Android 进程间通信实现原理分析

package pandafang.demo.playerserver;
interface IRemoteService {
 void play();
 void stop();
}

/**
 * 播放音乐的服务
 */
public class PlayerService extends Service {

 public static final String TAG = "PlayerService";

 private MediaPlayer mplayer;

 @Override
 public IBinder onBind(Intent intent) {
  Log.i(TAG,"service onbind");
  if(mplayer==null){
   // 方法一说明
   // 此方法实例化播放器的同时指定音乐数据源 ,若用此方法在，mplayer.start() 之前不需再调用mplayer.prepare()
   // 官方文档有说明 ：On success, prepare() will already have been called and must not be called again.
   // 译文：一旦create成功，prepare已被调用，勿再调用 。查看源代码可知create方法内部已经调用prepare方法。
   // 方法一开始
   // mplayer = MediaPlayer.create(this, R.raw.lost);
   // 方法一结束

   // 方法二说明
   // 若用此方法，在mplayer.start() 之前需要调用mplayer.prepare()
   // 方法二开始
   mplayer = new MediaPlayer();
   try {
    FileDescriptor fd = getResources().openRawResourceFd(R.raw.lost).getFileDescriptor(); // 获取音乐数据源
    mplayer.setDataSource(fd); // 设置数据源
    mplayer.setLooping(true); // 设为循环播放
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
   // 方法二结束
   Log.i(TAG,"player created");
  }
  return mBinder;
 }

 // 实现aidl文件中定义的接口
 private IBinder mBinder = new IRemoteService.Stub() {

  @Override
  public void stop() throws RemoteException {
   try {
    if (mplayer.isPlaying()) {
     mplayer.stop();
    }
   } catch (Exception e) {
    // TODO: handle exception
    e.printStackTrace();
   }
  }

  @Override
  public void play() throws RemoteException {
   try {
    if (mplayer.isPlaying()) {
     return;
    }
    // start之前需要prepare。
    // 如果前面实例化mplayer时使用方法一，则第一次play的时候直接start，不用prepare。
    // 但是stop一次之后,再次play就需要在start之前prepare了。
    // 前面使用方法二 这里就简便了， 不用判断各种状况
    mplayer.prepare();
    mplayer.start();
   } catch (Exception e) {
    // TODO: handle exception
    e.printStackTrace();
   }
  }
 };
 @Override
 public boolean onUnbind(Intent intent) {
  if (mplayer != null) {
   mplayer.release();
  }
  Log.i(TAG,"service onUnbind");
  return super.onUnbind(intent);
 }
}

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="pandafang.demo.playerserver"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <service android:name=".PlayerService" android:process=":remote">
            <intent-filter >
                <action android:name="com.example.playerserver.PlayerService"/>
            </intent-filter>
         </service>
    </application>
</manifest>

/**
 * 客户端控制界面
 */
public class MainActivity extends Activity {

 public static final String TAG = "MainActivity";

 // 服务端 AndroidManifest.xml中的intent-filter action声明的字符串
 public static final String ACTION = "com.example.playerserver.PlayerService";

 private Button playbtn, stopbtn;

 private IRemoteService mService;

 private boolean isBinded = false;

 private ServiceConnection conn = new ServiceConnection() {

  @Override
  public void onServiceDisconnected(ComponentName name) {
   isBinded = false;
   mService = null;
  }

  @Override
  public void onServiceConnected(ComponentName name, IBinder service) {
   mService = IRemoteService.Stub.asInterface(service);
   isBinded = true;
  }
 };
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        doBind();
        initViews();
    }
    private void initViews() {
     playbtn = (Button) findViewById(R.id.button1);
        stopbtn = (Button) findViewById(R.id.button2);
        playbtn.setOnClickListener(clickListener);
        stopbtn.setOnClickListener(clickListener);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    @Override
    protected void onDestroy() {
  doUnbind();
     super.onDestroy();
    }
    public void doBind() {
     Intent intent = new Intent(ACTION);
     bindService(intent, conn, Context.BIND_AUTO_CREATE);
    }
    public void doUnbind() {
     if (isBinded) {
      unbindService(conn);
         mService = null;
         isBinded = false;
     }

    }
    private OnClickListener clickListener = new OnClickListener() {

  @Override
  public void onClick(View v) {
   if (v.getId() == playbtn.getId()) {
    // play
    Log.i(TAG,"play button clicked");
    try {
     mService.play();
    } catch (RemoteException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   } else {
    // stop
    Log.i(TAG,"stop button clicked");
    try {
     mService.stop();
    } catch (RemoteException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   }
  }
 };
}