title: draw circle on a image with canvas and event Touch
body: <p>I'm making an app which paints a circle with a Touch event on the screen. The next code works fine:</p>
  <pre><code> Class Punto extends view{
     Paint paint;
     Point point = new Point();
  
   Public Punto(Context contex){
   super(context);
   }
  
   @Override
   protected void onDraw(Canvas canvas){
              super.onDraw(canvas);              
              paint.setColor(Color.BLUE);
              canvas.drawCircle(point.x,point.y,10,paint);
              }
  
   @Override
   public boolean onTouchEvent (MotionEvent event) {
          switch (event.getAction()) {
              case MotionEvent.ACTION_DOWN :
                  point.x = event.getX();
                  point.y = event.getY();
                  break;
          }
          return true;
      }
  
  class Point{
     float x,y;
   }
  </code></pre>
  <p>Activity:</p>
  <pre><code>public class Pintar extends Activity {
   
  @Override
  public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     Punto punto = new Punto(this);
     setContentView(punto);
  }
  </code></pre>
  <p>However I need that the circle be painted on a picture (in my case is a market's plane) but I don't know how I can do this.</p>