创建一个完全透明的 JFrame

Create a completely transparent JFrame

我有以下class

public class FileCopyManager extends JFrame{

   public static final Color TRANSPARENT_COLOR = new Color(0,0,0,0);
   public FileCopyManager(){
     this.setBackgroundColor(TRANSPARENT_COLOR);
   }
   public static void main(String[] args) {
        SwingUtilities.invokeLater(()->{
             try {
                UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel");
            }
            catch (Throwable e) {
            }
            finally{
                new FileCopyManager();
            }
         });
    }
}

然而,当我尝试 运行 这个程序时,我收到以下错误:

Exception in thread "AWT-EventQueue-0" java.awt.IllegalComponentStateException: The frame is decorated
    at java.awt.Frame.setBackground(Unknown Source)

知道为什么会这样吗?

好吧就用this.setUndecorated(true)