android Binder 實現異步回調

場景描述

此時有A、B兩個進程，期望A與B實現進程間通信，並且在邏輯執行完畢後再A進程觸發回調。期望過程如下：

1. A進程 調用function()
2. B進程 觸發function()
3. B進程 調用callback()
4. A進程 觸發callback()

執行效果

筆者demo中通過打log來記錄方法的執行。
執行過程大致如下：

1. 主進程 bindService
2. remote進程 執行function()，在function中調用callback()。
3. 主進程 執行callback()
   
   

代碼

主要內容如下：

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) {
                //綁定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 {
                    //註冊回調方法
                    iServer.setCallBack(new ICallBack.Stub() {
                        @Override
                        public void callback() throws RemoteException {
                            System.out.println("ICallBack callback()");
                        }
                    });
                    //觸發遠程調用
                    iServer.testFunction();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

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

RemoteTestService.java

/**
 * 進程間通信的service
 */
public class RemoteTestService extends Service {

    private final ServerBinder serverBinder = new ServerBinder();

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

}

ServerBinder.java

/**
 * IServer.aidl的實現
 */
public class ServerBinder extends IServer.Stub {

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

        //調用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 {
        //綁定callback
        RemoteCallbackManager.getInstance().callbackList.register(callBack);
    }
}

RemoteCallbackManager.java

/**
 * 用於存儲RemoteCallbackList的單例
 */
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>