Android 音量鍵增大減小捕捉

@Override
 public boolean onKeyDown(
   int keyCode, KeyEvent event) {
  // TODO Auto-generated method stub

  if (keyCode == KeyEvent.KEYCODE_VOLUME_UP) {

   Intent i = new Intent(
     Intent.ACTION_MAIN);

   i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

   i.addCategory(Intent.CATEGORY_HOME);

   startActivity(i);

   return true;
  }

  if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) {

   Toast.makeText(
     Bengkui.this,
     "彈出對話框", 1000)
     .show();
   Intent intent = new Intent(
     Bengkui.this,
     ShoujizhengrenActivity.class);
   startActivity(intent);

   return true;
  }

  else {
   return super.onKeyDown(
     keyCode, event);

  }

 }