设置JLabel或其他组件透明度

来源：互联网发布：唯一网络上市编辑：程序博客网时间：2024/05/17 06:51

在Java swing中编程中可以通过重写组件的paintComponent(Graphics g)方法来达成调节组件透明度的效果，下面是我写的一个demo：

import java.awt.AlphaComposite;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.Image;import javax.swing.ImageIcon;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;public class MainFrame extends JFrame{    JPanel cp = (JPanel)this.getContentPane();    ImageLabel label;    ImageIcon icon;    JButton button;    public MainFrame(){        init();    }    public void init(){        this.setSize(500, 300);        this.setLocation(200, 100);        this.setDefaultCloseOperation(EXIT_ON_CLOSE);        this.setLayout(null);        //设置图片并调整图片的尺寸        icon = new ImageIcon(new  ImageIcon("mq.jpg").getImage()                .getScaledInstance(180, 180, Image.SCALE_DEFAULT));        label = new ImageLabel(icon);        label.setBounds(10,10,200,200);        label.setAlpha(0.5f);        cp.add(label);        this.setVisible(true);      }    public static void main(String[] args) {        new MainFrame();    }}class ImageLabel extends JLabel{    public ImageLabel(ImageIcon icon){        super.setIcon(icon);    }    private AlphaComposite cmp = AlphaComposite.getInstance(AlphaComposite.SRC_OVER,1);    private float alpha;    public void setAlpha(float alpha) {        this.alpha = alpha;        if (isVisible())   paintImmediately(getBounds());    }    @Override    protected void paintComponent(Graphics g) {        // TODO Auto-generated method stub        Graphics2D g2d = (Graphics2D)g;        g2d.setComposite(cmp.derive(alpha));        super.paintComponent(g2d);    }}

上面的例子是对一个图片的JLabel的透明度调整为50%；其他的组件也可以用类似的方法进行调整。

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