How to build Flutter project with Android aar file?

Question

I want to use Flutter to create an Android app which depends on a third-party SDK that wrapped in an aar file. So far, I have only found the article Accessing Platform and Third-Party Services in Flutter. It seems that I have to build the Flutter project with additional Java files using Android Studio. This is complicated and not what I want. Is there any way to directly load aar files or *.so files in Dart code? Something like how JNI works.

Answer 1

After learning the Flutter example - hello services, I have successfully built my Flutter project with aar file.

Basic Steps:

1. Download the Flutter source code.
2. Open flutter/examples/hello_services/android in Android Studio.
3. Click File > New > New Module and choose Import .JAR/.AAR Package.
4. Press F4 to open Project Structure, and then add the dependent module.
5. Write Java code to invoke APIs that defined in aar file.
6. Import flutter/examples/hello_services to Intellij IDEA.
7. Build and run the Flutter app.

I've pushed the source code to GitHub.

Answer 2

Flutter can be embedded into your existing Android application piecemeal, as a source code Gradle subproject or as AARs.

Depend on the Android Archive (AAR)

This option packages your Flutter library as a generic local Maven repository composed of AARs and POMs artifacts. This option allows your team to build the host app without installing the Flutter SDK. You can then distribute the artifacts from a local or remote repository.

Let’s assume you built a Flutter module at some/path/my_flutter, and then run:

 cd some/path/my_flutter
 flutter build aar

Then, follow the on-screen instructions to integrate.

More specifically, this command creates (by default all debug/profile/release modes) a local repository, with the following files:

build/host/outputs/repo
└── com
    └── example
        └── my_flutter
            ├── flutter_release
            │   ├── 1.0
            │   │   ├── flutter_release-1.0.aar
            │   │   ├── flutter_release-1.0.aar.md5
            │   │   ├── flutter_release-1.0.aar.sha1
            │   │   ├── flutter_release-1.0.pom
            │   │   ├── flutter_release-1.0.pom.md5
            │   │   └── flutter_release-1.0.pom.sha1
            │   ├── maven-metadata.xml
            │   ├── maven-metadata.xml.md5
            │   └── maven-metadata.xml.sha1
            ├── flutter_profile
            │   ├── ...
            └── flutter_debug
                └── ...

To depend on the AAR, the host app must be able to find these files.

To do that, edit app/build.gradle in your host app so that it includes the local repository and the dependency:

android {
  // ...
}

repositories {
  maven {
    url 'some/path/my_flutter/build/host/outputs/repo'
    // This is relative to the location of the build.gradle file
    // if using a relative path.
  }
  maven {
    url 'https://storage.googleapis.com/download.flutter.io'
  }
}

dependencies {
  // ...
  debugImplementation 'com.example.flutter_module:flutter_debug:1.0'
  profileImplementation 'com.example.flutter_module:flutter_profile:1.0'
  releaseImplementation 'com.example.flutter_module:flutter_release:1.0'
}

Tip: You can also build an AAR for your Flutter module in Android Studio using the Build > Flutter > Build AAR menu.

Your app now includes the Flutter module as a dependency. You can follow the next steps in the Adding a Flutter screen to an Android app.

For more info, see Integrate a Flutter module into your Android project