Undecorated JFrame shadow

问题

How do you add a shadow to a undecorated jframe?

From what I found online, you might be able to add the jframe to another black translucent window to give a shadow effect. Or somehow apply something like this to a JFrame:

    Border loweredBorder = new EtchedBorder(EtchedBorder.LOWERED);
    setBorder(loweredBorder);

Either way I just want to know the best method or maybe a completely different way of getting the same effect like extending from another class and not jframe. I'm new to Java so I might be going down the wrong direction so any advice is appreciated.

回答1:

Basically, you need to make a series of layers.

JFrame
ShadowPanel
and content...

import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;

public class ShadowWindow {

    public static void main(String[] args) {
        new ShadowWindow();
    }

    public ShadowWindow() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setUndecorated(true);
                frame.setBackground(new Color(0, 0, 0, 0));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setContentPane(new ShadowPane());

                JPanel panel = new JPanel(new GridBagLayout());
                panel.add(new JLabel("Look ma, no hands"));

                frame.add(panel);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class ShadowPane extends JPanel {

        public ShadowPane() {
            setLayout(new BorderLayout());
            setOpaque(false);
            setBackground(Color.BLACK);
            setBorder(new EmptyBorder(0, 0, 10, 10));
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
            g2d.fillRect(10, 10, getWidth(), getHeight());
            g2d.dispose();
        }
    }
}

来源：https://stackoverflow.com/questions/19105242/undecorated-jframe-shadow

标签

java

swing

jframe

Shadow