title: How to add gesture recognizer to a UIImageview?
body: <p>In the project, there are an <code>UIView</code> myView and an <code>UIImageView</code> myImage behinds the myView, views hierarchy:</p>
  
  <p>UIWindow<br/>
  |-- UIImageView (myImage)<br/>
  |-- UIView (myView) [whole screen]</p>
  
  <p>Then added a gesture recognizer to myImage in ViewController</p>
  
  <pre><code>UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleTap:)];
          tapGesture.numberOfTapsRequired = 1;
          [myImage addGestureRecognizer:tapGesture];
  </code></pre>
  
  <p>But gesture doesn't affect myImage, myImage has <code>setUserInteractionEnabled:YES</code>. It will only affect when myImage placed in front of myView, how can I solve this problem?</p>