title: Change ImageView after few seconds
body: <p>I'm trying to implement a simple activity that will let user to insert a password.
  I've a gridview with the 9 images to use and 4 imageviews that will be the selected images (on clicking on item on gridview, the corresponding image will be filled with the selected one).</p>
  
  <p>Now the problem: I want that the 4 imageviews acts similar to password fields: for 1 seconds appears the selected item and then another image...
  I tried using asyncthread but I got and error: <strong>Only the original thread that created a view hierarchy can touch its views</strong> 
  Here my code:</p>
  
  <pre><code>@Override
  protected String doInBackground(ImageView... imageViews) {
      ImageView passField1 = imageViews[0];
      ImageView passField2 = imageViews[1];
      ImageView passField3 = imageViews[2];
      ImageView passField4 = imageViews[3];
      try {
          switch (currentField) {
          case 1:
              passField1.setImageResource(//selected recource on grid view);
              Thread.sleep(1000);
              passField1.setImageResource(R.drawable.e00); //this is a blank image
              break;
          case 2:
              passField2.setImageResource(//selected recource on grid view);
              Thread.sleep(1000);
              passField1.setImageResource(R.drawable.e00);
              break;
          case 3:
              passField3.setImageResource(//selected recource on grid view);
              Thread.sleep(1000);
              passField1.setImageResource(R.drawable.e00);
              break;
          case 4:
              passField4.setImageResource(//selected recource on grid view);
              Thread.sleep(1000);
              passField1.setImageResource(R.drawable.e00);
              break;
          }
      } catch (InterruptedException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }
  
      return null;
  }
  </code></pre>