JamesMusic浅读--------8，音乐文件播放

设置ListView的onItemClick函数为

private AdapterView.OnItemClickListener onItemClickListener = new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Log.i(TAG, "on click"+ position);
mApp.getPlaybackKickstarter().initPlayback(mContext,mQuerySelection,Common.PLAY_ALL_SONGS,
position, true , false);
}
};

这个函数调用initPlayback，这个函数根据界面情况，启动播放界面，或者后台音播放服务没开启的话，开启服务。这里先实现开启服务



public void initPlayback(Context context,
String querySelection,
int playbackRouteId,
int currentSongIndex,
boolean showNowPlayingActivity,
boolean playAll) {

mApp = (Common) mContext.getApplicationContext();
mQuerySelection = querySelection;
mPlaybackRouteId = playbackRouteId;
mCurrentSongIndex = currentSongIndex;

// TODO: 2016/6/2
startService();

if(showNowPlayingActivity){

}else {

}
}
/**
* Starts AudioPlaybackService. Once the service is running, we get a
* callback to onServiceRunning() (see below). That's where the method to
* build the cursor is called.
*/
private void startService() {
Intent intent = new Intent(mContext, AudioPlaybackService.class);
mContext.startService(intent);
}

这儿启动AudioPlaybackService类

public class AudioPlaybackService extends Service {
//Context and Intent.
private Context mContext;
private Service mService;

//Global Objects Provider.
private Common mApp;
//MediaPlayer objects and flags.
private MediaPlayer mMediaPlayer;
private MediaPlayer mMediaPlayer2;
private int mCurrentMediaPlayer = 1;
private boolean mFirstRun = true;

//Handler object.
private Handler mHandler;
//AudioManager.
private AudioManager mAudioManager;

/**
* Constructor that should be used whenever this
* service is being explictly created.
*
* @param context The context being passed in.
*/
public AudioPlaybackService(Context context) {
mContext = context;
}

/**
* Empty constructor. Required if a custom constructor
* was explicitly declared (see above).
*/
public AudioPlaybackService() {
super();
}

/**
* Prepares the MediaPlayer objects for first use
* and starts the service. The workflow of the entire
* service starts here.
*
* @param intent  Calling intent.
* @param flags   Service flags.
* @param startId Service start ID.
*/
@SuppressLint("NewApi")
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
super.onStartCommand(intent, flags, startId);

//Context.
mContext = getApplicationContext();
mService = this;
mHandler = new Handler();

mApp = (Common) getApplicationContext();
mApp.setService((AudioPlaybackService) this);
mAudioManager = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);

initMediaPlayers();
prepareMediaPlayer(0);
return START_STICKY;
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}

private void initMediaPlayers() {

if (mMediaPlayer != null) {
mMediaPlayer.release();
mMediaPlayer = null;
}

if (mMediaPlayer2 != null) {
// TODO: 2016/6/3
}

mMediaPlayer = new MediaPlayer();

setCurrentMediaPlayer(1);

getMediaPlayer().reset();

// TODO: 2016/6/3
getMediaPlayer().setLooping(true);
try {
getMediaPlayer().setWakeMode(mContext, PowerManager.PARTIAL_WAKE_LOCK);
} catch (Exception e) {
mMediaPlayer = new MediaPlayer();
setCurrentMediaPlayer(1);
}

mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);

}

private void setCurrentMediaPlayer(int currentMediaPlayer) {
mCurrentMediaPlayer = currentMediaPlayer;
}

public MediaPlayer getMediaPlayer() {

return mMediaPlayer;
}

// TODO: 2016/6/3

/**
* Grabs the song parameters at the specified index, retrieves its
* data source, and beings to asynchronously prepare mMediaPlayer.
* Once mMediaPlayer is prepared, mediaPlayerPrepared is called.
*
* @return True if the method completed with no exceptions. False, otherwise.
*/
public boolean prepareMediaPlayer(int songIndex) {
try{
mMediaPlayer.reset();
mMediaPlayer.setDataSource("/storage/emulated/0/Music/Goldberg_Variations.mp3");
mMediaPlayer.prepare();
mMediaPlayer.start();

}catch (Exception e){
e.printStackTrace();
}
return  true;
}
}

这儿的onStartCommand函数里面调用preparMediaPlayer函数，这个函数我们先简单的让它播放音乐。这和源项目不一样，稍后我们去改。
现在试试吧。可以放音乐了。