Java：为什么我的JButton被绘制在背景图像后面？

Question

这是存在问题的JPanel类：

public class EntryDialog extends JPanel{

private static final long serialVersionUID = 1L;

MainWindow         mainWindow;
Image              background;
JButton            continueresume;
JButton            newresume;
JButton            settings;
JButton            exit;

public EntryDialog(MainWindow mainWindow){

    continueresume            = new JButton("Continue resume");
    newresume                 = new JButton("New resume");
    settings                  = new JButton("Settings");
    exit                      = new JButton("Exit");
    this.mainWindow           = mainWindow;
    this.background           = Utilities.getImage("images\\entryDialogBackground.jpg", true);

    this.setLayout(null);

    //continueresume button
    continueresume.setBounds(Utilities.getScaledWidth(1150), 
            Utilities.getScaledHeight(150), 
            Utilities.getScaledWidth(500), 
            Utilities.getScaledHeight(50));

    //newresume button
    newresume.setBounds(Utilities.getScaledWidth(1150), 
            Utilities.getScaledHeight(220), 
            Utilities.getScaledWidth(500), 
            Utilities.getScaledHeight(50));

    //settings button
    settings.setBounds(Utilities.getScaledWidth(1150), 
            Utilities.getScaledHeight(290), 
            Utilities.getScaledWidth(500), 
            Utilities.getScaledHeight(50));
    //exit button
    exit.setBounds(Utilities.getScaledWidth(1150), 
            Utilities.getScaledHeight(360), 
            Utilities.getScaledWidth(500), 
            Utilities.getScaledHeight(50));

    this.add(continueresume);
    this.add(newresume);
    this.add(settings);
    this.add(exit);

}

@Override
public void paintComponent(Graphics g){
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g;
    if(background != null){
        g2d.drawImage(background, 0, 0, this);
    }
    g2d.dispose();
}

将此JPanel绘制到另一类的主框架上。发生的是“背景”被很好地绘制，但按钮却没有。一旦我将鼠标悬停在按钮上，这些按钮就会出现，但直到那时它们都是不可见的。我已经搜索了几个小时，还没有找到解决方案，所以我们将不胜感激。谢谢！

Answer 1

我不得不猜测它正在您的paintComponent方法中发生。您正在调用super.paintComponent（）会像平常一样绘制所有内容，包括按钮。然后，使用g2d.drawImage（）对其进行绘制。您应该先绘制背景。