java – 透明JPanel

我想创建一个半透明的JPanel.我通过简单地使用颜色构造函数的RGBA值来完成它,但问题是当我使用事件处理不正确地唤醒时.我的要求是一个半透明的Jpanel,当鼠标进入它的边框,这个面板变得可见,如果鼠标退出边框不可见.我已经通过以下代码做到这一点,但问题是它不能正常工作的透明背景(RGBA),但它可以正常工作的RGB颜色.

import javax.swing.*;
import javax.swing.border.*;
import java.awt.*;
import java.awt.event.*;

public class MDCW extends JFrame {

      private JPanel contentPane;

     /**
     * Launch the application.
     */
     public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    MDCW frame = new MDCW();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public MDCW() {
        setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100,100,1013,551);
        contentPane = new JPanel();
        contentPane.setBackground(new Color(0,139,139));
        contentPane.setBorder(new EmptyBorder(5,5,5));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        final JPanel panel = new JPanel();

        panel.setBackground(new Color(0,50));
        panel.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                panel.setBorder(new LineBorder(new Color(255,255,255),5));   
            }
            @Override
            public void mouseExited(MouseEvent e) {
                panel.setBorder(null);  
            }
        });
        panel.setBounds(360,155,215,215);
        contentPane.add(panel);

        final JPanel panel_1 = new JPanel();
        panel_1.setBackground(new Color(0,0));
        panel_1.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                panel_1.setBorder(new LineBorder(new Color(255,5)); 
            }
            @Override
            public void mouseExited(MouseEvent e) {
                panel_1.setBorder(null);    
            }
        });
        panel_1.setBounds(84,215);
        contentPane.add(panel_1);
    }
}

private class TransparentPanel extends JPanel {
    {
        setOpaque(false);
    }
    public void paintComponent(Graphics g) {
        g.setColor(getBackground());
        Rectangle r = g.getClipBounds();
        g.fillRect(r.x,r.y,r.width,r.height);
        super.paintComponent(g);
    }
}

final JPanel panel = new TransparentPanel();