在下文中我们实现的简单的音乐播放功能。
原创：Android应用开发记录-Andorid歌词秀（2）先来一个音频播放器
但是这样的方式在程序退出后播放也会停止，为了解决这个问题，使用的Service类。
在参考网上播放器例子代码的基础上，运用Proxy模式简化的Service的管理和使用。
功能简介：
1.选择手机上的音频，以list形式表示。
2.点击对应标题播放歌曲。
3.点击播放中的歌曲时，暂停播放，再次点击，继续播放。
简单说明
MusicPlaybackService 类
管理MediaPlayer 的生成和创建
实现了Resume功能
播放文件名的设定和取得功能
public class MusicPlaybackService extends Service {
private MediaPlayer mMediaPlayer = new MediaPlayer();
private final IBinder mBinder = new LocalBinder();
private int mPausePosition = 0;
private String mDataSource;
public class LocalBinder extends Binder {
public MusicPlaybackService getService() {
return MusicPlaybackService.this ;
}
}
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
@Override
public void onCreate() {
mMediaPlayer = new MediaPlayer();
super.onCreate();
}
@Override
public void onDestroy() {
mMediaPlayer.release();
mMediaPlayer = null;
super.onDestroy();
}
public void setDataSource(String path) {
mDataSource = path;
try{
mMediaPlayer.reset();
mMediaPlayer.setDataSource(path);
mMediaPlayer.prepare();
}catch(IOException e) {
return;
} catch (IllegalArgumentException e) {
return;
}
}
public String getDataSource(){
return mDataSource;
}
public void start() {
mMediaPlayer.start();
}
public void stop() {
mMediaPlayer.stop();
}
public void pause() {
mPausePosition = getPosition();
mMediaPlayer.pause();
}
public void resume() {
seek(mPausePosition);
mMediaPlayer.start();
}
public boolean isPlaying() {
return mMediaPlayer.isPlaying();
}
public int getDuration() {
return mMediaPlayer.getDuration();
}
public int getPosition() {
return mMediaPlayer.getCurrentPosition();
}
public long seek(long whereto) {
mMediaPlayer.seekTo((int ) whereto);
return whereto;
}
}
Service类完成以后，就可以使用的，只是还有点繁琐，能不能包装一下呢？在这个程序中为了简化Service的利用，追加了一个MusicPlaybackServiceProxy类
主要是封装的ServiceConnection关联部分。虽然mPlaybackService 是在绑定后（实际上还要晚一点）才可用的，但是MusicPlaybackServiceProxy随时可用。
代码其实很简单，一看就应该能理解。
public class MusicPlaybackServiceProxy {
private ContextWrapper mContextWrapper= null;
private MusicPlaybackService mPlaybackService = null ;
private ServiceConnection mPlaybackConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
mPlaybackService = ((MusicPlaybackService.LocalBinder)service).getService();
}
public void onServiceDisconnected(ComponentName className) {
mPlaybackService = null ;
}
};
MusicPlaybackServiceProxy(ContextWrapper cw){
mContextWrapper = cw;
}
void startAndBindService(){
mContextWrapper.startService(new Intent(mContextWrapper ,MusicPlaybackService.class));
mContextWrapper.bindService(new Intent(mContextWrapper, MusicPlaybackService.class), mPlaybackConnection, Context.BIND_AUTO_CREATE);
}
void stopService(){
if(mPlaybackService != null){
mContextWrapper.stopService(new Intent(mContextWrapper ,MusicPlaybackService.class));
}
}
public void setDataSource(String path) {
mPlaybackService.setDataSource(path);
}
public String getDataSource(){
if(mPlaybackService != null){
return mPlaybackService.getDataSource();
}else{
return null;
}
}
public void start() {
if(mPlaybackService != null){
mPlaybackService.start();
}
}
public void stop(){
if(mPlaybackService != null){
mPlaybackService.stop();
}
}
public void pause() {
if(mPlaybackService != null){
mPlaybackService.pause();
}
}
public void resume() {
if(mPlaybackService != null){
mPlaybackService.start();
}
}
public boolean isPlaying() {
if(mPlaybackService != null){
return mPlaybackService.isPlaying();
}else{
return false;
}
}
public int getDuration() {
if(mPlaybackService != null){
return mPlaybackService.getDuration();
}else{
return 0;
}
}
public int getPosition() {
if(mPlaybackService != null){
return mPlaybackService.getPosition();
}else{
return 0;
}
}
public long seek(long whereto) {
if(mPlaybackService != null){
return mPlaybackService.seek(whereto);
}else{
return 0;
}
}
};
最后是使用代码的例子，更简单。
public class SubtitleMain extends Activity{
private Cursor mCursor;
private ListView mFilelist;
private MusicPlaybackServiceProxy mProxy = new MusicPlaybackServiceProxy(this);
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mProxy.startAndBindService();
mCursor = getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null ,
null ,null, MediaStore.Audio.Media.DEFAULT_SORT_ORDER);
//初始化歌曲列表
mFilelist = (ListView)findViewById(R.id.audio_file_view);
startManagingCursor(mCursor);
String[] from = new String[] {MediaStore.Audio.Media.TITLE};
int[] to = new int[]{R.id.music_title};
SimpleCursorAdapter adapter =
new SimpleCursorAdapter(this,R.layout.file_list_row, mCursor, from ,to);
mFilelist.setAdapter(adapter);
mFilelist.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
mCursor.moveToPosition(position);
String url = mCursor.getString(mCursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA));
String urlPlaying = mProxy.getDataSource();
if(urlPlaying == null || url.compareTo(urlPlaying)!=0){
//如果是第一次播放或不是同一首歌
mProxy.setDataSource(url);
mProxy.start();
}else{
if(mProxy.isPlaying()){
mProxy.pause();
}else{
mProxy.resume();
}
}
}
});
}
@Override
protected void onPause() {
if(!mProxy.isPlaying()){
mProxy.stopService();
}
super.onPause();
}
}
