title: onTouchEvent() callback does not work
body: <p>I am developing <strong>Android 2.1 API 7</strong> app.</p>
  
  <p>In my Activity, I add the <code>onTouchEvent()</code> callback to handle <strong>screen touch</strong> event:</p>
  
  <pre><code>public class MyActivity extends Activity{
  
     ...
  
     @Override
      public boolean onTouchEvent(MotionEvent event) {
          if (event.getAction() == MotionEvent.ACTION_DOWN) {
              //Did something here
              Log.v("TOUCH SCREEN", "test");
          }
  
          return super.onTouchEvent(event);
      }
  }
  </code></pre>
  
  <p>I test this on a real device, but when I touch the screen, it seems the callback is not invoked, because I did not see the <code>Log.v(...)</code> information. Why??</p>