Android在framework中新增AIDL接口_android framework 添加aidl

1、背景

项目中遇到一个需求，要对Mdmservice进行管控。简化下来大概就是需要监听一个系统属性值，当这个属性值变为false的时候，禁止调用扬声器、听筒。跟踪代码发现这个需求里面的场景，只需要处理MediaRecorder就能达到目标。
2、实现

根据需求，调用扬声器、听筒之前读取一下系统属性值判断一下即可，有个场景是正在调用扬声器、听筒的过程中属性值发生变化，着重要处理的就是这个场景。
2.1 定义AIDL接口

接口名称定为INotifyPolicyChange.aidl，直接给出代码：

/*
* server use this interface of client
*/
interface INotifyPolicyChange {
    void notifyPolicyChange();
}

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2.2 在IMdmService.aidl中定义注册、去注册接口

interface IMdmService {
      //Interactive interface
      void registerCallBack(IBinder token, INotifyPolicyChange callback);
      void unregisterCallBack(INotifyPolicyChange callback);
……
}
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2.3 在MdmService中实现注册、去注册

给出代码片段：

private RemoteCallbackList<INotifyPolicyChange> mCallBacks = new RemoteCallbackList<>();

final class ClientDeathCallback implements DeathRecipient {
            public final IBinder mToken;
            public final INotifyPolicyChange mCallback;
            public ClientDeathCallback(IBinder token, INotifyPolicyChange mCallback) {
                this.mToken = token;
                this.mCallback = mCallback;
            }

            @Override
            public void binderDied() {
                Log.d(TAG,"client died! mToken=" + mToken + ";callback=" + mCallback);
                try {
                    unregisterCallBack(mCallback);
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        }

        public void registerCallBack(IBinder token, INotifyPolicyChange callback) throws RemoteException {
            ClientDeathCallback clientDeathCallback = new ClientDeathCallback(token, callback);
            //register callback
            mCallBacks.register(callback);
            //register recipient
            token.linkToDeath(clientDeathCallback, 0);
        }

        public void unregisterCallBack(INotifyPolicyChange callback) throws RemoteException {
            mCallBacks.unregister(callback);
        }

        /**
        * notify client that policy change
        */

        private void notifyChange() {
            final int len = mCallBacks.beginBroadcast();
            for(int i = 0; i < len; i++) {
                try {
                    mCallBacks.getBroadcastItem(i).notifyPolicyChange();
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
            mCallBacks.finishBroadcast();
        }

public boolean setMicrophonePolicy(int policy) throws RemoteException {
            if(isActive) {
                boolean success = MdmDevicePolicyManager.getInstance(mContext)
                        .getPeripheralPolicy().setMicrophonePolicy(policy);
                //notify client policy changed
                if(success) {
                    notifyChange();
                }
                return success;
            }
            return false;
        }
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2.4 在MediaRecorder中实现业务逻辑

给出代码片段：

private IBinder mBinder;
private IMdmService mMdmService;
public MediaRecorder() {
//get mdmservice mBinder and register a callback
        mBinder = ServiceManager.getService("mdm3");
        mMdmService = mBinder == null ? null : IMdmService.Stub.asInterface(mBinder);
        if(mMdmService != null) {
            try {
                mMdmService.registerCallBack(new Binder(), mNotifyCallBack);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        } else {
            Log.e(TAG, "MediaRecorder cannot get mdmservice mBinder!");
        }
}

private INotifyPolicyChange mNotifyCallBack = new INotifyPolicyChange.Stub() {
        @Override
        public void notifyPolicyChange() throws RemoteException {
            //add logic here
        }
    };

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mBinder = ServiceManager.getService("mdm3");这句代码能获取到MdmService实例是因为在SystemService已经以“mdm3”对MdmService注册过了。
2.5 在mk及其他文件里注册新增AIDL文件

新增了AIDL之后，需手动注册，否则编译时找不到相应文件。

core/java/android/service/mdm3/INotifyPolicyChange.aidl
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编译过后，“api/current.txt”、“api/system-current.txt”、“api/test-current”也新增了相应接口。
这样，就完成了在framework中新增一个AIDL接口。