Draw interacting circle on canvas

I have to draw circle on screen and get interaction to it by OnTouch method. Kindly help me out. Here is the code that I have tried. Here the problem is that It does not intract with user interaction but this code successfully draw the circle

public class DrawingView extends View implements OnTouchListener {

static int x, y, r = 255, g = 255, b = 255;
final static int radius = 30;
Paint paint; // using this ,we can draw on canvas

public DrawingView(Context context) {
    super(context);
    paint = new Paint();
    paint.setAntiAlias(true); // for smooth rendering
    paint.setARGB(255, r, g, b); // setting the paint color

    // to make it focusable so that it will receive touch events properly
    setFocusable(true);

    // adding touch listener to this view
    this.setOnTouchListener(this);
}

// overriding the View's onDraw(..) method
public void onDraw(Canvas canvas) {
    paint.setARGB(255, r, g, b);

    super.onDraw(canvas);
    // drawing the circle

    canvas.drawCircle(x, y, radius, paint);
    randColor(); // calls this method to generate a color before drawing
    invalidate(); // calls onDraw method

}

// this is the interface method of "OnTouchListener"
public boolean onTouch(View view, MotionEvent event) {
    x = (int) event.getX() - (radius / 2); // some math logic to plot the
                                            // circle in exact touch place
    y = (int) event.getY() - (radius / 2);
    // System.out.println("X,Y:"+"x"+","+y); //see this output in "LogCat"
    randColor(); // calls this method to generate a color before drawing
    invalidate(); // calls onDraw method
    return true;
}

// this method sets a random color using Math.random()
// Note: RGB color values ranges from 0 to 255..
public void randColor() {
    r = (int) (Math.random() * 255);
    g = (int) (Math.random() * 255);
    b = (int) (Math.random() * 255);
    // Toast.makeText(c, "r,g,b="+r+","+g+","+b,Toast.LENGTH_SHORT).show();
}

} But the problem is that, it does not get user interaction