Android学习笔记-service进程间通信（二）

有时候service和activity之间需要比较复杂的交互，需要双向通信，这时候就可以使用messenger了

1. 在service中定义handler类处理message
2. 使用自定义的handler实例化messenger
3. 在onbinder中返回messenger的binder引用
4. 在activity中得到service的messenger引用
5. 如果需要service向activity发送消息，在activity获得service的messenger后向service发送reply中有activity的messenger引用的message

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service中主要代码

 private final Messenger mMessenger = new Messenger(new IncomingHandler());

    /**
     * Handler of incoming messages from clients.
     */
    class IncomingHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_SEND_NOTIFICATION:
                    int howManyConversations = msg.arg1 <= 0 ? 1 : msg.arg1;
                    int messagesPerConv = msg.arg2 <= 0 ? 1 : msg.arg2;
                    sendNotification(howManyConversations, messagesPerConv);
                    break;
                default:
                    super.handleMessage(msg);
            }
        }
    }

activity中

private ServiceConnection mConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder service) {
            mService = new Messenger(service);
            mBound = true;
            setButtonsState(true);
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {
            mService = null;
            mBound = false;
            setButtonsState(false);
        }
    };