Using packages

Flutter supports using shared packages contributed by other developers to the Flutter and Dart ecosystems. This allows quickly building an app without having to develop everything from scratch.

Existing packages enable many use cases—for example, making network requests (http), navigation/route handling (go_router), integration with device APIs (url_launcher and battery_plus), and using third-party platform SDKs like Firebase (FlutterFire).

To write a new package, see developing packages. To add assets, images, or fonts, whether stored in files or packages, see Adding assets and images.

The following section describes how to use existing published packages.

Packages are published to pub.dev.

The Flutter landing page on pub.dev displays top packages that are compatible with Flutter (those that declare dependencies generally compatible with Flutter), and supports searching among all published packages.

The Flutter Favorites page on pub.dev lists the plugins and packages that have been identified as packages you should first consider using when writing your app. For more information on what it means to be a Flutter Favorite, see the Flutter Favorites program.

You can also browse the packages on pub.dev by filtering on Android, iOS, web, Linux, Windows, macOS, or any combination thereof.

To add the package, css_colors, to an app:

1. Depend on it

   • Open the pubspec.yaml file located inside the app folder, and add css_colors: under dependencies.

2. Install it

   • From the terminal: Run flutter pub get.
     OR
   • From VS Code: Click Get Packages located in right side of the action ribbon at the top of pubspec.yaml indicated by the Download icon.
   • From Android Studio/IntelliJ: Click Pub get in the action ribbon at the top of pubspec.yaml.

3. Import it

   • Add a corresponding import statement in the Dart code.

4. Stop and restart the app, if necessary

   • If the package brings platform-specific code (Kotlin/Java for Android, Swift/Objective-C for iOS), that code must be built into your app. Hot reload and hot restart only update the Dart code, so a full restart of the app might be required to avoid errors like MissingPluginException when using the package.

To add the package, css_colors, to an app:

1. Issue the command while being inside the project directory

   • flutter pub add css_colors

2. Import it

   • Add a corresponding import statement in the Dart code.

3. Stop and restart the app, if necessary

   • If the package brings platform-specific code (Kotlin/Java for Android, Swift/Objective-C for iOS), that code must be built into your app. Hot reload and hot restart only update the Dart code, so a full restart of the app might be required to avoid errors like MissingPluginException when using the package.

To remove the package, css_colors, to an app:

1. Issue the command while being inside the project directory
   • flutter pub remove css_colors

The Installing tab, available on any package page on pub.dev, is a handy reference for these steps.

For a complete example, see the css_colors example below.

Suppose you want to use some_package and another_package in an app, and both of these depend on url_launcher, but in different versions. That causes a potential conflict. The best way to avoid this is for package authors to use version ranges rather than specific versions when specifying dependencies.

dependencies:
  url_launcher: ^5.4.0    # Good, any version >= 5.4.0 but < 6.0.0
  image_picker: '5.4.3'   # Not so good, only version 5.4.3 works.

If some_package declares the dependencies above and another_package declares a compatible url_launcher dependency like '5.4.6' or ^5.5.0, pub resolves the issue automatically. Platform-specific dependencies on Gradle modules and/or CocoaPods are solved in a similar way.

Even if some_package and another_package declare incompatible versions for url_launcher, they might actually use url_launcher in compatible ways. In this situation, the conflict can be resolved by adding a dependency override declaration to the app's pubspec.yaml file, forcing the use of a particular version.

For example, to force the use of url_launcher version 5.4.0, make the following changes to the app's pubspec.yaml file:

dependencies:
  some_package:
  another_package:
dependency_overrides:
  url_launcher: '5.4.0'

If the conflicting dependency is not itself a package, but an Android-specific library like guava, the dependency override declaration must be added to Gradle build logic instead.

To force the use of guava version 28.0, make the following changes to the app's android/build.gradle file:

configurations.all {
    resolutionStrategy {
        force 'com.google.guava:guava:28.0-android'
    }
}

CocoaPods doesn't currently offer dependency override functionality.

If no package exists for your specific use case, you can write a custom package.

To minimize the risk of version collisions, specify a version range in the pubspec.yaml file.

All packages have a version number, specified in the package's pubspec.yaml file. The current version of a package is displayed next to its name (for example, see the url_launcher package), as well as a list of all prior versions (see url_launcher versions).

To ensure that the app doesn't break when you update a package, specify a version range using one of the following formats.

• Ranged constraints: Specify a minimum and maximum version.

  yaml

  dependencies:
    url_launcher: '>=5.4.0 <6.0.0'

• Ranged constraints using the caret syntax: Specify the version that serves as the inclusive minimum version. This covers all versions from that version to the next major version.

  yaml

  dependencies:
    collection: '^5.4.0'

  This syntax means the same as the one noted in the first bullet.

