How to export Unity to a Flutter plugin

[laurentP22]

Hi, I'm currently working on a Flutter app and would like to export Unity into an external Flutter plugin. The purpose of moving Unity integration to a separate plugin is to simplify our development process by:

• Having a specific example app to test the Unity integration independently.
• Reducing the number of files in the main app.
• Sharing the Unity code between multiple apps.

Until now, I've been focused on the Android integration. I've found two related topics on StackOverflow, but neither solution worked for me:

• Using Flutter Unity Widget and create a plugin with my Unity project
• How do I add library module dependency to a Flutter plugin’s Android folder correctly?

What I tried:

• Created a new Flutter plugin named "bridge": flutter create --org com.example --template=plugin --platforms=android bridge
• Added the DemoApp Unity project from the example app of this repository to the plugin (path: bridge/unity/DemoApp).
• Opened the DemoApp project in Unity.
• Executed Flutter -> Export Android Release.
  • The unityLibrary folder is correctly generated (path: bridge/android/unityLibrary).
• Updated bridge/android/settings.gradle to convert the unityLibrary folder into a module:

rootProject.name = 'bridge'

include ":unityLibrary"
project(":unityLibrary").projectDir = file("./unityLibrary")

• Updated bridge/android/build.gradle to add the directory to the repositories:

allprojects {
    repositories {
        flatDir {
            dirs "unityLibrary/libs"
        }

        google()
        mavenCentral()
    }
}

• Updated bridge/android/build.gradle to implement the module:

dependencies {
    implementation project(':unityLibrary')
}

• When building the example app, it fails with:

FAILURE: Build failed with an exception.

* Where:
Build file '.../bridge/android/build.gradle' line: 76 // <-- Corresponds to `implementation project(':unityLibrary')`

* What went wrong:
A problem occurred evaluating project ':bridge'.
> Project with path ':unityLibrary' could not be found in project ':bridge'.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
> Get more help at https://help.gradle.org.

BUILD FAILED in 381ms
Error: Gradle task assembleDebug failed with exit code 1

I tried several configurations, but it always fails to build. I'm really not an expert in Android and Gradle configuration, so I might be missing something, or not configuring the project correctly. Or maybe it's actually not possible to do...

Has anyone successfully achieved such an integration?

Thanks for your assistance!