Android開發基礎之Worker線程向Main線程發送消息

由於Worker線程不能修改UI，所以當在Worker線程中接收到消息之後，需要通知主線程來更新UI。

下面是一個下例子：

一 布局

    private TextView textView;
    private Button button;
    private NetworkHandler handler_network;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = (TextView)this.findViewById(R.id.textView);

        button = (Button)this.findViewById(R.id.button);
        button.setOnClickListener(new ButtonListener());

        handler_network = new NetworkHandler();
    }

    class ButtonListener implements View.OnClickListener {

        @Override
        public void onClick(View v) {
            NetworkThread thread = new NetworkThread();
            thread.start();
        }
    }

    class NetworkHandler extends Handler{
        public void handleMessage(Message msg){
            String str = (String)msg.obj;
            textView.setText(str);
        }
    }

    class NetworkThread extends Thread {
        public void run() {
            try {
                Thread.sleep(2 * 1000);
                String str = "data from net.";
                Message msg = handler_network.obtainMessage();
                msg.obj = str;
                handler_network.sendMessage(msg);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }