Program compiles, but won't run

Question

Let's keep it simple. My code compiles, and when I run it (using java CLASSNAME ), this is my command prompt error:

Exception in thread "main" java.awt.IllegalComponentStateException: The frame is
decorated
        at java.awt.Frame.setBackground(Frame.java:986)
        at RPG.<init>(RPG.java:147)
        at RPG.main(RPG.java:69)

For reference, this is the code at line 147

    Map.setBackground(new Color(0,0,0,0));

And the code at line 69

    Game.setContentPane(new RPG());

They are two different JFrames, but they are conflicting? Here is the entire snippet from my source:

  public static void main(String[] args) {
    try {
  UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
  }
  catch (Exception unused) {  }
  Game.setTitle(" ");
  Game.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  Game.setContentPane(new RPG());
  Game.setDefaultLookAndFeelDecorated(true);
  Game.pack();
  Game.setSize(850,500);
  Game.setLocationRelativeTo(null);
  Game.setResizable(false);
} 
  public RPG(){
    sgame = 1;
    Game.setVisible(false);
    JFrame Map = new JFrame();
      Map.setTitle("Map");
      Map.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      Map.setBackground(new Color(0,0,0,0));
  Map.setUndecorated(true);
  JLabel testLabel = new JLabel(new ImageIcon(getClass().getResource("Title.png")));
      Map.add(testLabel);
      Map.setSize(200,200);
      Map.setLocation(0, 250);
      Map.setResizable(false);
      Map.setVisible(true);
    Launcher();
  }

Sorry if it seems unclear or if I am not making much sense, I'd just like to know why I can't launch my program.

Answer 1

在调用.setBackground（）之前，尝试将Map设置为Undecorated。