将JLabel放在JLabel顶部，图像在

Question

我很确定以前曾问过这个问题，但是我的情况略有不同，因为我试图将JLabel放在作为背景的JLabel上，我想使用JLabel显示变化的数字，并且数字需要显示在背景上，但是我有点摇摆n00b，在此先感谢乔纳森

Answer 1

Without fully appreciating your requirements, if you simply need to display text over a background image, you'd be better off placing the label on top a custom panel which is capable of painting your background.

You get the benefit of a layout manager without the mess.

I'd start by having a read trough Performing Custom Painting and Graphics2D Trail .

If that seems to daunting, JLabel is actually a type of Container , meaning it can actually 'contain' other components.

EXAMPLE

Background pane...

public class PaintPane extends JPanel {

    private Image background;

    public PaintPane(Image image) {     
        // This is just an example, I'd prefer to use setters/getters
        // and would also need to provide alignment options ;)
        background = image;            
    }

    @Override
    public Dimension getPreferredSize() {
        return background == null ? new Dimension(0, 0) : new Dimension(background.getWidth(this), background.getHeight(this));            
    }

    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);

        if (background != null) {                
            Insets insets = getInsets();

            int width = getWidth() - 1 - (insets.left + insets.right);
            int height = getHeight() - 1 - (insets.top + insets.bottom);

            int x = (width - background.getWidth(this)) / 2;
            int y = (height - background.getHeight(this)) / 2;

            g.drawImage(background, x, y, this);                
        }

    }

}

Constructed with...

public TestLayoutOverlay() throws IOException { // Extends JFrame...

    setTitle("test");
    setLayout(new GridBagLayout());
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    PaintPane pane = new PaintPane(ImageIO.read(new File("fire.jpg")));
    pane.setLayout(new BorderLayout());
    add(pane);

    JLabel label = new JLabel("I'm on fire");
    label.setFont(label.getFont().deriveFont(Font.BOLD, 48));
    label.setForeground(Color.WHITE);
    label.setHorizontalAlignment(JLabel.CENTER);
    pane.add(label);

    pack();
    setLocationRelativeTo(null);
    setVisible(true);

}

And just to show that I'm not bias ;), an example using labels...

public TestLayoutOverlay() {

    setTitle("test");
    setLayout(new GridBagLayout());
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    JLabel background = new JLabel(new ImageIcon("fire.jpg"));
    background.setLayout(new BorderLayout());
    add(background);

    JLabel label = new JLabel("I'm on fire");
    label.setFont(label.getFont().deriveFont(Font.BOLD, 48));
    label.setForeground(Color.WHITE);
    label.setHorizontalAlignment(JLabel.CENTER);
    background.add(label);

    pack();
    setLocationRelativeTo(null);
    setVisible(true);

}

Answer 2

At runtime:

• remove the label from its parent
• add a container, which supports layers
• add the 2x layer, but keep the Z order

Enjoy. (No full code given for copy-paste)

Answer 3

you can do that by this:

JLabel l1=new JLabel();
JLabel l2=new JLabel();
l1.add(l2, JLabel.NORTH);