title: How to setAlpha to android Button
body: <p>I have three buttons, sharing same background image, i want to disable button one of them by using Alpha.</p>
  
  <p>But when i am using the following code:</p>
  
  <pre><code> button1.getBackground().setAlpha(45);
  </code></pre>
  
  <p>it is changing the background for all three buttons. but i need for only one.
  can we done by using by Alpha()?? or some other things we can use so that button will looks in disabled mode.</p>