如何让 JLabel 在不可见时消耗空间？

Question

我有一个程序可以创建 2 个面板，然后在其中放置一个标签和两个按钮。将标签设置为不可见setVisible(false)，然后添加两个按钮并打包框架。当我单击第一个按钮时，显示标签，setVisible(true)，第二个按钮再次隐藏它，setVisible(false)。当我单击每个按钮时，它们会移动以填充标签隐藏的空间，然后再次移动以避开显示的标签。我想阻止这种情况发生，即使标签被隐藏，按钮也保持在同一个位置。

这是代码：

public class MainFrame extends JFrame{
  public JLabel statusLabel;
  public JButton show;
  public JButton hide;  

  public MainFrame(){
    super("MagicLabel");

    JPanel topPanel = new JPanel();  //Create Top Panel
    statusLabel = new JLabel("");    //Init label
    statusLabel.setVisible(false);   //Hide label at startup
    topPanel.setSize(400, 150);      //Set the size of the panel, Doesn't work
    topPanel.add(statusLabel);       //Add label to panel

    JPanel middlePanel = new JPanel(); //Create Middle Panel
    show= new JButton("Show");       //Create show button
    hide= new JButton("Hide");       //Create hide button
    middlePanel.setSize(400, 50);    //Set the size of the panel, Doesn't work
    middlePanel.add(show);           //Add show button
    middlePanel.add(hide);           //Add hide button

    this.add(topPanel, "North");     //Add Top Panel to North
    this.add(middlePanel, "Center"); //Add Middle Panel to Center
    addActionListeners();            //void:adds action listeners to buttons
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setBounds(100, 100, 512, 400);
    this.setPreferredSize(new Dimension(400,200)); //Set size of frame, Does work
    this.pack();
    this.setVisible(true);
  }

  public void animateInstall(boolean var0){  //Void to show and hide label from action listeners
    statusLabel.setVisible(var0);
    sendWorkingMessage("Boo!");
  }
  public void sendWorkingMessage(String message){ //Void to set text of label
    this.statusLabel.setForeground(new Color(225, 225, 0));
    this.statusLabel.setText(message);
  }

  void addActionListeners(){
    show.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            animateInstall(true);
        }
    });
    hide.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            animateInstall(false);
        }
    });
  }

Answer 1

this.setPreferredSize(new Dimension(400,200));
this.setMinimumSize(new Dimension(400,200));

所以pack()不能干涉。