设置 JFrame 背景透明但显示内容

Question

我正在寻找一些解决方案，将不透明的空 JFrame 背景变为透明（无半透明），但显示按钮容器等摆动组件... 这里是一个例子。

默认的 JFrame

类似，这里禁用背景

Answer 1

这是一个简单的两步过程...

首先，你需要制作一个透明的框架...

JFrame frame = new JFrame("Testing");
frame.setUndecorated(true);
frame.setBackground(new Color(0, 0, 0, 0));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);

对于您想要透视的每个组件，您需要确保将其设置为透明，例如...

public class TestPane extends JPanel {

    public TestPane() {
        setOpaque(false);
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.insets = new Insets(4, 4, 4, 4);
        add(new JLabel("Product"), gbc);
        gbc.gridy++;
        add(new JLabel("Company"), gbc);
        gbc.gridy++;
        add(new JLabel("Phone"), gbc);

        gbc.gridx++;
        gbc.gridy = 0;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        add(new JTextField(10), gbc);
        gbc.gridy++;
        add(new JComboBox(), gbc);
        gbc.gridy++;
        add(new JTextField(10), gbc);

        JPanel buttons = new JPanel();
        buttons.setOpaque(false);
        buttons.add(new JButton("Add"));
        buttons.add(new JButton("Update"));
        buttons.add(new JButton("Delete"));
        gbc.gridx = 0;
        gbc.gridy++;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        add(buttons, gbc);

        gbc.gridy++;
        JPanel filler = new JPanel();
        filler.setBorder(new CompoundBorder(new LineBorder(Color.BLACK), new EmptyBorder(10, 10, 10, 10)));
        add(filler, gbc);

        gbc.gridy++;
        gbc.fill = GridBagConstraints.BOTH;
        add(new JScrollPane(new JTable(new DefaultTableModel(new String[]{"Product", "Company", "Phone"}, 0))), gbc);

    }

}

还有一个可运行的例子……

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;
import javax.swing.table.DefaultTableModel;

public class Test {

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

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

                JFrame frame = new JFrame("Testing");
                frame.setUndecorated(true);
                frame.setBackground(new Color(0, 0, 0, 0));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setOpaque(false);
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.insets = new Insets(4, 4, 4, 4);
            add(new JLabel("Product"), gbc);
            gbc.gridy++;
            add(new JLabel("Company"), gbc);
            gbc.gridy++;
            add(new JLabel("Phone"), gbc);

            gbc.gridx++;
            gbc.gridy = 0;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            add(new JTextField(10), gbc);
            gbc.gridy++;
            add(new JComboBox(), gbc);
            gbc.gridy++;
            add(new JTextField(10), gbc);

            JPanel buttons = new JPanel();
            buttons.setOpaque(false);
            buttons.add(new JButton("Add"));
            buttons.add(new JButton("Update"));
            buttons.add(new JButton("Delete"));
            gbc.gridx = 0;
            gbc.gridy++;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            add(buttons, gbc);

            gbc.gridy++;
            JPanel filler = new JPanel();
            filler.setBorder(new CompoundBorder(new LineBorder(Color.BLACK), new EmptyBorder(10, 10, 10, 10)));
            add(filler, gbc);

            gbc.gridy++;
            gbc.fill = GridBagConstraints.BOTH;
            add(new JScrollPane(new JTable(new DefaultTableModel(new String[]{"Product", "Company", "Phone"}, 0))), gbc);

        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.dispose();
        }

    }

}

这也是“假”半透明框架的好方法......

public class TestPane extends JPanel {

    //...

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setColor(getBackground());
        g2d.setComposite(AlphaComposite.SrcOver.derive(0.5f));
        g2d.fillRect(0, 0, getWidth(), getHeight());
        g2d.dispose();
    }

}