To learn more, check out the package versioning guide.

When running flutter pub get for the first time after adding a package, Flutter saves the concrete package version found in the pubspec.lock lockfile. This ensures that you get the same version again if you, or another developer on your team, run flutter pub get.

To upgrade to a new version of the package, for example to use new features in that package, run flutter pub upgrade to retrieve the highest available version of the package that is allowed by the version constraint specified in pubspec.yaml. Note that this is a different command from flutter upgrade or flutter update-packages, which both update Flutter itself.

Packages can be used even when not published on pub.dev. For private packages, or for packages not ready for publishing, additional dependency options are available:

Path dependency

A Flutter app can depend on a package using a file system path: dependency. The path can be either relative or absolute. Relative paths are evaluated relative to the directory containing pubspec.yaml. For example, to depend on a package, packageA, located in a directory next to the app, use the following syntax:

yaml

  dependencies:
  packageA:
    path: ../packageA/

Git dependency

You can also depend on a package stored in a Git repository. If the package is located at the root of the repo, use the following syntax:

yaml

  dependencies:
    packageA:
      git:
        url: https://github.com/flutter/packageA.git

Git dependency using SSH

If the repository is private and you can connect to it using SSH, depend on the package by using the repo's SSH url:

yaml

  dependencies:
    packageA:
      git:
        url: git@github.com:flutter/packageA.git

Git dependency on a package in a folder

Pub assumes the package is located in the root of the Git repository. If that isn't the case, specify the location with the path argument. For example:

yaml

dependencies:
  packageA:
    git:
      url: https://github.com/flutter/packages.git
      path: packages/packageA

Finally, use the ref argument to pin the dependency to a specific git commit, branch, or tag. For more details, see Package dependencies.

The following examples walk through the necessary steps for using packages.

The css_colors package defines color constants for CSS colors, so use the constants wherever the Flutter framework expects the Color type.

To use this package:

1. Create a new project called cssdemo.

2. Open pubspec.yaml, and add the css-colors dependency:

   yaml

   dependencies:
     flutter:
       sdk: flutter
     css_colors: ^1.0.0

3. Run flutter pub get in the terminal, or click Get Packages in VS Code.

4. Open lib/main.dart and replace its full contents with:

   dart

   import 'package:css_colors/css_colors.dart';
   import 'package:flutter/material.dart';
   
   void main() {
     runApp(const MyApp());
   }
   
   class MyApp extends StatelessWidget {
     const MyApp({super.key});
   
     @override
     Widget build(BuildContext context) {
       return const MaterialApp(
         home: DemoPage(),
       );
     }
   }
   
   class DemoPage extends StatelessWidget {
     const DemoPage({super.key});
   
     @override
     Widget build(BuildContext context) {
       return Scaffold(body: Container(color: CSSColors.orange));
     }
   }

1. Run the app. The app's background should now be orange.

The url_launcher plugin package enables opening the default browser on the mobile platform to display a given URL, and is supported on Android, iOS, web, Windows, Linux, and macOS. This package is a special Dart package called a plugin package (or plugin), which includes platform-specific code.

To use this plugin:

1. Create a new project called launchdemo.

2. Open pubspec.yaml, and add the url_launcher dependency:

   yaml

   dependencies:
     flutter:
       sdk: flutter
     url_launcher: ^5.4.0

3. Run flutter pub get in the terminal, or click Get Packages get in VS Code.

4. Open lib/main.dart and replace its full contents with the following:

   dart

   import 'package:flutter/material.dart';
   import 'package:path/path.dart' as p;
   import 'package:url_launcher/url_launcher.dart';
   
   void main() {
     runApp(const MyApp());
   }
   
   class MyApp extends StatelessWidget {
     const MyApp({super.key});
   
     @override
     Widget build(BuildContext context) {
       return const MaterialApp(
         home: DemoPage(),
       );
     }
   }
   
   class DemoPage extends StatelessWidget {
     const DemoPage({super.key});
   
     void launchURL() {
       launchUrl(p.toUri('https://flutter.dev'));
     }
   
     @override
     Widget build(BuildContext context) {
       return Scaffold(
         body: Center(
           child: ElevatedButton(
             onPressed: launchURL,
             child: const Text('Show Flutter homepage'),
           ),
         ),
       );
     }
   }

5. Run the app (or stop and restart it, if it was already running before adding the plugin). Click Show Flutter homepage. You should see the default browser open on the device, displaying the homepage for flutter.dev.

Unless stated otherwise, the documentation on this site reflects the latest stable version of Flutter. Page last updated on 2024-07-06. View source or report an issue.