Android如何实现跨进程接口回掉

时间 2019-12-12

原文原文链接

同一个进程内实现接口回掉很简单，这里不作叙述，本文主要讲的是跨进程的接口回掉实现方式。有一种跨进程通讯的方式就是使用AIDL，可是单纯的AIDL通讯只能够实现客户端访问服务端主动获取Binder对象，若是服务端有变化没法及时通知客户端。如今能够经过AIDL跨进程接口回掉来解决服务端发生变化通知客户端的问题。java

谷歌提供了RemoteCallbackList来实现对IInterface的管理。public class RemoteCallbackList<E extends IInterface>bash

首先定义两个AIDL文件：

ITestCallBack.aidl

interface ITestCallBack {
    /**
     * Demonstrates some basic types that you can use as parameters
     * and return values in AIDL.
     */
    void onTagValid(in String tag);

}
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ITestInterface.aidl 在注册和反祖册方法中，须要传入ITestCallBack的对象

interface ITestInterface {
    /**
     * Demonstrates some basic types that you can use as parameters
     * and return values in AIDL.
     */
     boolean isTagValid(in String tag);

     void registerCallback(in String tag, in ITestCallBack callback);

     void unRegisterCallback(in String tag, in ITestCallBack callback);
}复制代码

服务端：

建立Service，而且在service中定义RemoteCallbackList集合，实现ITestInterface.Stub，在registerCallback,和unRegisterCallback中，分别将ITestCallBack对象注册和反注册进RemoteCallbackList中。RemoteCallbackList提供了获取注册进去的IInterface对象方法。app

//其实RemoteCallbackList相似于java中{@link java.util.Observable}，用来批量处理接口回调对象，
//其实若是确保只有一个客户端会bind到这个服务，只须要保存一个IMyAidlInterfaceCallback便可。
//可是若是有多个，强烈推荐使用其实RemoteCallbackList

public void callBack() {
    if (mCallBacks == null) {
        return;
    }
    int num = mCallBacks.beginBroadcast();
    for (int i = 0; i < num; i++) {
        try {
            mCallBacks.getBroadcastItem(i).onTagValid("congratulation callback success " + tag);
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }
    //结束后必定要使用finsh，不然下次执行beginBroadcast会抛出IllegalStateException异常
    mCallBacks.finishBroadcast();
}复制代码

在isTagValid中能够调用callBack方法去遍历注册的接口对象，也能够当服务端有变化时主动调用callBack方法去通知客户端，这样就实现了服务端变化主动通知客户端。可根据实际方法修改。ide

在service的onBind方法中，返回ITestInterface.Stub的对象便可，等待客户端绑定服务端。ui

下面是服务端Service的代码：this

public class TestService extends Service {

    private RemoteCallbackList<ITestCallBack> mCallBacks = new RemoteCallbackList<>();
    private String tag = "hy";

    public TestService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        return iTestInterface;
    }

    @Override
    public boolean onUnbind(Intent intent) {
        return super.onUnbind(intent);
    }

    ITestInterface.Stub iTestInterface = new ITestInterface.Stub() {
        @Override
        public boolean isTagValid(String tag) throws RemoteException {
            if (tag.equals(TestService.this.tag)) {
                callBack();
                return true;
            }
            return false;
        }

        @Override
        public void registerCallback(String tag, ITestCallBack callback) throws RemoteException {
            if (null != mCallBacks && null != callback) {
                mCallBacks.register(callback);
            }
        }

        @Override
        public void unRegisterCallback(String tag, ITestCallBack callback) throws RemoteException {
            if (null != mCallBacks && null != callback) {
                mCallBacks.unregister(callback);
            }
        }
    };

    public void callBack() {
        if (mCallBacks == null) {
            return;
        }
        int num = mCallBacks.beginBroadcast();
        for (int i = 0; i < num; i++) {
            try {
                mCallBacks.getBroadcastItem(i).onTagValid("congratulation callback success " + tag);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }
        mCallBacks.finishBroadcast();
    }
}复制代码

客户端：

客户端首先要作的是绑定服务端，实现AIDL的通讯，在客户端建立绑定按钮，解绑按钮，和主动获取信息的通讯按钮。在主动获取信息的通讯按钮中实现iTestInterface对象的isTagValid方法能够主动去获取服务端的信息（服务端在isTagValid方法中调用了callBack方法）。spa

客户端代码：code

public class MainActivity extends AppCompatActivity {

    private String tag = "hy";
    private ITestInterface iTestInterface;
    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            iTestInterface = ITestInterface.Stub.asInterface(service);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            iTestInterface = null;
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bindService();
        ((Button) findViewById(R.id.buttonregister)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    iTestInterface.registerCallback(tag, new ITestCallBack.Stub() {
                        @Override
                        public void onTagValid(String tag) throws RemoteException {
                            Log.e("test", "registerCallback: " + tag);
                        }
                    });
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        });

        ((Button) findViewById(R.id.buttonunregister)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    iTestInterface.unRegisterCallback(tag, new ITestCallBack.Stub() {
                        @Override
                        public void onTagValid(String tag) throws RemoteException {

                        }
                    });
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        });

        ((Button) findViewById(R.id.buttonisvalid)).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    iTestInterface.isTagValid(tag);
                } catch (RemoteException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    private void bindService() {
        Intent intent = new Intent();
        intent.setAction("com.example.heyang.myapplication.TestService");
        intent.setPackage("com.example.heyang.myapplication");
        boolean success = bindService(intent, connection, Context.BIND_AUTO_CREATE);
        if (success) {
            Log.e("test ", "bindService OK");
        } else {
            Log.e("test ", "bindService Fail");
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unBindeService();
    }

    private void unBindeService() {
        try {
            unbindService(connection);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
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