title: how to control mediaplayer volume
body: <p>I created a simple application.
  In my main activity class i use this to play a sound when a button is clicked</p>
  
  <pre><code>MediaPlayer buttonSound = MediaPlayer.create(this, R.drawable.button_sound); 
  
  public void onClick(View arg0){
                  buttonSound.start();
                               }
  </code></pre>
  
  <p>In my main activity class i have a service that start a background music</p>
  
  <pre><code> Intent svc=new Intent(this, BackgroundSoundService.class);
   startService(svc);
  </code></pre>
  
  <p>The problem is that I can't handle them (my background music and my button sound) with the volume buttons of my mobile.
  If i decrease the volume of my mobile, my application volume doesn't change!
  what should I do?</p>