android之Service学习——音乐播放器

那个，网上关于Service的例子似乎大多都是音乐播放器哦，呵，俺也是参照着练习了一下

 

 第一步:候改main.xml布局文件（我这里增加了四个按钮，上一首，播放，下一首，暂停)代码如下:

<?xml version="1.0" encoding="utf-8"?><RelativeLayoutandroid:id="@+id/widget38"android:layout_width="fill_parent"android:layout_height="fill_parent"xmlns:android="http://schemas.android.com/apk/res/android"><Buttonandroid:id="@+id/button4"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="暂停"android:textSize="20sp"android:textStyle="bold"android:layout_alignTop="@+id/button3"ndroid:layout_toRightOf="@+id/button3"></Button><Buttonandroid:id="@+id/button3"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="下一首"android:textSize="20sp"android:textStyle="bold"android:layout_alignTop="@+id/button2"android:layout_toRightOf="@+id/button2"></Button><Buttonandroid:id="@+id/button2"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="播放"android:textSize="20sp"android:textStyle="bold"android:layout_alignTop="@+id/button1"android:layout_toRightOf="@+id/button1"></Button><Buttonandroid:id="@+id/button1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="上一首"android:textSize="20sp"android:textStyle="bold"android:layout_centerVertical="true"android:layout_alignParentLeft="true"></Button></RelativeLayout>

第二步:新建一个MyService.java类，播放音乐都是在这个类里进行,代码如下:

public class MyService extends Service {private MediaPlayer mMediaPlayer;private Cursor mCursor;private int mPlayPosition = 0;String[] projection = new String[] {"audio._id AS _id", // index must match IDCOLIDX belowMediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media.ALBUM,MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.DATA,MediaStore.Audio.Media.MIME_TYPE, MediaStore.Audio.Media.ALBUM_ID,MediaStore.Audio.Media.ARTIST_ID, MediaStore.Audio.Media.DURATION};public static final String PLAY_ACTION = "com.csq.ServiceTest.PLAY_ACTION";public static final String PAUSE_ACTION = "com.csq.ServiceTest.PAUSE_ACTION";public static final String NEXT_ACTION = "com.csq.ServiceTest.NEXT_ACTION";public static final String PREVIOUS_ACTION = "com.csq.ServiceTest.PREVIOUS_ACTION";//创建时，系统调用public void onCreate() {Log.i("Service", "onCreate");super.onCreate();mMediaPlayer = new MediaPlayer();//通过一个URI可以获取所有音频文件Uri MUSIC_URI = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;//默认大于10秒的看作是歌mCursor = getContentResolver().query(MUSIC_URI, projection, "duration>10000", null, null);}//必须实现的一个方法，返回一个绑定的接口给Service//可以方法null，通常返回一个有AIDL定义的接口public IBinder onBind(Intent arg0) {Log.i("Service", "onBind");return null;}//2.0以后用该方法替代onStart方法，在创建Service后也就是onCreate后调用，创建一次以后每次启动该服务都直接调用onStartCommand//如果只希望提供绑定，则不需要实现该方法public int onStartCommand(Intent intent, int flags, int startId) {Log.i("Service", "onStartCommand");String action = intent.getAction();if(action.equals(PLAY_ACTION)){play();}else if(action.equals(PAUSE_ACTION)){pause();}else if(action.equals(NEXT_ACTION)){next();}else if(action.equals(PREVIOUS_ACTION)){previous();}return super.onStartCommand(intent, flags, startId);}//当Service不再启动时，系统调用public void onDestroy() {Log.i("Service", "onDestroy");mMediaPlayer.release();super.onDestroy();}public void inite() {mMediaPlayer.reset();String dataSource = getDateByPosition(mCursor, mPlayPosition);String info = getInfoByPosition(mCursor, mPlayPosition);//用Toast显示歌曲信息Toast.makeText(getApplicationContext(), info, Toast.LENGTH_SHORT).show();try {mMediaPlayer.setDataSource(dataSource);mMediaPlayer.prepare();mMediaPlayer.start();} catch (IllegalArgumentException e1) {e1.printStackTrace();} catch (IllegalStateException e1) {e1.printStackTrace();} catch (IOException e1) {e1.printStackTrace();}}//play the musicpublic void play() {inite();}//暂停时，结束服务public void pause() {stopSelf();}//上一首public void previous() {if (mPlayPosition == 0) {mPlayPosition = mCursor.getCount() - 1;} else {mPlayPosition--;}inite();}//下一首public void next() {if (mPlayPosition == mCursor.getCount() - 1) {mPlayPosition = 0;}else {mPlayPosition++;}inite();}//根据位置来获取歌曲位置public String getDateByPosition(Cursor c,int position){c.moveToPosition(position);int dataColumn = c.getColumnIndex(MediaStore.Audio.Media.DATA);String data = c.getString(dataColumn);return data;}//获取当前播放歌曲演唱者及歌名public String getInfoByPosition(Cursor c,int position){c.moveToPosition(position);int titleColumn = c.getColumnIndex(MediaStore.Audio.Media.TITLE);int artistColumn = c.getColumnIndex(MediaStore.Audio.Media.ARTIST);String info = c.getString(artistColumn)+" " + c.getString(titleColumn);return info;}}

 

第三步:修改MainActivity.java代码如下:

public class MainActivity extends Activity implements OnClickListener{private Button mPrevious,mPlay,mNext,mPause;private ComponentName component;    public void onCreate(Bundle savedInstanceState)     {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                component = new ComponentName(this,MyService.class);                mPrevious = (Button)findViewById(R.id.button1);    mPlay = (Button)findViewById(R.id.button2);    mNext = (Button)findViewById(R.id.button3);    mPause = (Button)findViewById(R.id.button4);    mPrevious.setOnClickListener(this);    mPlay.setOnClickListener(this);    mNext.setOnClickListener(this);    mPause.setOnClickListener(this);    }public void onClick(View v) {if(v == mPrevious){Intent mIntent = new Intent(MyService.PREVIOUS_ACTION);mIntent.setComponent(component);startService(mIntent);}else if(v == mPlay){Intent mIntent = new Intent(MyService.PLAY_ACTION);mIntent.setComponent(component);startService(mIntent);}else if(v == mNext){Intent mIntent = new Intent(MyService.NEXT_ACTION);mIntent.setComponent(component);startService(mIntent);}else{Intent mIntent = new Intent(MyService.PAUSE_ACTION);mIntent.setComponent(component);startService(mIntent);}}}

第四步：修改AndroidManifest.xml，这里只是把我们的MyService申明进去

<service android:name=".MyService"/>