AIDL总结

监听服务端死亡

注意 onServiceDisconnected 只有在死亡意外死亡后才会回调，unbindService 不会回调

   mServiceConn = new ServiceConnection() {
      
            @Override
            public void onServiceConnected(ComponentName name, final IBinder service) {
      
                Log.d(TAG, "onServiceConnected");
                try {
      
		    // 设置服务死亡代理，服务死亡后可自动绑定服务
                    service.linkToDeath(new IBinder.DeathRecipient() {
      
                        @Override
                        public void binderDied() {
      
                            Log.d(TAG, "binderDied");
                            service.unlinkToDeath(this, 0);
                            bindService();
                        }
                    }, 0);
                } catch (RemoteException e) {
      
                    e.printStackTrace();
                }
            }

            @Override
            public void onServiceDisconnected(ComponentName name) {
      
                Log.d(TAG, "onServiceDisconnected");
                playerService = null;
            }
        }

监听客户端死亡

private RemoteCallbackList<IMetadataUpdateCallback> callbacks = new RemoteCallbackList<IMetadataUpdateCallback>() {
      
            @Override
            public void onCallbackDied(IMetadataUpdateCallback callback) {
      
                super.onCallbackDied(callback);
                Log.d(TAG, "onCallbackDied:" + callback);
            }
        };

服务端收到的对象并不相同，BinderProxy是相同的

每个进程对应着一个VM，对象无法在进程间传递，binder机制数据传递是通过序列化进行的，

// 客户端
2022-07-16 15:38:39.900 9756-9756/com.example.aidl D/MainActivity: registerMetadataUpdateCallback: [email protected] asBinder:[email protected]
// 服务端
2022-07-16 15:38:39.900 9789-9808/? D/PlayerService: registerMetadataUpdateCallback:[email protected] asBinder: [email protected]
2022-07-16 15:39:00.620 9789-9808/com.example.aidl:Remote D/PlayerService: unregisterMetadataUpdateCallback:[email protected] asBinder: [email protected]

RemoteCallbackList作用​

1.以IBinder-Callback的键值对形式，存储Callback，

2.添加死亡代理监听，自动清除Callback

3.将map中value复制到数据中，来保证多线程安全

4.源码mCallbacks用来存储Callback，mActiveBroadcast在调用时保存mCallbacks.values，来保证多线程安全

ArrayMap < IBinder, Callback > mCallbacks = new ArrayMap < IBinder, Callback > ();
private Object[] mActiveBroadcast;
public int beginBroadcast() {
      
    synchronized(mCallbacks) {
      
        if(mBroadcastCount > 0) {
      
            throw new IllegalStateException("beginBroadcast() called while already in a broadcast");
        }
        final int N = mBroadcastCount = mCallbacks.size();
        if(N <= 0) {
      
            return 0;
        }
        Object[] active = mActiveBroadcast;
        if(active == null || active.length < N) {
      
            mActiveBroadcast = active = new Object[N];
        }
        for(int i = 0; i < N; i++) {
      
            active[i] = mCallbacks.valueAt(i);
        }
        return N;
    }
}
public E getBroadcastItem(int index) {
      
    return((Callback) mActiveBroadcast[index]).mCallback;
}
public void finishBroadcast() {
      
    synchronized(mCallbacks) {
      
        if(mBroadcastCount < 0) {
      
            throw new IllegalStateException("finishBroadcast() called outside of a broadcast");
        }
        Object[] active = mActiveBroadcast;
        if(active != null) {
      
            final int N = mBroadcastCount;
            for(int i = 0; i < N; i++) {
      
                active[i] = null;
            }
        }
        mBroadcastCount = -1;
    }
}

权限校验

可以在Service中onBind方法返回Binder对象时进行校验或者在自定义Binder类中onTransact进行校验

 <permission android:name="com.example.aidl.BookService" android:protectionLevel="signature" />

<uses-permission android:name="com.example.aidl.BookService" />

@Override
public IBinder onBind(Intent intent) {
      
    Log.d(TAG, "onBind");
    if(checkCallingOrSelfPermission(PERMISSION) == PackageManager.PERMISSION_DENIED) {
      
        Log.d(TAG, "Bind PlayerService need permission example.permission.TEST_AIDL, are you have?");
        return null;
    }
    return mBinder;
}

数据流向

• in

  基本数据类型只能为in，可以不用加

  oneway 只能是in

• out

• inout

https://www.jianshu.com/p/31898ea2dfa3

oneway

• binder默认是同步调用的，会挂起客户端直至完成，oneawy是异步调用

• oneway 修饰的方法返回值只能是void