their view should look like given their current configuration and state. When a widget’s state changes, the widget rebuilds its description, which the framework diffs against the previous description in order to determine the minimal changes needed in the underlying render tree to transition from one state to the next.

Learn more about i18n and l10n in the internationalization tutorial.

Learn more about a11y in the accessibility documentation.

Yes. Flutter gives developers out-of-the-box access to some platform-specific services and APIs from the operating system. However, we want to avoid the “lowest common denominator” problem with most cross-platform APIs, so we don’t intend to build cross-platform APIs for all native services and APIs.

A number of platform services and APIs have ready-made packages available on pub.dev. Using an existing package is easy.

Finally, we encourage developers to use Flutter’s asynchronous message passing system to create your own integrations with platform and third-party APIs. Developers can expose as much or as little of the platform APIs as they need, and build layers of abstractions that are a best fit for their project.

Yes, learn more in the add-to-app section of our website. Also, note that experimental support for adding multiple Flutter screens or views is available.

Yes, desktop support is in beta for Windows, macOS, and Linux, but a snapshot of the beta is available on the stable channel.) The current progress is documented on the Desktop page.

Yes, web support is available in the stable channel. You can compile existing Flutter code to work on the web. For more details, check out the web instructions.

• Flutter support and test running Flutter on a variety of low-end to high-end platforms. For a detailed list of the platforms on which we test, see the list of supported platforms.
• Flutter supports building ahead-of-time (AOT) compiled libraries for x86_64, armeabi-v7a, and arm64-v8a.
• Apps built for ARMv7 or ARM64 run fine (using ARM emulation) on many x86 Android devices.
• We support developing Flutter apps on a range of platforms. See the system requirements listed under each development operating system.

You can compile and deploy your Flutter app to iOS, Android, web, and desktop (in beta). While more adventurous developers are already deploying Flutter desktop apps, you might want to wait for desktop support to migrate to the stable channel if you are uncomfortable living on the edge. (However, a snapshot of beta desktop support is available on the stable channel, so you can try it out.)

Hot reload works by injecting updated source code files into the running Dart VM (Virtual Machine). This doesn’t only add new classes, but also adds methods and fields to existing classes, and changes existing functions. Hot restart resets the state to the app’s initial state.

For more information, see Hot reload.

Flutter implements a hot reload developer cycle. You can expect sub-second reload times, on a device or an emulator/simulator.

Flutter’s hot reload is stateful, which means the app state is retained after a reload. This means you can quickly iterate on a screen deeply nested in your app, without starting from the home screen after every reload.

You can expect excellent performance. Flutter is designed to help developers easily achieve a constant 60fps. Flutter apps run via natively compiled code—no interpreters are involved. This means that Flutter apps start quickly

No. Instead, Flutter provides a set of widgets (including Material Design and Cupertino (iOS-styled) widgets), managed and rendered by Flutter’s framework and engine. You can browse a catalog of Flutter’s widgets.

We believe that the end result is higher quality apps. If we reused the built-in platform widgets, the quality and performance of Flutter apps would be limited by the flexibility and quality of those widgets.

In Android, for example, there’s a hard-coded set of gestures and fixed rules for disambiguating them. In Flutter, you can write your own gesture recognizer that is a first class participant in the gesture system. Moreover, two widgets authored by different people can coordinate to disambiguate gestures.

Modern app design trends point towards designers and users wanting more motion-rich UIs and brand-first designs. In order to achieve that level of customized, beautiful design, Flutter is architectured to drive pixels instead of the built-in widgets.

By using the same renderer, framework, and set of widgets, it’s easier to publish for multiple platforms from the same codebase, without having to do careful and costly planning to align different feature sets and API characteristics.

By using a single language, a single framework, and a single set of libraries for all of your code (regardless if your UI is different for each platform or not), we also aim to help lower app development and maintenance costs.

The engine’s C and C++ code are compiled with LLVM. The Dart code (both the SDK’s and yours) are ahead-of-time (AOT) compiled into a native, ARM library. That library is included in a “runner” iOS project, and the whole thing is built into an .ipa. When launched, the app loads the Flutter library. Any rendering, input or event handling, and so on, are delegated to the compiled Flutter and app code. This is similar to the way many game engines work.

During debug mode, Flutter uses a virtual machine (VM) to run its code in order to enable stateful hot reload, a feature that lets you make changes to your running code without recompilation. You’ll see a “debug” banner in the top right-hand corner of your app when running in this mode, to remind you that performance is not characteristic of the finished release app.

