Android 多进程开发 - 服务端死亡回调、服务端与客户端的线程环境、oneway 关键字

一、服务端死亡回调

• 在绑定服务端时，可以获取服务端时的 Binder 对象，调用 Binder 对象的 linkToDeath 方法，注册死亡回调，监听服务端时是否挂了

privateIMyAidlInterfacemyAidlInterface;privatebooleanisBound=false;privatefinalIBinder.DeathRecipientdeathRecipient=newIBinder.DeathRecipient(){@OverridepublicvoidbinderDied(){Log.i(TAG,"检测到服务端进程死亡");}};privateServiceConnectionconnection=newServiceConnection(){@OverridepublicvoidonServiceConnected(ComponentNamename,IBinderservice){Log.i(TAG,"服务连接成功");myAidlInterface=IMyAidlInterface.Stub.asInterface(service);try{service.linkToDeath(deathRecipient,0);}catch(RemoteExceptione){e.printStackTrace();}isBound=true;}@OverridepublicvoidonServiceDisconnected(ComponentNamename){Log.i(TAG,"服务连接断开");myAidlInterface=null;isBound=false;// 系统会处理 unlinkToDeath、unbindService}};

• 触发 onServiceDisconnected 回调，系统会处理 unlinkToDeath、unbindService，不需要手动调用，详见源码

// 1. doDeath 方法源码publicvoiddoDeath(ComponentNamename,IBinderservice){synchronized(this){ConnectionInfoold=mActiveConnections.get(name);if(old==null||old.binder!=service){// Death for someone different than who we last// reported... just ignore it.return;}mActiveConnections.remove(name);old.binder.unlinkToDeath(old.deathMonitor,0);}mConnection.onServiceDisconnected(name);}

// doDeath 方法中的清理逻辑mActiveConnections.remove(name);old.binder.unlinkToDeath(old.deathMonitor,0);

// 2. doConnected 方法publicvoiddoConnected(ComponentNamename,IBinderservice,booleandead){ServiceDispatcher.ConnectionInfoold;ServiceDispatcher.ConnectionInfoinfo;synchronized(this){if(mForgotten){// We unbound before receiving the connection; ignore// any connection received.return;}old=mActiveConnections.get(name);if(old!=null&&old.binder==service){// Huh, already have this one. Oh well!return;}if(service!=null){// A new service is being connected... set it all up.info=newConnectionInfo();info.binder=service;info.deathMonitor=newDeathMonitor(name,service);try{service.linkToDeath(info.deathMonitor,0);mActiveConnections.put(name,info);}catch(RemoteExceptione){// This service was dead before we got it... just// don't do anything with it.mActiveConnections.remove(name);return;}}else{// The named service is being disconnected... clean up.mActiveConnections.remove(name);}if(old!=null){old.binder.unlinkToDeath(old.deathMonitor,0);}}// If there was an old service, it is now disconnected.if(old!=null){mConnection.onServiceDisconnected(name);}if(dead){mConnection.onBindingDied(name);}else{// If there is a new viable service, it is now connected.if(service!=null){mConnection.onServiceConnected(name,service);}else{// The binding machinery worked, but the remote returned null from onBind().mConnection.onNullBinding(name);}}}

// doConnected 方法中的清理逻辑if(old!=null){old.binder.unlinkToDeath(old.deathMonitor,0);}

二、服务端与客户端的线程环境

1、服务端

1. AIDL 接口，在主线程执行（无论客户端是在主线程调用，还是在子线程调用）

privatefinalIMyAidlInterface.Stubbinder=newIMyAidlInterface.Stub(){@Overridepublicintadd(inta,intb)throwsRemoteException{// Binder 线程returna+b;}}

2. DeathRecipient 回调，在 Binder 线程执行

IBinder.DeathRecipientdr=newDeathRecipient(){@OverridepublicvoidbinderDied(){// Binder 线程}};

2、客户端

1. ServiceConnection 回调，在主线程执行

privateServiceConnectionconnection=newServiceConnection(){@OverridepublicvoidonServiceConnected(ComponentNamename,IBinderservice){// 主线程}@OverridepublicvoidonServiceDisconnected(ComponentNamename){// 主线程}};

2. DeathRecipient 回调，在 Binder 线程执行

privatefinalIBinder.DeathRecipientdeathRecipient=newIBinder.DeathRecipient(){@OverridepublicvoidbinderDied(){// 主线程}};

3. AIDL 接口调用，调用前后都是在调用者线程执行

try{// 主线程intresult=myAidlInterface.add(5,3);Log.i(TAG,"add result: "+result);// 主线程}catch(RemoteExceptione){e.printStackTrace();Log.e(TAG,"add method error: "+e.getMessage());}

newThread(()->{try{// 子线程intresult=myAidlInterface.add(5,3);Log.i(TAG,"add result: "+result);// 子线程}catch(RemoteExceptione){e.printStackTrace();Log.e(TAG,"add method error: "+e.getMessage());}}).start();

4. AIDL 接口回调，在主线程执行（无论客户端是在主线程注册，还是在子线程注册）

callback=newIPlayerCallback.Stub(){@OverridepublicvoidonSongChanged(StringsongName)throwsRemoteException{// 主线程Log.i(TAG,"onSongChanged: "+songName);}@OverridepublicvoidonPlayStateChanged(booleanisPlaying)throwsRemoteException{// 主线程Log.i(TAG,"onPlayStateChanged: "+isPlaying);}};try{myAidlInterface.registerCallback(callback);Log.i(TAG,"registerCallback method success");}catch(RemoteExceptione){e.printStackTrace();Log.e(TAG,"registerCallback method error: "+e.getMessage());}

newThread(()->{callback=newIPlayerCallback.Stub(){@OverridepublicvoidonSongChanged(StringsongName)throwsRemoteException{// 主线程Log.i(TAG,"onSongChanged: "+songName);}@OverridepublicvoidonPlayStateChanged(booleanisPlaying)throwsRemoteException{// 主线程Log.i(TAG,"onPlayStateChanged: "+isPlaying);}};try{myAidlInterface.registerCallback(callback);Log.i(TAG,"registerCallback method success");}catch(RemoteExceptione){e.printStackTrace();Log.e(TAG,"registerCallback method error: "+e.getMessage());}}).start();

三、oneway 关键字

1、基本介绍

• oneway 关键字修饰的方法，客户端调用后立即返回，不等待服务端执行完成

onewayvoiddoSomething();

2、注意事项

1. oneway 方法不能有返回值，否则编译报错

onewayStringdoSomething();

# 输出结果 oneway method 'doSomething' cannot return a value

2. oneway 方法的参数可以用 in 修饰

onewayvoiddoSomething(inbyte[]data);

3. oneway 方法的参数不能用 out 或 inout 修饰，否则编译报错

onewayvoiddoSomething(outbyte[]data);

# 输出结果 oneway method 'doSomething' cannot have out parameters

onewayvoiddoSomething(inoutbyte[]data);

# 输出结果 oneway method 'doSomething' cannot have out parameters