Android中使用Messenger進行兩個進程之間的數據交換，也就是IPC

不一樣App（進程）之間的數據交換，使用帶到的核心技術是Messenger

技術概述

Messenger的核心也就是Message和Handler，一樣是Service提供方法，供其餘地方進行調用

1. Service代碼示例

public class MyService extends Service {
	class ServiceHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case 1:
                    Log.i("MyService", "msg.what is 1");
                    break;
                default:
                    super.handleMessage(msg);
            }
            super.handleMessage(msg);
        }
    }

	final Messenger messenger = new Messenger(new ServiceHandler());

	@Override
    public IBinder onBind(Intent intent) {
        Log.i("MyService", "service is binded");
        return messenger.getBinder();
    }
}

2. 因爲須要別的App來調用，因此這個Service在AndroidManifest須要進行一些屬性的設置，具體以下

<service
            android:name=".MyService"
            android:enabled="true"
            android:exported="true" >
            <intent-filter>
                <action android:name="com.serviceHandler" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </service>

3. Activity代碼示例

public class MainActivity extends Activity {
	@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
	}
	Messenger messenger = null;
    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
            messenger = new Messenger(iBinder);
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {
           messenger = null;
        }
    };

    @Override
    protected void onStart() {
        super.onStart();
        Log.i("MyActivity", "activity start bind service");
        Intent it = new Intent();
		// 這個設置的是Service所在的AndroidManifest裏面設置的action屬性
        it.setAction("com.serviceHandler");
		// 這個是Service的包名
        it.setPackage("com.test");
        bindService(it, serviceConnection, Context.BIND_AUTO_CREATE);
    }

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

	// 執行這個方法，會在logcat看到 'msg.what is 1' 的消息輸出，這樣就能夠經過Message來進行數據交互了
    public void testBindService(View v){
        Message msg = Message.obtain();
        msg.what = 1;
        try {
            messenger.send(msg);
        }catch (Exception e) {
            Log.e("MyActivity", utils.getExceptionMsg(e));
        }
    }
}