CODEWITHSUNDEEP
androidopencvserviceandroid-activitysurfaceview
BCL
BCL

Reputation: 157

Sending OpenCV image (or bitmap) from Service to Activity (SurfaceView)

I'm developing an Android application that installs a service that does some continuously and costly processing (it leverages OpenCV to grab camera images and does some processing on it). I want my activity to connect to and disconnect from the service to do other things on the device and to view the processing (mainly for debugging but I can see other use cases as well).

Problem is I'm not sure how to design this application - I'm also fairly new to Android programming.

Since its a performance critical application I guess I cannot pass bitmaps from the service to the activity so I guess I want to couple the SurfaceView to the service as soon as the activity gets to the foreground.

Something like below - note: its not a complete example, it just shows the flow

public class MainActivity extends Activity {
    private OpenCVCameraService mService;
    private SurfaceView mSurfaceView;
    @Override
    public void onCreate() {
        // show UI
        // start mService with mSurfaceView
    }
}

public class OpenCVCameraService extends Service {
    private Processing mProcessing;
    private SurfaceView mSurfaceView;
    @Override
    public void onCreate() {
        // setup OpenCV camera stuff
        // init mProcessing with mSurfaceView
    }
}

public class Processing extends Thread {
    private VideoCapture mCamera;
    private SurfaceView mSurfaceView;   // maybe just the SurfaceHolder
    Processing(VideoCapture camera, SurfaceView surfaceView) {
        mCamera = camera;
        mSurfaceView = surfaceView;
    }
    @Override
    public void run() {
        mCamera.grab();
        mCamera.retrieve(...);
        // process retrieved images
        // image to bitmap
        // What now, how to get bitmap to MainActivity? Passing using intent is a performace hit I guess
        // maybe something like if (mSurfaceView != null) { Canvas canvas = mSurfaceView.lockSurface(); ... }
    }
}

How would you design such application? Is there anything else I need to consider?

Upvotes: 3

Views: 787

Answers (1)

BCL
BCL

Reputation: 157

Ok, this is how I've done it: I've set the SurfaceView to either the correct view (if app is running) and to null if not (i.e. paused) in the onServiceConnected/onServiceDisconnected of MainActivity. In the service I check whether the view exists or not. It is not the nicest decoupling but it works and as far as I can tell right now the performance is Ok.

Upvotes: 1

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