title: seekBar thumb gets stretched when seekBar is clicked
body: <p>I'm experiencing a strange issue. In my app I have a custom <code>SeekBar</code> with a thumb that has 2 states. When I click the <code>seekBar</code>, its thumb gets distorted and <em>returns to its normal condition after a couple of seconds.</em> The corresponding <code>MediaPlayer</code> object reacts immediately as expected, the issue is just a visual one. Snapshots to illustrate this:</p>
  
  <p>Normal behavior:</p>
  
  <p><img src="https://i.stack.imgur.com/qWg6J.png" alt="enter image description here"></p>
  
  <p>When the <code>seekBar</code> is clicked:</p>
  
  <p><img src="https://i.stack.imgur.com/u9qCO.png" alt="enter image description here"></p>
  
  <p>I have no idea what is wrong about that. </p>
  
  <p>SeekBar:</p>
  
  <pre><code>     &lt;SeekBar
          android:id="@+id/seekBarMain"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_alignParentBottom="true"
          android:layout_alignParentLeft="true"
          android:layout_gravity="bottom"
          android:layout_marginBottom="5dp"
          android:indeterminate="false"
          android:maxHeight="3dp"
          android:maxWidth="450dp"
          android:minHeight="3dp"
          android:paddingLeft="9dp"
          android:paddingRight="9dp"
          android:progressDrawable="@drawable/pb"
          android:thumb="@drawable/thumb_state" /&gt;
  </code></pre>
  
  <p>Drawable used for its Thumb:</p>
  
  <pre><code>      &lt;?xml version="1.0" encoding="utf-8"?&gt;
         &lt;selector xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
  &lt;item android:drawable="@drawable/thumb_pressed" android:state_enabled="true" android:state_pressed="true"/&gt;
  &lt;item android:drawable="@drawable/thumb" android:state_pressed="false"/&gt;
  
        &lt;/selector&gt;
  </code></pre>
  
  <p>OnTouchListener:</p>
  
  <pre><code>        @Override
  public boolean onTouch(View v, MotionEvent event) {
  
      if (v.getId() == R.id.seekBarMain) {
  
          if (mp.isPlaying()) {
  
              int playPositionInMillisecconds = (mediaFileLengthInMilliseconds / 100)
                      * sb.getProgress();
              mp.seekTo(playPositionInMillisecconds);
          } else {
              int playPositionInMillisecconds = (mediaFileLengthInMilliseconds / 100)
                      * sb.getProgress();
              mp.start();
              mp.seekTo(playPositionInMillisecconds);
              btnPlay.setBackgroundResource(R.drawable.button_pause);
              primarySeekBarProgressUpdater();
  
          }
      }
  
      return false;
  
  }
  </code></pre>
  
  <p>Any ideas why that happens?</p>