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();
}