Android IPC机制Messenger实例详解

public final class Messenger implements Parcelable {
  private final IMessenger mTarget;

  public Messenger(Handler target) {
    mTarget = target.getIMessenger();
  }

  public void send(Message message) throws RemoteException {
    mTarget.send(message);
  }

  public IBinder getBinder() {
    return mTarget.asBinder();
  }

  public boolean equals(Object otherObj) {
    if (otherObj == null) {
      return false;
    }
    try {
      return mTarget.asBinder().equals(((Messenger)otherObj)
          .mTarget.asBinder());
    } catch (ClassCastException e) {
    }
    return false;
  }

  public int hashCode() {
    return mTarget.asBinder().hashCode();
  }

  public int describeContents() {
    return 0;
  }

  public void writeToParcel(Parcel out, int flags) {
    out.writeStrongBinder(mTarget.asBinder());
  }

  public static final Parcelable.Creator<Messenger> CREATOR
      = new Parcelable.Creator<Messenger>() {
    public Messenger createFromParcel(Parcel in) {
      IBinder target = in.readStrongBinder();
      return target != null ? new Messenger(target) : null;
    }

    public Messenger[] newArray(int size) {
      return new Messenger[size];
    }
  };

  public static void writeMessengerOrNullToParcel(Messenger messenger,
      Parcel out) {
    out.writeStrongBinder(messenger != null ? messenger.mTarget.asBinder()
        : null);
  }

  public static Messenger readMessengerOrNullFromParcel(Parcel in) {
    IBinder b = in.readStrongBinder();
    return b != null ? new Messenger(b) : null;
  }

  public Messenger(IBinder target) {
    mTarget = IMessenger.Stub.asInterface(target);
  }
}

public class MessageService extends Service {

  private Messenger mMessenger = new Messenger(new Handler() {
    @Override
    public void handleMessage(Message msgFromClient) {
      super.handleMessage(msgFromClient);
      Message msgToTarget = Message.obtain(msgFromClient);
      msgToTarget.what = 0;
      try {
        Thread.sleep(2000);
        msgToTarget.arg1 = msgFromClient.arg1 + msgFromClient.arg2;
        msgFromClient.replyTo.send(msgToTarget);
      } catch (InterruptedException e) {
        e.printStackTrace();
      } catch (RemoteException e) {
        e.printStackTrace();
      }
    }
  });

  @Nullable
  @Override
  public IBinder onBind(Intent intent) {
    return mMessenger.getBinder();
  }
}

 Messenger mMessenger = new Messenger(new Handler() {
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      Log.w("Jayuchou", "--- 从异步线程中读取到数据 --- " + msg.arg1);
    }
  });

  Messenger mService;

  ServiceConnection connection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
      mService = new Messenger(service);
      Log.w("Jayuchou", "-- Connected success --");
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
      Log.w("Jayuchou", "-- Connected dismiss --");
      mService = null;
    }
  };

     Message msgFromClient = Message.obtain(null, 0, 1, 2);
        msgFromClient.replyTo = mMessenger;
        try {
          mService.send(msgFromClient);
        } catch (RemoteException e) {
          e.printStackTrace();
        }

msgFromClient.replyTo.send(msgToTarget);