有没有一种方法可以在不使用JLabel或Overrideing paintComponent的情况下向JPanel添加背景图像？

Question

I want to add background image to JPanel without using JLabel or overriding paintComponent.

JPanel don't have setIcon(ImageIcon). I really want to dynamically change the background image of JPanel like setIcon in other component like JLabel.

Answer 1

"I want to add background image to JPanel without using JLabel or overriding paintComponent"

Seems like a bit of a stretch. You want to do something, but you don't to do it the way it's supposed to be done. Maybe a better understanding of how this can be accomplished will make you change your mind.

JPanel and override paintComponent

Have a method to setImage(Image image) or you can use ImageIcon , up to you. You can set the image that is used to paint the background.

public class BackgroundPanel extends JPanel {
    private Image image;

    public void setImage(Image image) {
        this.image = image;
        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0 getWidth(), getHeight(), this);
    }
}

When you call setImage passing it an image, it will dynamically change the image, because of the call to repaint()

Using JLabel

As nIcE cOw mentioned, you can use the JLabel as the container, and add all your components to the label. Remember JLabel is a subclass of Container. Any Container can be added to. Just keep in mind that JLabel has no layout manager (unlike JFrame and JPanel which has defaults), so you need to set it. You could simply do something like

JLabel backgroundLabel = new JLabel();
backgroundLabel.setIcon(new ImageIcon("backgound.png"));
backgroundLabel.setLayout(new GridBagLayout());
backgroundLabel.add(new JButton("Hello World"));

That's perfectly legal.

Another Alternative

A class from Sir Rob Camick BackgroundPanel . Check out the link for how to use it. It's basically the same concept as the first option I described, just 100 times better with a whole lot more goodies.