java - 为什么我需要将鼠标悬停在按钮上才能显示？

Question

我在这里遇到了一个问题，我的按钮工作正常，直到我添加了背景图像，当我尝试将鼠标放在按钮和文本字段上以显示它们时。我的标签也不起作用，无论我的鼠标是点击它还是点击它？这是该类的代码。

public class launcher extends JFrame{
    private static final long serialVersionUID = 1L;

     protected JPanel window = new JPanel();
     protected JFrame f = new JFrame("stackoverflow");

    private Rectangle rAncient, rMedieval, rModern, rFuture, rFinancial, rUpdate;
    private JButton ancient, medieval, modern, future, financial, update;
    private JLabel time, name;
    private JTextField tName;


     protected int width = 600;
     protected int height = 400;
     protected int button_width = 80;
     protected int button_height = 40;


    public launcher(int id) throws IOException{
        try{
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (Exception e){
            e.printStackTrace();
        }
        setTitle("Choose your Path");
        setSize(new Dimension(width, height));
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        getContentPane().add(window);
        setLocationRelativeTo(null);
        setResizable(false);
        setVisible(true);
        window.setLayout(null);
        if(id==0){
        drawButtons();
    }
        repaint();
    }
    private void drawButtons(){
        ancient = new JButton("Ancient");
        rAncient = new Rectangle(140, 150, 70, 40);
        ancient.setBounds(rAncient);
        window.add(ancient);

        medieval = new JButton("Medieval");
        rMedieval = new Rectangle(220, 150, 80, 40);
        medieval.setBounds(rMedieval);
        window.add(medieval);

        modern = new JButton("Modern");
        rModern = new Rectangle(310, 150, 70, 40);
        modern.setBounds(rModern);
        window.add(modern);

        future = new JButton("Future");
        rFuture = new Rectangle(350, 150, 70, 40);
        future.setBounds(rFuture);
        window.add(future);

        financial = new JButton("Financial");
        rFinancial = new Rectangle(390, 150, 70, 40);
        future.setBounds(rFinancial);
        window.add(financial);

        update = new JButton("Update");
        rUpdate = new Rectangle(250, 300, 100, 50);
        update.setBounds(rUpdate);
        window.add(update);

        time = new JLabel("Choose your desired time period");
        time.setBounds(220, 90, 200, 50);
        window.add(time);

        name = new JLabel("Name: ");
        name.setBounds(210, 220, 200, 50);
        window.add(name);

        tName = new JTextField();
        tName.setBounds(250, 235, 150, 20);
        window.add(tName);
        tName.setText("Bob");

          ancient.addActionListener(new ActionListener(){

            public void actionPerformed(ActionEvent a){
                System.out.println("Starting in Ancient mode...");
            }
          });

          medieval.addActionListener(new ActionListener(){

            public void actionPerformed(ActionEvent a){
                System.out.println("Starting in Medieval mode...");
            }
          });

          modern.addActionListener(new ActionListener(){

            public void actionPerformed(ActionEvent a){
                System.out.println("Starting in Modern mode...");
            }
          });

          future.addActionListener(new ActionListener(){

            public void actionPerformed(ActionEvent a){
                System.out.println("Starting in Future mode...");
            }
          });

          financial.addActionListener(new ActionListener(){

            public void actionPerformed(ActionEvent a){
                System.out.println("Starting in Financial mode...");
            }
          });

          update.addActionListener(new ActionListener(){

            public void actionPerformed(ActionEvent a){
                System.out.println("Opening browser to http://ubergamesproductions.weebly.com/adventure");
                try{
                    String URL ="http://ubergamesproductions.weebly.com/adventure";
                    java.awt.Desktop.getDesktop().browse(java.net.URI.create(URL));
                }catch(Exception e){
                    JOptionPane.showMessageDialog(null, e.getMessage());
                }
            }
          });
    }
    public static void main(String[] args)throws IOException{
    new launcher(0);
    }
      private Image backgroundImage = ImageIO.read(new File("C:/Users/Samuels Laptop/Dropbox/Java/Questor/Launcher_UGP.png"));
      public void paint(Graphics g) { 
        super.paint(g);
        g.drawImage(backgroundImage, 0, 0, null);
      }
};

Answer 1

public launcher(int id) throws IOException{

使用标准的 Java 命名约定。类名应以大写字符开头。

window.setLayout(null);
...
ancient = new JButton("Ancient");
rAncient = new Rectangle(140, 150, 70, 40);
ancient.setBounds(rAncient);

不要使用空布局和 setBounds(...)。使用合适的布局管理器并让布局管理器完成它的工作。在这种情况下，您可能可以使用 JPanel 及其默认的 FlowLayout。

public void paint(Graphics g) { 
    super.paint(g);
    g.drawImage(backgroundImage, 0, 0, null);

不要覆盖顶级容器的 paint() 方法。在您的情况下，您的代码绘制了框架和所有组件。然后你绘制图像。所以图像覆盖了组件。该按钮响应 mouseEntered 事件以 repaint() 边框，​​这就是它突然出现的原因。

相反，自定义绘画是通过覆盖 JPanel 的 paintComponent(...) 方法来完成的。然后将面板添加到框架并将组件添加到面板。阅读 Custom Painting 上的 Swing 教程部分了解更多信息。花时间阅读整个教程。还有一个关于 Layout Managers 的部分。