要更新JFrame，您必须使用

To update a JFrame you must use

revalidate(); 
repaint();

因此，在GUI中进行任何更改后，您都需要revalidate()JFrame，然后重新绘制其内容.

So after you change anything in your GUI you would want to revalidate() the JFrame and then repaint the contents of it.

祝你好运！