Android app Force closed by memory leak

edit

i'd rather make all temporary Mat's class members, and allocate them only once.

public class MyActivity extends Activity implements CvCameraViewListener2 {
    CameraBridgeViewBase mOpenCvCameraView;
    Mat mRgba, mGray, mHsv;
   ...
}

public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
    Mat rgba = inputFrame.rgba();
    // convert to hsv, get binary img:
    Imgproc.cvtColor(rgba , mHsv, Imgproc.COLOR_BGR2HSV);
    Core.inRange(mHsv, new Scalar(50, 70, 100), new Scalar(150, 250, 250), mGray);

    // save a rgba copy of the binary for drawing later: 
    Imgproc.cvtColor(mGray , mRgba, Imgproc.COLOR_GRAY2RGBA);
    // can do Canny in-place:
    Imgproc.Canny(mGray, mGray, 80, 100, 5, true);
    // now, we *need* a new here !
    Mat lines = new Mat();
    Imgproc.HoughLinesP(mGray, lines, 1, Math.PI/180, 125, 20, 20);
    for (int x = 0; x < lines.cols(); x++) 
    {
          double[] vec = lines.get(0, x);
          double x1 = vec[0], 
                 y1 = vec[1],
                 x2 = vec[2],
                 y2 = vec[3];
          Point start = new Point(x1, y1);
          Point end = new Point(x2, y2);

          Core.line(mRgba, start, end, new Scalar(255,0,0), 2); 
    }
    lines.release(); // !!
    return mRgba;
}

public void onCameraViewStarted(int width, int height) {
    // allocate the temporary Mat's only once:
    mGray = new Mat(height,width,CvType.CV_8U);
    mHsv = new Mat(height,width,CvType.CV_8UC3);
    mRgba = new Mat(height,width,CvType.CV_8UC4);
}

Make sure there's no any Mat describing method in onCameraFrame function. I assume it's because in every frame operation it creates new Mat without closing previous and forces to a memory leak. (didnt try to code, but having similar issue is solved this method)

public class ... {

  Mat sourceimage, mRgba, lines, filter2;

  public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
    sourceimage = inputFrame.rgba();
    Imgproc.cvtColor(sourceimage , sourceimage, Imgproc.COLOR_RGBA2RGB);
    Imgproc.cvtColor(sourceimage , sourceimage, Imgproc.COLOR_BGR2HSV);

    mRgba = new Mat();
    lines = new Mat();
    filter2= new Mat();

    Core.inRange(sourceimage, new Scalar(50, 70, 100), new Scalar(150, 250, 250), filter2);
    mRgba=filter2.clone();

    Imgproc.cvtColor(mRgba , mRgba, Imgproc.COLOR_GRAY2RGBA);
    Imgproc.Canny(filter2, filter2, 80, 100, 5, true);
    Imgproc.HoughLinesP(filter2, lines, 1, Math.PI/180, 125, 20, 20);
    for (int x = 0; x < lines.cols(); x++) 
    {
          double[] vec = lines.get(0, x);
          double x1 = vec[0], 
                 y1 = vec[1],
                 x2 = vec[2],
                 y2 = vec[3];
          Point start = new Point(x1, y1);
          Point end = new Point(x2, y2);

          Core.line(mRgba, start, end, new Scalar(255,0,0), 2); 
    }
    return mRgba;
  }
}

Your problem is caused by explicitly stating the new operator. If you do so than the garbage collector will not automatically delete your objects once they run out of scope. You can avoid this by changing your code to:

public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
    Mat sourceimage = inputFrame.rgba();
    Imgproc.cvtColor(sourceimage , sourceimage, Imgproc.COLOR_RGBA2RGB);
    Imgproc.cvtColor(sourceimage , sourceimage, Imgproc.COLOR_BGR2HSV);

    Mat mRgba, lines, filter2;

    Core.inRange(sourceimage, new Scalar(50, 70, 100), new Scalar(150, 250, 250), filter2);
    mRgba=filter2.clone();

    Imgproc.cvtColor(mRgba , mRgba, Imgproc.COLOR_GRAY2RGBA);
    Imgproc.Canny(filter2, filter2, 80, 100, 5, true);
    Imgproc.HoughLinesP(filter2, lines, 1, Math.PI/180, 125, 20, 20);
    for (int x = 0; x < lines.cols(); x++) 
    {
          double[] vec = lines.get(0, x);
          double x1 = vec[0], 
                 y1 = vec[1],
                 x2 = vec[2],
                 y2 = vec[3];
          Point start (x1, y1);
          Point end (x2, y2);

          Core.line(mRgba, start, end, new Scalar(255,0,0), 2); 
    }
    return mRgba;
}

And the memory leaking should be a thing of the past. Other way is to explicitly delete every object yourself!