title: Android - make seekbar invisible but still functional
body: <p>I want to have the effect of a SeekBar but I don't want it to be visible. I want the user to slide their finger left and right over an image to decrease/increase opacity of an image. I have this working with a SeekBar, setting the alpha of the image as progress on the SeekBar changes. The challenge now is to hide the SeekBar. I just want the user to move their finger over the image back and forth and it change the opacity. </p>
  
  <p>I have tried:</p>
  
  <pre><code>final SeekBar opacitySeekBar = (SeekBar) myLayout.findViewById(R.id.opacitySeekBar);
  opacitySeekBar.setAlpha(0);
  </code></pre>
  
  <p>also:</p>
  
  <pre><code>opacitySeekBar.setVisibility(View.INVISIBLE);
  </code></pre>
  
  <p>and neither worked. Any ideas?</p>