播放一段音乐

private void playTone() {
// 上班时间到了，响铃并显示“可以下班啦！”
Uri uri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
mRingtone = RingtoneManager.getRingtone(MainActivity.this, uri);
mRingtone.play();
}

@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
unregisterReceiver(mTimeReceiver);
if (mRingtone != null && mRingtone.isPlaying()) {
mRingtone.stop();
}
}