android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a vi

今天继续在编写app，后来女朋友来消息，按了home将app后台运行，再打开时崩了，

，报了如下错误：

 android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

大致意思就是，我在非主线程更新ui了，所以崩了

（真特么低级的错误，去年犯的错今年还犯）

private  void setdate() {
    new Thread(new Runnable() {
        @Override

        public void run() {
            String strURL = "http://jirenguapi.applinzi.com/weather.php";
            URL url = null;
            try {
                url = new URL(strURL);

                HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
                InputStreamReader input = new InputStreamReader(httpConn
                        .getInputStream(), "utf-8");
                BufferedReader bufReader = new BufferedReader(input);
                String line = "";
                StringBuilder contentBuf = new StringBuilder();
                while ((line = bufReader.readLine()) != null) {
                    contentBuf.append(line);
                }
                date_weather.setText(contentBuf);
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();

            }

        }
    }).start();
}

改成如下代码，使用了handler异步更新，测试后不再崩溃，大致原理是在主线程创了一个handler，接收来自子线程的数据并更新ui

private Handler 
handler_setdate =  new Handler()
{
    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        String message = msg.obj.toString();
        date_weather.setText(message);


    }

};
private  void setdate() {
    new Thread(new Runnable() {
        @Override

        public void run() {
            String strURL = "http://jirenguapi.applinzi.com/weather.php";
            URL url = null;
            try {
                url = new URL(strURL);

                HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
                InputStreamReader input = new InputStreamReader(httpConn
                        .getInputStream(), "utf-8");
                BufferedReader bufReader = new BufferedReader(input);
                String line = "";
                StringBuilder contentBuf = new StringBuilder();
                while ((line = bufReader.readLine()) != null) {
                    contentBuf.append(line);
                }
                Message msg = new Message();
                msg.obj= contentBuf;
                handler_setdate.sendMessage(msg);
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();

            }

        }
    }).start();
}