title: clearColorFilter() don't work on android 2.3
body: <p>i'm using setColorFilter to color some button... the code is this:</p>
  
  <pre><code>    final Button falso = (Button) findViewById(R.id.falso);
      final Button vero = (Button) findViewById(R.id.vero);
  
  
      vero.setOnClickListener(new OnClickListener() {         
          public void onClick(View v) {
              vero.getBackground().setColorFilter(new LightingColorFilter(0x00000000, 0x00FF0FF));    
              falso.getBackground().clearColorFilter();
              esame.set("V");
          }
      });
  
  
      falso.setOnClickListener(new OnClickListener() {            
          public void onClick(View v) {
              falso.getBackground().setColorFilter(new LightingColorFilter(0x00000000, 0x00FF0FF));
              vero.getBackground().clearColorFilter(); 
              esame.set("F");
          }
      });
  </code></pre>
  
  <p>when i click the button "vero" i want reset the colour of "falso" and viceversa.
  i tried this code on android ics and all work good, but when i tried it on android 2.3 i have a bad surprise.</p>
  
  <p>when i click the button the colour don't reset and i don't understand why.</p>