Android 多程序之Messenger的使用
阿新 • • 發佈:2018-12-14
Android多程序系列
Messenger也可以作為Android多程序的一種通訊方式,通過構建Message來在客戶端和服務端之間傳遞資料
簡單使用Messenger
客戶端通過Messenger向服務端程序傳送訊息
- 構建一個執行在獨立程序中的服務端Service:
public class MessengerService extends Service { private static final String TAG = "MessagerService"; /** * 處理來自客戶端的訊息,並用於構建Messenger */ private static class MessengerHandler extends Handler { @Override public void handleMessage(Message message) { switch (message.what) { case MESSAGE_FROM_CLIENT: Log.e(TAG, "receive message from client:" + message.getData().getString("msg")); break; default: super.handleMessage(message); break; } } } /** * 構建Messenger物件 */ private final Messenger mMessenger = new Messenger(new MessengerHandler()); @Nullable @Override public IBinder onBind(Intent intent) { //將Messenger物件的Binder返回給客戶端 return mMessenger.getBinder(); } }
- 註冊service,當然要設定在不同的程序
<service
android:name="com.xxq2dream.service.MessengerService"
android:process=":remote" />
- 然後客戶端是通過繫結服務端返回的binder來建立Messenger物件,並通過這個Messenger物件來向服務端傳送訊息
public class MessengerActivity extends AppCompatActivity { private static final String TAG = "MessengerActivity"; private Messenger mService; private ServiceConnection mConnection = new ServiceConnection() { @Override public void onServiceConnected(ComponentName componentName, IBinder iBinder) { Log.e(TAG, "ServiceConnection-->" + System.currentTimeMillis()); //通過服務端返回的Binder建立Messenger mService = new Messenger(iBinder); //建立訊息,通過Bundle傳遞資料 Message message = Message.obtain(null, MESSAGE_FROM_CLIENT); Bundle bundle = new Bundle(); bundle.putString("msg", "hello service,this is client"); message.setData(bundle); try { //向服務端傳送訊息 mService.send(message); } catch (RemoteException e) { e.printStackTrace(); } } @Override public void onServiceDisconnected(ComponentName componentName) { Log.e(TAG, "onServiceDisconnected-->binder died"); } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_messenger); //繫結服務 Intent intent = new Intent(this, MessengerService.class); bindService(intent, mConnection, Context.BIND_AUTO_CREATE); } @Override protected void onDestroy() { //解綁服務 unbindService(mConnection); super.onDestroy(); } }
服務端接收到客戶端的訊息
通過上面的額實踐,我們可以看出利用Messenger進行跨程序通訊,需要通過Message來傳遞訊息,而Message可以通過setData方法利用Bundle來傳遞複雜的資料。
服務端如果要回復訊息給客戶端,那就要用到Message的replyTo引數了
- 服務端改造
private static class MessengerHandler extends Handler { @Override public void handleMessage(Message message) { switch (message.what) { case Constant.MESSAGE_FROM_CLIENT: Log.e(TAG, "receive message from client:" + message.getData().getString("msg")); //獲取客戶端傳遞過來的Messenger,通過這個Messenger回傳訊息給客戶端 Messenger client = message.replyTo; //當然,回傳訊息還是要通過message Message msg = Message.obtain(null, Constant.MESSAGE_FROM_SERVICE); Bundle bundle = new Bundle(); bundle.putString("msg", "hello client, I have received your message!"); msg.setData(bundle); try { client.send(msg); } catch (RemoteException e) { e.printStackTrace(); } break; default: super.handleMessage(message); break; } } }
- 客戶端改造,主要是通過Handle構建一個Messenger物件,並在向服務端傳送訊息的時候,通過Message的replyTo引數將Messenger物件傳遞給服務端
/**
* 用於構建客戶端的Messenger物件,並處理服務端的訊息
*/
private static class MessengerHandler extends Handler {
@Override
public void handleMessage(Message message) {
switch (message.what) {
case Constant.MESSAGE_FROM_SERVICE:
Log.e(TAG, "receive message from service:" + message.getData().getString("msg"));
break;
default:
super.handleMessage(message);
break;
}
}
}
/**
* 客戶端Messenger物件
*/
private Messenger mClientMessenger = new Messenger(new MessengerHandler());
private ServiceConnection mConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
Log.e(TAG, "ServiceConnection-->" + System.currentTimeMillis());
mService = new Messenger(iBinder);
Message message = Message.obtain(null, MESSAGE_FROM_CLIENT);
Bundle bundle = new Bundle();
bundle.putString("msg", "hello service,this is client");
message.setData(bundle);
//將客戶端的Messenger物件傳遞給服務端
message.replyTo = mClientMessenger;
try {
mService.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
Log.e(TAG, "onServiceDisconnected-->binder died");
}
};
客戶端收到服務端的訊息回覆
總結
- 使用Messager來傳遞Message,Message中能使用的欄位只有what、arg1、arg2、Bundle和replyTo,自定義的Parcelable物件無法通過object欄位來傳輸
- Message中的Bundle支援多種資料型別,replyTo欄位用於傳輸Messager物件,以便程序間相互通訊
- Messager以序列的方式處理客戶端發來的訊息,不適合有大量併發的請求
- Messager方法只能傳遞訊息,不能跨程序呼叫方法
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