Android Bound Service实现方法详解

Android中的service是运行在后台的组件，如果其他组件（比如Activity）需要与后台的service交互，有以下三个途径：

一，若参与交互的Service，Activity运行在一个进程中（可简单理解为同一个APP中）。

那么只需要在Service的onBind方法中返回一个你自己实现的Binder对象（这个Binder类是service的内部类），然后就可以通过这个Binder对象与service交互，比如说可以在Binder类中实现一个方法将Service对象引用直接返回，从而可以让Activity直接调用Service的public方法，实例关键代码如下：

Activity端代码：

import com.example.startservicetest.MainService.LocalBinder;public class MainActivity extends ActionBarActivity implements OnClickListener{private Button btn_bind_in_same_service;private ServiceConnection conn = new ServiceConnection() {@Overridepublic void onServiceDisconnected(ComponentName name) {// TODO Auto-generated method stub}@Overridepublic void onServiceConnected(ComponentName name, IBinder service) {// TODO Auto-generated method stubLocalBinder binder = (LocalBinder)service;MainService mainService = binder.getService();String res = mainService.getString();Log.i("dazhou", "bind service result:"+res);}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);btn_bind_in_same_service = (Button)findViewById(R.id.btn_bind_service_in_same_app);btn_bind_in_same_service.setOnClickListener(this);}@Overridepublic void onClick(View v) {// TODO Auto-generated method stubint id = v.getId();Intent intent;switch (id) {case R.id.btn_bind_service_in_same_app:Log.i("dazhou", "bind service in same app");intent = new Intent(this, MainService.class);bindService(intent, conn, Context.BIND_AUTO_CREATE);break;default:break;}}}

Service端代码：

public class MainService extends Service {private LocalBinder mBinder = new LocalBinder();@Overridepublic IBinder onBind(Intent intent) {// TODO Auto-generated method stubreturn mBinder;}@Overridepublic void onCreate() {// TODO Auto-generated method stubsuper.onCreate();Log.i("dazhou", "MainService onCreate");}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {// TODO Auto-generated method stubLog.i("dazhou", "MainService onStartCommand");return super.onStartCommand(intent, flags, startId);}@Overridepublic void onDestroy() {// TODO Auto-generated method stubsuper.onDestroy();}public String getString(){return "dazhou";}public class LocalBinder extends Binder{public MainService getService(){return MainService.this;}}}

二，若Service在进程之间被bind（可以理解为多APP之间）

可以使用Messenger类来实现，方法步骤：首先在Service中构造一个Handler类，用于处理客户端发来的各种消息；其次，在Service中以刚才创建的Handler类的对象为参数创建一个Messenger对象；最后，在Service的onBind方法中返回Messenger.getBinder()。与此同时，也可以在调用Service的Activity中创建Messenger，并将该Messeneger通过Message的replyTo域传给Service，这样就可在Service中向Activity返回消息。这是Google推荐的最简便的IPC方法，因为Messenger将所有的请求放入一堆队列，并使用单线程处理，这么以来开发者就不用考虑自己所实现Service的线程安全问题。实例关键代码如下：

Activity端代码：

public class MainActivity extends ActionBarActivity implements OnClickListener{private Button btn_bind_in_diff_service;private ServiceConnection remoteConn = new ServiceConnection() {@Overridepublic void onServiceDisconnected(ComponentName name) {// TODO Auto-generated method stub}@Overridepublic void onServiceConnected(ComponentName name, IBinder service) {// TODO Auto-generated method stubMessenger messenger = new Messenger(service);Message msg = Message.obtain(null, 1, 0, 0);msg.replyTo = mMessenger;try {messenger.send(msg);} catch (RemoteException e) {// TODO Auto-generated catch blocke.printStackTrace();}}};public class IncomingHandler extends Handler{@Overridepublic void handleMessage(Message msg) {// TODO Auto-generated method stubsuper.handleMessage(msg);int what = msg.what;switch (what) {case 2:Log.v("dazhou", "service return value to activity");break;default:break;}}}private Messenger mMessenger = new Messenger(new IncomingHandler());@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);btn_bind_in_diff_service = (Button)findViewById(R.id.btn_bind_service_in_diff_app);btn_bind_in_diff_service.setOnClickListener(this);}@Overridepublic void onClick(View v) {// TODO Auto-generated method stubint id = v.getId();Intent intent;switch (id) {case R.id.btn_bind_service_in_diff_app:Log.i("dazhou", "bind service in diff app");intent = new Intent();intent.setAction("your action");//startService(intent);bindService(intent, remoteConn, Context.BIND_AUTO_CREATE);break;default:break;}}}

Service端代码：

public class RemoteService extends Service {public Messenger mMessenger = new Messenger(new IncomingHandler()); @Overridepublic IBinder onBind(Intent intent) {// TODO Auto-generated method stubLog.i("dazhou", "remote service onBind");return mMessenger.getBinder();}@Overridepublic void onCreate() {// TODO Auto-generated method stubLog.i("dazhou", "remote service onCreate");super.onCreate();}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {// TODO Auto-generated method stubLog.i("dazhou", "remote service onStartCommand");return super.onStartCommand(intent, flags, startId);}public class IncomingHandler extends Handler{@Overridepublic void handleMessage(Message msg) {// TODO Auto-generated method stubsuper.handleMessage(msg);switch (msg.what) {case 1:Log.i("dazhou", "Remote service incominghandler handlemessage:"+msg.what);Messenger activityMessenger = msg.replyTo;if(activityMessenger!=null){try {Log.v("dazhou", "remote service has receive the activityMessenger:"+activityMessenger.hashCode());activityMessenger.send(Message.obtain(null, 2, 0, 0));} catch (RemoteException e) {// TODO Auto-generated catch blocke.printStackTrace();}}break;default:break;}}}}