How to detect and process objects using Android and Opencv in real time

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I am developing and Android application using Opencv to detect the biggest contour, apply segmentation and compare each objects to a reference image but in real time. For now I have done the biggest contour detection using Canny edge detector, the segmentation using Canny and the objects matching using ORB but using static images. I tried a simple contour detection under onCameraFrame(), the time elapsed to process is 0.004 seconds but the drawn contour keeps changing so I can't perform segmentation and image matching on a false contour noting that this program will be used in industrial chain . Here is the ddetection code:

long e1 = Core.getTickCount();
    Mat mGray = new Mat();
    Imgproc.cvtColor(origMat, mGray, Imgproc.COLOR_BGR2GRAY);
    Imgproc.GaussianBlur(mGray, mGray, new Size(5, 5), 5);
    Imgproc.Canny(mGray, mGray, 50, 150, 3, false);
    Mat kernell = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(9,9));
    Imgproc.morphologyEx(mGray, mGray, Imgproc.MORPH_CLOSE, kernell);

    List<MatOfPoint> contours = new ArrayList<MatOfPoint>();
    Mat hierarchy = new Mat();
    Imgproc.findContours(mGray, contours, hierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);
    MatOfPoint2f approxCurve = new MatOfPoint2f();

    for (int idx = 0; idx < contours.size() ; idx++) {
        MatOfPoint2f contour2f = new MatOfPoint2f( contours.get(idx).toArray() );
        //Processing on mMOP2f1 which is in type MatOfPoint2f
        double approxDistance = Imgproc.arcLength(contour2f, true)*0.02;
        Imgproc.approxPolyDP(contour2f, approxCurve, approxDistance, true);

        //Convert back to MatOfPoint
        MatOfPoint points = new MatOfPoint( approxCurve.toArray() );

        // Get bounding rect of contour
        Rect rect = Imgproc.boundingRect(points);

        // draw enclosing rectangle (all same color, but you could use variable i to make them unique)
        Imgproc.rectangle(origMat, rect.tl(), rect.br(), new Scalar(0, 255, 0));
    }

    long e2 = Core.getTickCount();

    long e = e2 - e1;
    double time = e / Core.getTickFrequency();

    Toast.makeText(this, "" + time, Toast.LENGTH_LONG).show();