"Only the original thread that created a view hierarchy can touch its views." SOLUTION

View components in Android are NOT thread-safe. to update a view, they must be updated in the main thread. Update operations cannot be performed in subthreads. Therefore, the message mechanism can be used for updates.

Declare a handler to process the message first.

 private Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {                setContentView(child);        }    };

Then, send a message to handler in the method of the event triggered in the view to trigger the update view.

        b2 = (Button) findViewById(R.id.return_button);        b2.setOnClickListener(new Button.OnClickListener() {            public void onClick(View v) {                setWebView();            }        });    

　　

    private void setWebView() {        Message msg = new Message();        msg.what = CHANGE_WEB;        handler.sendMessage(msg);    }

In this way, you can operate the main view in other threads.

 

"Only the original thread that created a view hierarchy can touch its views." SOLUTION