Java swing实现圆角方框

要在 Java Swing 中实现圆角方框的效果，可以通过设置组件的 Border 来实现。可以自定义一个 Border 类来实现圆角方框的效果。具体方法如下：

1. 创建一个 RoundedBorder 类，该类继承 javax.swing.border.AbstractBorder 类，并实现其中的 paintBorder() 方法。

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Insets;

import javax.swing.border.AbstractBorder;

public class RoundedBorder extends AbstractBorder {
    private static final long serialVersionUID = 1L;
    private Color borderColor;
    private int borderRadius;

    public RoundedBorder(Color borderColor, int borderRadius) {
        this.borderColor = borderColor;
        this.borderRadius = borderRadius;
    }

    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
        g.setColor(borderColor);
        g.drawRoundRect(x, y, width - 1, height - 1, borderRadius, borderRadius);
    }

    public Insets getBorderInsets(Component c) {
        return new Insets(borderRadius + 1, borderRadius + 1, borderRadius + 2, borderRadius);
    }

    public Insets getBorderInsets(Component c, Insets insets) {
        insets.left = borderRadius + 1;
        insets.right = borderRadius + 1;
        insets.top = borderRadius + 2;
        insets.bottom = borderRadius;
        return insets;
    }

    public boolean isBorderOpaque() {
        return true;
    }

    public int getBorderRadius() {
        return borderRadius;
    }

    public void setBorderRadius(int borderRadius) {
        this.borderRadius = borderRadius;
    }

    public Color getBorderColor() {
        return borderColor;
    }

    public void setBorderColor(Color borderColor) {
        this.borderColor = borderColor;
    }
}

2. 在需要添加圆角方框的组件上设置 RoundedBorder。

JPanel panel = new JPanel();
panel.setBackground(Color.WHITE);
RoundedBorder roundedBorder = new RoundedBorder(Color.GRAY, 20);
panel.setBorder(roundedBorder);

通过设置 RoundedBorder 类的 borderRadius 属性，可以调整圆角的大小。