java - 如果我注释了一些代码，JButton 就会消失

Question

如果我对代码进行注释，JButtons 就会消失

public class analisi_spesa {

public static void main(String[] args) {

    JFrame mainFrame = new JFrame("Java SWING Examples");
    mainFrame.setSize(400,400);
    mainFrame.setLayout(new GridLayout(3, 1));
/*
    JLabel headerLabel = new JLabel("headerLabel",JLabel.CENTER );
    JLabel statusLabel = new JLabel("statusLabel",JLabel.CENTER);        
    statusLabel.setSize(350,100);
*/
    mainFrame.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
        }        
    });    

    JPanel controlPanel = new JPanel();
    controlPanel.setLayout(new FlowLayout());
/*
    mainFrame.add(headerLabel);
    mainFrame.add(controlPanel);
    mainFrame.add(statusLabel);
*/  


    mainFrame.setVisible(true); 

//          headerLabel.setText("Control in action: Button");



    JButton okButton = new JButton("OK");
    JButton submitButton = new JButton("Submit");
    JButton cancelButton = new JButton("Cancel");

    okButton.setActionCommand("OK");
    submitButton.setActionCommand("Submit");
    cancelButton.setActionCommand("Cancel");

    okButton.addActionListener(new ButtonClickListener()); 
    submitButton.addActionListener(new ButtonClickListener()); 
    cancelButton.addActionListener(new ButtonClickListener()); 

    controlPanel.add(okButton);
    controlPanel.add(submitButton);
    controlPanel.add(cancelButton);       

    mainFrame.setVisible(true);

}

}

我希望它们能显示出来，因为我没有对代码进行注释。我从 https://www.tutorialspoint.com/swing/swing_event_handling.htm 中拿了这个例子谢谢大家，我在等待答案。

Answer 1

不要评论这部分:

mainFrame.add(controlPanel);

因为以后你会做

controlPanel.add(okButton);
controlPanel.add(submitButton);
controlPanel.add(cancelButton); 

因此您将所有按钮添加到“controlPanel”但是如果你不添加 controlPanel 到你的 mainFrame，按钮将不会显示