Java自定义按钮paintComponent不会重新绘制默认按钮背景

Question

我正在用 Java 中的 Swing 制作一个自定义按钮。这就是我的按钮的样子:

我想要一个带有圆角的浅灰色按钮，我想稍后添加一个小图像。

问题是当我重写paintComponent()时，将绘制灰色圆形，但您会在它后面看到旧的蓝色 Swing 背景。按钮的角必须是透明的。

这是我的代码 打包游戏；

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;

import javax.swing.JButton;

public class ItemButton extends JButton {

    public ItemButton(String text) {

        super(text);
        this.setBorderPainted(false);
        this.setBorder(null);

    }

    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);

        Graphics2D g2 = (Graphics2D) g;

        g2.setColor(new Color(220, 220, 220));
        g2.fillRoundRect(0, 0, this.getWidth() - 10, this.getHeight() - 10, 10, 10);
    }

}

Answer 1

我不确定你为什么要这样做，因为 JButton 允许你提供 Icon 图像，但无论如何......

有一种方法可以使用 JButton 来做到这一点，但这不是正确的做法，相反，您应该从使用 AbstractButton 开始，因为它没有 UI首先将绘画委托(delegate)给它，例如......

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 java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.AbstractButton;
import javax.swing.DefaultButtonModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class CustomButton {

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

    public CustomButton() {
        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.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new GridBagLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends AbstractButton {

        public TestPane() {
            setModel(new DefaultButtonModel());
            MouseHandler mh = new MouseHandler();
            addMouseListener(mh);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(40, 20);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics g2d = (Graphics2D) g.create();
            g2d.setColor(new Color(220, 220, 220));
            g2d.fillRoundRect(0, 0, this.getWidth() - 1, this.getHeight() - 1, 10, 10);
            if (getModel().isRollover()) {
                g2d.setColor(new Color(128, 128, 128));
                g2d.drawRoundRect(0, 0, this.getWidth() - 1, this.getHeight() - 1, 10, 10);
            }
            g2d.dispose();
        }

        public class MouseHandler extends MouseAdapter {

            @Override
            public void mouseEntered(MouseEvent e) {
                getModel().setRollover(true);
            }

            @Override
            public void mouseExited(MouseEvent e) {
                getModel().setRollover(false);
            }

            @Override
            public void mousePressed(MouseEvent e) {
                getModel().setArmed(true);
                getModel().setPressed(true);
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                getModel().setPressed(false);
                getModel().setArmed(false);
            }

        }

    }

}