透明JPanel

Question

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没有正确地进行操作时.我的要求是一个半透明的Jpanel,当鼠标进入它时,此面板的边框变得可见,如果鼠标退出边框,则不可见.我通过遵循代码完成了这个,但问题是它不能正常工作的透明背景(RGBA),但它适用于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, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        final JPanel panel = new JPanel();

        panel.setBackground(new Color(0, 0, 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, 0));
        panel_1.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                panel_1.setBorder(new LineBorder(new Color(255, 255, 255), 5)); 
            }
            @Override
            public void mouseExited(MouseEvent e) {
                panel_1.setBorder(null);    
            }
        });
        panel_1.setBounds(84, 155, 215, 215);
        contentPane.add(panel_1);
    }
}

Answer 1

JPanel不支持半透明背景.处理此问题需要两个步骤:

• 首先,要有任何正确运作的透明度,你必须 setOpaque(false)在面板上; 否则你会有毛刺,因为假设一个不透明的面板完全覆盖其边界下面的东西.

• 但是,如果opaque是false,面板也根本不绘制其背景(!),因此您必须在paintComponent中绘制背景.

这是一个直接替换类,它将处理这两个步骤.

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);
    }
}

我已经检查过,如果我将第一个面板创建更改为:

final JPanel panel = new TransparentPanel();

Answer 2

它很容易做到这样:

// initialise JPanel 
JPanel somePanel = new JPanel(new GridBagLayout());
somePanel.setBackground(new Color(0,0,0,x);

在这种情况下,x是你正在寻找的透明度水平0是不可见的,100是固体.

例如:

somePanel.setBackground(new Color(0,0,0,55)

请参阅:http : //docs.oracle.com/javase/7/docs/api/java/awt/Color.html http://docs.oracle.com/javase/7/docs/api/javax/swing/JComponent html的