java - 通过绑定(bind)服务从服务到 Activity 进行通信

Question

我已经按照本教程将 Activity 绑定(bind)到我的服务。 http://developer.android.com/guide/components/bound-services.html

我可以调用服务函数，但是如果我想更改我的一些 TextView 或禁用一些切换按钮，因为在服务上(以及从服务上)完成了工作，该怎么办。有没有一种简单的方法可以做到这一点？

Answer 1

您可以使用消息在 Activity 和服务之间发送信息。这是发送简单数据的简便方法，但如果您需要非常频繁地发送数据或发送复杂数据，则可能不是最佳选择。这是我的一个应用程序中的一些代码示例，其中包含一项服务和一项通信 Activity :

Activity 中的代码:

//this is where you set what you want to happen
class IncomingHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            //this switch reads the information in the message (usually just 
            //an integer) and will do something depending on which integer is sent
            case 1: do_something();
            case 2: do_something_2(); //etc.
            default:
                super.handleMessage(msg);
        }
    }
}

final Messenger myMessenger = new Messenger(new IncomingHandler());

private ServiceConnection mConnection = new ServiceConnection() {
    public void onServiceConnected(ComponentName className,
            IBinder service) {
        myService = new Messenger(service);
        myCallbackText = (TextView)findViewById(R.id.tv01); //This is a text view which will display status information as needed
        myCallbackText.setText("Attached.");

        try {
            Message msg = Message.obtain(null,
                    1);
            msg.replyTo = mMessenger; //here we send an instance of our messenger implementation as the replyTo address
            mService.send(msg);

            msg = Message.obtain(null,
                    3, this.hashCode(), 0);
            mService.send(msg); //send a message with the value "3"
        } catch (RemoteException e) {
          //nothing you can do if the server isn't active
        }

        Toast.makeText(Service_testActivity.this, R.string.remote_service_connected,
                Toast.LENGTH_SHORT).show();//confirmation that the connection happened successfully
    }

    public void onServiceDisconnected(ComponentName className) {
        // This is called when the connection with the service has been
        // unexpectedly disconnected -- that is, its process crashed.
        mService = null;
        mCallbackText = (TextView)findViewById(R.id.tv01);//same textview as before
        mCallbackText.setText("Disconnected.");

        Toast.makeText(Service_testActivity.this, R.string.remote_service_disconnected,
                Toast.LENGTH_SHORT).show();
    }
};

服务中的代码: 在该服务中，您将希望有代码(与 Activity 中的代码非常相似)来接收消息并将 msg.replyTo 字段保存为 Messenger 对象。某处有一个示例，您可以创建一个对象，然后像这样使用 IncomingHandler:

ArrayList<Messenger> mClients = new ArrayList<Messenger>();
class IncomingHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MSG_REGISTER_CLIENT:
                mClients.add(msg.replyTo);
                break;
            case MSG_UNREGISTER_CLIENT:
                mClients.remove(msg.replyTo);
                break;
            default:
                super.handleMessage(msg);
        }
    }
}

这可以让您的服务同时跟踪多个客户端并向指定的客户端发送消息。要发送消息，只需使用如下内容:

mClients.get(1).send(Message.obtain(null, 3, new Random().nextInt(), 0));
//sends a message to the first client saved in the list