Get Mat object from Camera frame Android for OpenCV

I am developing an android application based on Tutorial 2 given by OpenCV4Android. What I want to achieve is to get the Mat object of the camera frame when I touch the phone's screen (onTouch()). I want to modify the code such that I store the image as Mat instead of a jpeg file on the phone's memory. The Mat will then go under further processing.

Do I need to involve the onCameraFrame() function? Any guidance will be much appreciated. I am very new to Android developing and OpenCV as well.

Note: I am using Android version 4.2.2 and OpenCV2.4.8.

Edit:

After editing onTouch() and onCameraFrame() functions these are the code snippets:

public Mat onCameraFrame(CvCameraViewFrame inputFrame) {

        Mat img = inputFrame.rgba();

        if(touched) {
            int imgsize = (int) (img.total()*img.channels());
            byte[] data = new byte[imgsize];
            img.get(0,0,data);
            int col = img.cols();
            int row = img.rows();
            Toast.makeText(this, "size:"+imgsize+" row:"+row+" col:"+col, Toast.LENGTH_SHORT).show();

            StartSocket(row, col, imgsize, data);

            touched = false;
        }

        return img;
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        Log.i(TAG,"onTouch event"); 
        touched = true;
        return true;
    }

What I did is basically convert the Mat object into a ByteArray called data[] and send it to a server through a socket along with other information. The socket works fine as a separate project when i try to send text files, so I believe there is nothing wrong with it.

And I don't have the LogCat since I am running the app directly on my device.

if you want to process images from the camera, yes, you'll need the onCameraFrame() method, as it provides your image

public class MyActivity extends Activity implements CvCameraViewListener2,OnTouchListener {
    boolean touched=false;
    public boolean onTouch(View v, MotionEvent event) {
         touched = true;
         return true;
    }
    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
        Mat rgba = inputFrame.rgba();
        if ( touched ) {
            // do some processing on rgba Mat
            touched = false;
        }
        return rgba;
    }
}