title: Android apply animation to button background
body: <p>I have a button which currently has an animation assigned to it on click:</p>
  
  <pre><code>Button btn = (Button)findViewById(R.id.btn);
  btn.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) {
          v.startAnimation(animRotate);
  }
  });
  </code></pre>
  
  <p>Here is an example of the button in XML:</p>
  
  <pre><code>&lt;Button
      android:id="@+id/btn"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:background="@android:color/transparent"
      android:text="@string/btnText"
      android:textColor="#ffffff"
      android:textSize="18dp"
      android:padding="12dp"
      android:drawableTop="@drawable/btnIcon"
      android:layout_weight="1" /&gt;
  </code></pre>
  
  <p>The animation works spot on, however on the button itself there is a text value and a drawable value, and I would like to be able to target the drawable and animate that only. I have searched all over the net and everything appears to be targeting objects by their id without any background/drawable selection.</p>
  
  <p>Any feedback is welcome, even if its just to inform me that it can't be done.</p>
  
  <p>Many thanks.</p>