Android Studio - draw face detection on camera preview (Real time face detection)

Question

I created a basic app that display the frontal camera of the phone. I need to use the Google Servies face detector to draw rectangle around the face (on the FrameLayout, that contain the camera preview data). I know the basic usage of the face detector and i know how to detect face in image view. Someone can Help me to apply the face detection on the frame layout of my app? Thanks a lot.

My code:

public class MainActivity extends AppCompatActivity {

private ImageSurfaceView mImageSurfaceView;
private Camera camera;
private FrameLayout cameraPreviewLayout;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

    cameraPreviewLayout = (FrameLayout)findViewById(R.id.camera_preview);

    camera = checkDeviceCamera();

    mImageSurfaceView = new ImageSurfaceView(MainActivity.this, camera);
    mImageSurfaceView.draw(canvas);
    cameraPreviewLayout.addView(mImageSurfaceView);
}


private Camera checkDeviceCamera() {
    Camera mCamera = null;
    try {
        mCamera = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT); // set the cameras to the front (selfi)
    } catch (Exception e) {
        e.printStackTrace();
    }
    return mCamera;
} 
}

ImageSurfaceView Class:

public class ImageSurfaceView extends SurfaceView implements   SurfaceHolder.Callback {

private Camera camera;
private SurfaceHolder surfaceHolder;

public ImageSurfaceView(Context context, Camera camera) {
    super(context);
    this.camera = camera;

    this.surfaceHolder = getHolder();
    this.surfaceHolder.addCallback(this);
}

@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
    try {
        this.camera.setPreviewDisplay(surfaceHolder);
        this.camera.startPreview();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
}

@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
    this.camera.startPreview();
    this.camera.release();
}