播放一个声音

 // Do the common stuff when starting the alarm.    private void startAlarm(MediaPlayer player)            throws java.io.IOException, IllegalArgumentException,                   IllegalStateException {        final AudioManager audioManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE);        // do not play alarms if stream volume is 0        // (typically because ringer mode is silent).        if (audioManager.getStreamVolume(AudioManager.STREAM_ALARM) != 0) {            player.setAudioStreamType(AudioManager.STREAM_ALARM);            player.setLooping(true);            player.prepare();            player.start();        }    }    private void setDataSourceFromResource(Resources resources,            MediaPlayer player, int res) throws java.io.IOException {        AssetFileDescriptor afd = resources.openRawResourceFd(res);        if (afd != null) {            player.setDataSource(afd.getFileDescriptor(), afd.getStartOffset(),                    afd.getLength());            afd.close();        }    }private static final float IN_CALL_VOLUME = 0.125f; // Check if we are in a call. If we are, use the in-call alarm                // resource at a low volume to not disrupt the call.                if (mTelephonyManager.getCallState()                        != TelephonyManager.CALL_STATE_IDLE) {                    Log.v("Using the in-call alarm");                    mMediaPlayer.setVolume(IN_CALL_VOLUME, IN_CALL_VOLUME);                    setDataSourceFromResource(getResources(), mMediaPlayer,                            R.raw.in_call_alarm);                } else {                    mMediaPlayer.setDataSource(this, alert);                }                startAlarm(mMediaPlayer);

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