JNI thorws StateError when execute CameraX initializationFuture.await

[yanshouwang]

The CameraX library's CameraController class has a getInitializationFuture() method.

I wrote a wrapper of this method and generate binding method with jnigen.

# Run with `dart run jnigen --config jnigen.yaml`.
android_sdk_config:
  add_gradle_deps: true
  android_example: example/
suspend_fun_to_async: true
log_level: all
output:
  dart:
    path: lib/src/jni/
class_path:
  - classes/jetified-listenablefuture-1.0.jar
classes:
  - android.app.Activity
  - android.content.Context
  - androidx.lifecycle.LifecycleOwner
  - androidx.lifecycle.LiveData
  - androidx.lifecycle.Observer
  - dev.hebei.camerax_android.core.CameraSelector
  - dev.hebei.camerax_android.core.PermissionManager
  - dev.hebei.camerax_android.core.ZoomState
  - dev.hebei.camerax_android.view.CameraController
  - dev.hebei.camerax_android.view.LifecycleCameraController
  - dev.hebei.camerax_android.view.PreviewView

abstract class CameraController {
    internal abstract val obj: androidx.camera.view.CameraController

    suspend fun initialize() {
        obj.initializationFuture.await()
    }
...
}

final class CameraControllerImpl {
  final jni.LifecycleCameraController obj;
...
  @override
  Future<void> initialize() async {
    await obj.initialize();
  }
...
}

The app throws StateError when calling this method.

    try {
      await controller.initialize();
      await controller.setCameraSelector(CameraSelector.back);
      await bind();
    } catch (e, stack) {
      logger.severe(e, stack);
    }

[HomeViewModel] Bad state: The reference was null
[HomeViewModel] #0      new JObject.fromReference (package:jni/src/jobject.dart:105:7)
                #1      JObjectType.fromReference (package:jni/src/jobject.dart:61:15)
jobject.dart:61
                #2      CameraController.initialize (package:camerax_android/src/jni/dev/hebei/camerax_android/view/CameraController.dart:96:38)
CameraController.dart:96
                <asynchronous suspension>
                #3      CameraControllerImpl.initialize (package:camerax_android/src/view/camera_controller_impl.dart:41:5)
camera_controller_impl.dart:41
                <asynchronous suspension>
                #4      HomeViewModel._initialize (package:camerax_android_example/view_models/home_view_model.dart:216:7)
home_view_model.dart:216
                <asynchronous suspension>

[yanshouwang]

I think jnigen has a bug when generating return value of Void type.

public final class Void {
    public static final Class<Void> TYPE = null;

    Void() {
        throw new RuntimeException("Stub!");
    }
}