Flutter documentation

Flutter documentation

New to Flutter?

Once you’ve gone through Get started, including Write your first Flutter app, here are some next steps.

Docs

Coming from another platform? Check out Flutter for: Android, SwiftUI, UIKit, React Native, and Xamarin.Forms developers.

Building layouts

Learn how to create layouts in Flutter, where everything is a widget.

Understanding constraints

Once you understand that “Constraints flow down. Sizes flow up. Parents set positions”, then you are well on your way to understanding Flutter’s layout model.

Adding interactivity to your Flutter app

Learn how to add a stateful widget to your app.

A tour of the Flutter widget framework

Learn more about Flutter’s react-style framework.

FAQ

Get the answers to frequently asked questions.

Install

Set up an editor

You can build apps with Flutter using any text editor combined with Flutter’s command-line tools. However, we recommend using one of our editor plugins for an even better experience. These plugins provide you with code completion, syntax highlighting, widget editing assists, run & debug support, and more.

Use the following steps to add an editor plugin for VS Code, Android Studio, IntelliJ, or Emacs. If you want to use a different editor, that’s OK, skip ahead to the next step: Test drive.

nstall VS Code

VS Code is a lightweight editor with complete Flutter app execution and debug support.

• VS Code, latest stable version

Install the Flutter and Dart plugins

1. Start VS Code.
2. Invoke View > Command Palette….
3. Type “install”, and select Extensions: Install Extensions.
4. Type “flutter” in the extensions search field, select Flutter in the list, and click Install. This also installs the required Dart plugin.

Validate your setup with the Flutter Doctor

1. Invoke View > Command Palette….
2. Type “doctor”, and select the Flutter: Run Flutter Doctor.
3. Review the output in the OUTPUT pane for any issues. Make sure to select Flutter from the dropdown in the different Output Options.

Test drive

1. Get started

This page describes how to create a new Flutter app from templates, run it, and experience “hot reload” after you make changes to the app.

Select your development tool of choice for writing, building, and running Flutter apps.

Create the app

1. Invoke View > Command Palette.
2. Type “flutter”, and select the Flutter: New Project.
3. Select Application.
4. Create or select the parent directory for the new project folder.
5. Enter a project name, such as my_app, and press Enter.
6. Wait for project creation to complete and the main.dart file to appear.

The above commands create a Flutter project directory called my_app that contains a simple demo app that uses

The above commands create a Flutter project directory called my_app that contains a simple demo app that uses Material Components.

 Note: When creating a new Flutter app, some Flutter IDE plugins ask for a company domain name in reverse order, something like com.example. The company domain name and project name are used together as the package name for Android (the Bundle ID for iOS) when the app is released. If you think that the app might be released, it’s better to specify the package name now. The package name can’t be changed once the app is released, so make the name unique.

 Warning: If VS Code was running during your initial Flutter setup, you might need to restart it for VS Code’s Flutter plugin to detect the Flutter SDK.

 Tip: The code for your app is in lib/main.dart. For a high-level description of what each code block does, see the comments at the top of that fil

Run the app

1. Locate the VS Code status bar (the blue bar at the bottom of the window):
   
2. Select a device from the Device Selector area. For details, see Quickly switching between Flutter devices.

• If no device is available, and you want to use a device simulator, click No Devices and click Start iOS Simulator to launch a simulator.

   Warning: You might not see Start iOS Simulator option when you click No Devices in VS Code. If you’re on Mac, then you might have to run following command in terminal to launch a simulator.

  $ open -a simulator
  

  On Windows or Linux, it’s not possible to launch

1. • To setup a real device, follow the device-specific instructions on the Install page for your OS.

2. Invoke Run > Start Debugging or press F5.
3. Wait for the app to launch—progress is printed in the Debug Console view.

After the app build completes, you’ll see the starter app on your device.

Try hot reload

Flutter offers a fast development cycle with Stateful Hot Reload, the ability to reload the code of a live running app without restarting or losing app state. Make a change to app source, tell your IDE or command-line tool that you want to hot reload, and see the change in your simulator, emulator, or device.

1. Open lib/main.dart.

2. Change the string

   'You have pushed the button this many times'

   to

   'You have clicked the button this many times'

    Important: Do not stop your app. Let your app run.

1. Save your changes: invoke Save All, or click Hot Reload  .

You’ll see the updated string in the running app almost immediately.

Profile or release runs

 Important: Do not test the performance of your app with debug and hot reload enabled.

So far you’ve been running your app in debug mode. Debug mode trades performance for useful developer features such as hot reload and step debugging. It’s not unexpected to see slow performance and janky animations in debug mode. Once you are ready to analyze performance or release your app, you’ll want to use Flutter’s “profile” or “release” build modes. For more details, see Flutter’s build modes.

 Important: If you’re concerned about the package size of your app, see Measuring your app’s size.

Write your first Flutter app

You are now ready to start the “First Flutter app” codelab. In about an hour and a half, you will learn the basics of Flutter by creating an app that works on mobile, desktop, and web.