The engine’s C and C++ code are compiled with Android’s NDK. The Dart code (both the SDK’s and yours) are ahead-of-time (AOT) compiled into native, ARM, and x86 libraries. Those libraries are included in a “runner” Android project, and the whole thing is built into an .apk. When launched, the app loads the Flutter library. Any rendering, input, or event handling, and so on, is delegated to the compiled Flutter and app code. This is similar to the way many game engines work.

During debug mode, Flutter uses a virtual machine (VM) to run its code in order to enable stateful hot reload, a feature that lets you make changes to your running code without recompilation. You’ll see a “debug” banner in the top right-hand corner of your app when running in this mode, to remind you that performance is not characteristic of the finished release app.

Flutter is built with C, C++, Dart, and Skia (a 2D rendering engine). See this architecture diagram for a better picture of the main components. For a more detailed description of the layered architecture of Flutter, read the architectural overview.

Yes, Flutter comes with Flutter DevTools (also called Dart DevTools). For more information, see Debugging with Flutter and the Flutter DevTools docs.

Yes, Flutter provides APIs for writing unit and integration tests. Learn more about testing with Flutter.

We use our own testing capabilities to test our SDK, and we measure our test coverage on every commit.

Yes! Flutter ships with a set of high-quality Material Design and Cupertino (iOS-style) widgets, layouts, and themes. Of course, these widgets are only a starting point. Flutter is designed to make it easy to create your own widgets, or customize the existing widgets.

Yes! Flutter ships with a modern react-style framework. Flutter’s framework is designed to be layered and customizable (and optional). Developers can choose to use only parts of the framework, or even replace upper layers of the framework entirely.

We provide plugins for Android Studio, IntelliJ IDEA, and VS Code. See editor configuration for setup details, and Android Studio/IntelliJ and VS Code for tips on how to use the plugins.

Alternatively, you can use the flutter command from a terminal, along with one of the many editors that support editing Dart.

Flutter includes:

• Heavily optimized, mobile-first 2D rendering engine with excellent support for text
• Modern react-style framework
• Rich set of widgets implementing Material Design and iOS-style
• APIs for unit and integration tests
• Interop and plugin APIs to connect to the system and 3rd-party SDKs
• Headless test runner for running tests on Windows, Linux, and Mac
• Dart DevTools for testing, debugging, and profiling your app
• Command-line tools for creating, building, testing, and compiling your apps

Flutter is different than most other options for building mobile apps because it doesn’t rely on web browser technology nor the set of widgets that ship with each device. Instead, Flutter uses its own high-performance rendering engine to draw widgets.

In addition, Flutter is different because it only has a thin layer of C/C++ code. Flutter implements most of its system (compositing, gestures, animation, framework, widgets, etc) in Dart (a modern, concise, object-oriented language) that developers can easily approach read, change, replace, or remove. This gives developers tremendous control over the system, as well as significantly lowers the bar to approachability for the majority of the system.

Flutter is an open source project, with contributions from Google and other companies and individuals.

Flutter is designed to support mobile apps that run on both Android and iOS, as well as interactive apps that you want to run on your web pages or on the desktop. (Note that desktop support is in beta, but a snapshot of the beta is available on the stable channel.)

Apps that need to deliver highly branded designs are particularly well suited for Flutter. However, you can also create pixel-perfect experiences that match the Android and iOS design languages with Flutter.

Flutter’s package ecosystem supports a wide variety of hardware (such as camera, GPS, network, and storage) and services (such as payments, cloud storage, authentication, and ads).

Flutter is approachable to programmers familiar with object-oriented concepts (classes, methods, variables, etc) and imperative programming concepts (loops, conditionals, etc).

We have seen people with very little programming experience learn and use Flutter for prototyping and app development

For users, Flutter makes beautiful apps come to life.

For developers, Flutter lowers the bar to entry for building apps. It speeds app development and reduces the cost and complexity of app production across platforms.

For designers, Flutter provides a canvas for high-end user experiences. Fast Company described Flutter as one of the top design ideas of the decade for its ability to turn concepts into production code without the compromises imposed by typical frameworks. It also acts as a productive prototyping tool, with CodePen support for sharing your ideas with others.

For engineering managers and businesses, Flutter allows the unification of app developers into a single mobile, web, and desktop app team, building branded apps for multiple platforms out of a single codebase. Flutter speeds feature development and synchronizes release schedules across the entire customer base.

Flutter is Google’s portable UI toolkit for crafting beautiful, natively compiled applications for mobile, web, and desktop from a single codebase. Flutter works with existing code, is used by developers and organizations around the world, and is free and open source.