鼠标悬停在 java 中移除圆形 JButton 的透明背景

Question

一旦我将鼠标悬停在任何圆形按钮上，一个方形背景就会出现在它后面并且再也不会消失。该按钮仍可单击，而方形背景则不可单击。我还没有实现任何 MouseEvents，所以我不知道为什么会出现背景

左：点击后，中：鼠标悬停后，右：原始状态

代码示例

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

public class GUI implements ActionListener {
    private JLabel textLabel;
    private JButton buttonL, buttonConfirm, buttonR;
    
    public GUI() {
        JPanel mainDisplay = new JPanel();
        mainDisplay.setBackground(new Color(172, 181, 176));
        mainDisplay.setPreferredSize(new Dimension(150, 160));
        mainDisplay.setLayout(new BorderLayout());
        textLabel = new JLabel("1");
        textLabel.setHorizontalAlignment(SwingConstants.CENTER);
        mainDisplay.add(textLabel, BorderLayout.CENTER);
        
        JPanel container = new JPanel();
        container.setLayout(new GridBagLayout());
        GridBagConstraints gc = new GridBagConstraints();
        gc.gridwidth = GridBagConstraints.REMAINDER;
        gc.insets = new Insets(75, 0, 0, 0);
        container.add(mainDisplay, gc);
        
        Dimension buttonDimension = new Dimension(18, 18);
        Color buttonColor = new Color(242, 240, 241);
        buttonL = new RoundButton();
        buttonL.setBackground(buttonColor);
        buttonL.setPreferredSize(buttonDimension);
        buttonL.addActionListener(this);
        gc.gridwidth = GridBagConstraints.RELATIVE;
        gc.insets = new Insets(10, 20, 0, 0);
        container.add(buttonL, gc);
        
        buttonConfirm = new RoundButton();
        buttonConfirm.setBackground(buttonColor);
        buttonConfirm.setPreferredSize(buttonDimension);
        buttonConfirm.addActionListener(this);
        gc.insets = new Insets(40, -35, 0, 0);
        container.add(buttonConfirm, gc);
        
        buttonR = new RoundButton();
        buttonR.setBackground(buttonColor);
        buttonR.setPreferredSize(buttonDimension);
        buttonR.addActionListener(this);
        gc.insets = new Insets(10, -50, 0, 0);
        container.add(buttonR, gc);
        
        JFrame frame = new JFrame();
        frame.add(container);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
    
    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == buttonL) {
            textLabel.setText("L");;
        } else if(e.getSource() == buttonConfirm) {
            textLabel.setText("");
        } else if(e.getSource() == buttonR) {
            textLabel.setText("R");
        }
    }
    
    public static void main(String[] args) {        
            new GUI();
    }
}

圆形JButton

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Shape;
import java.awt.geom.Ellipse2D;
import javax.swing.JButton;

public class RoundButton extends JButton {
    Shape shape;
    
    @Override
    protected void paintComponent(Graphics g) {
        g.setColor(getBackground());
        g.fillOval(0, 0, getSize().width - 1, getSize().height - 1);
    }

    @Override
    protected void paintBorder(Graphics g) {
        g.setColor(Color.darkGray);
        g.drawOval(0, 0, getSize().width - 1, getSize().height - 1);
    }

    @Override
    public boolean contains(int x, int y) {
        if (shape == null || !shape.getBounds().equals(getBounds())) {
            shape = new Ellipse2D.Float(0, 0, getWidth(), getHeight());
        }
        return shape.contains(x, y);
    }
}

Answer 1

自定义绘画时的基本代码应该是：

public void paintComponent(Graphics g)
{
    super.paintComponent(g);

    // add custom painting here
}

这将确保背景被清除，因此没有绘画伪影。

但是，在您的情况下，您希望在绘制按钮之前先绘制父面板的背景，因此您需要使用：

button.setOpaque(false);

此外，当您单击按钮时，矩形仍会出现，表示按钮处于按下状态。要删除这幅画，您需要使用：

button.setContentAreaFilled( false );

查看：Change JButton focus area 圆形按钮的另一个实现。

鼠标悬停在 java 中移除圆形 JButton 的透明背景

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