android Binder 实现异步回调

场景描述

此时有A、B两个进程，期望A与B实现进程间通信，并且在逻辑执行完毕后再A进程触发回调。期望过程如下：

1. A进程 调用function()
2. B进程 触发function()
3. B进程 调用callback()
4. A进程 触发callback()

执行效果

笔者demo中通过打log来记录方法的执行。
执行过程大致如下：

1. 主进程 bindService
2. remote进程 执行function()，在function中调用callback()。
3. 主进程 执行callback()
   
   

代码

主要内容如下：

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private IServer iServer;
    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            iServer = IServer.Stub.asInterface(service);
            System.out.println("onServiceConnected");
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            System.out.println("onServiceDisconnected");
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        Button btnBind = findViewById(R.id.btn_bind);
        btnBind.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //绑定service
                Intent intent = new Intent(MainActivity.this, RemoteTestService.class);
                bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);
            }
        });

        Button btnTest = findViewById(R.id.btn_test);
        btnTest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    //注册回调方法
                    iServer.setCallBack(new ICallBack.Stub() {
                        @Override
                        public void callback() throws RemoteException {
                            System.out.println("ICallBack callback()");
                        }
                    });
                    //触发远程调用
                    iServer.testFunction();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

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

RemoteTestService.java

/**
 * 进程间通信的service
 */
public class RemoteTestService extends Service {

    private final ServerBinder serverBinder = new ServerBinder();

    @Override
    public IBinder onBind(Intent intent) {
        return serverBinder;
    }

}

ServerBinder.java

/**
 * IServer.aidl的实现
 */
public class ServerBinder extends IServer.Stub {

    @Override
    public void testFunction() throws RemoteException {
        System.out.println("IServer testFunction()");

        //调用callback
        int i = RemoteCallbackManager.getInstance().callbackList.beginBroadcast();
        while (i > 0) {
            i--;
            try {
                RemoteCallbackManager.getInstance().callbackList.getBroadcastItem(i).callback();
                RemoteCallbackManager.getInstance().callbackList.unregister(RemoteCallbackManager.getInstance().callbackList.getBroadcastItem(i));
            } catch (RemoteException e) {
                // The RemoteCallbackList will take care of removing
                // the dead object for us.
            }
        }
        RemoteCallbackManager.getInstance().callbackList.finishBroadcast();
    }

    @Override
    public void setCallBack(ICallBack callBack) throws RemoteException {
        //绑定callback
        RemoteCallbackManager.getInstance().callbackList.register(callBack);
    }
}

RemoteCallbackManager.java

/**
 * 用于存储RemoteCallbackList的单例
 */
public class RemoteCallbackManager {

    public RemoteCallbackList<ICallBack> callbackList;

    private RemoteCallbackManager() {
        callbackList = new RemoteCallbackList<>();
    }

    private static class Host {
        private static RemoteCallbackManager instance = new RemoteCallbackManager();
    }

    public static RemoteCallbackManager getInstance() {
        return Host.instance;
    }
}

IServer.aidl

interface IServer {
   void testFunction();
   void setCallBack(com.example.bindercallbacktest.ICallBack callback);
}

ICallBack.aidl

interface ICallBack {
    void callback();
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.bindercallbacktest">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service
            android:name=".RemoteTestService"
            android:process=":remote" />

    </application>

</manifest>