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();
    }
   }
  }
 };
}