CameraKit.java

/**
 * This is a wrapper around the original component to transform
 * interactions from their original callback style to a more
 * reactive approach.
 **/
public final class DJICameraKit {

  private final Camera component;
  
  @Override
  public Observable<CameraMode> getCameraMode() {
    return Observable.fromEmitter(new DJIFunctionWith<CameraMode>() {
        @Override
        public void onCall(DJICompletionCallbackWith<DJICameraSettingsDef.CameraMode> callback) {
            component.getCameraMode(callback);
        }
    }, BackpressureMode.BUFFER);
  }
  
}

CameraKitExample.java

public final class CameraKitExample {
  private final DJICameraKit kit;
  
  publiic void logCameraMode() {
    kit.getCameraMode()
      .subscribe(new Observer<Void>() {
        @Override
        public void onCompleted() {
            // some action.
        }

        @Override
        public void onError(Throwable e) {
          // some action.
        }

        @Override
        public void onNext(Void aVoid) {
          // some action.
        }
    });
  }
}

DJICommonCallbacks.java

/**
 * Originnal callback mechanisms used.
 **/
public class DJICommonCallbacks {

    public DJICommonCallbacks() {
    }

    public interface DJICompletionCallbackWithThreeParam<X, Y, Z> {
        void onSuccess(X var1, Y var2, Z var3);
        void onFailure(DJIError var1);
    }

    public interface DJICompletionCallbackWithTwoParam<X, Y> {
        void onSuccess(X var1, Y var2);
        void onFailure(DJIError var1);
    }

    public interface DJICompletionCallbackWith<T> {
        void onSuccess(T var1);
        void onFailure(DJIError var1);
    }

    public interface DJICompletionCallback {
        void onResult(DJIError var1);
    }
}

DJIFunction.java

/**
 * Convenience method that is passed as a CommonCallback forwards
 * the results to the returned Observable.
 **/
public abstract class DJIFunction implements Action1<Emitter<Void>> {

    @Override
    public void call(final Emitter<Void> emitter) {
        onCall(new DJICompletionCallback() {
            @Override
            public void onResult(DJIError error) {
                if(error == null) {
                    emitter.onNext(null);
                    emitter.onCompleted();
                } else {
                    emitter.onError(new DJIException(error));

                }
            }
        });
    }

    public abstract void onCall(DJICompletionCallback callback);
}