这个可以吗?
它还远非完美,但基本思路可行...
public class MyRoundedBorder implements Border {
protected static final Insets DEFAULT_INSETS = new Insets(4, 4, 4, 4);
@Override
public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.setStroke(new BasicStroke(3, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
g2d.setColor(Color.WHITE);
Shape corner = new RoundedShape(width - 8, height - 8);
g2d.translate(x + 2, y + 2);
g2d.draw(corner);
g2d.transform(AffineTransform.getRotateInstance(Math.toRadians(180), (width - 8) / 2, (height - 8) / 2));
g2d.setColor(Color.LIGHT_GRAY);
g2d.draw(corner);
g2d.dispose();
}
@Override
public Insets getBorderInsets(Component c) {
return DEFAULT_INSETS;
}
@Override
public boolean isBorderOpaque() {
return true;
}
public class RoundedShape extends Path2D.Float {
public RoundedShape(int width, int height) {
moveTo(0, height - 20);
append(new Arc2D.Float(0, height - 20, 20, 20, 180, 45, Arc2D.CHORD), false);
lineTo(0, 20);
curveTo(0, 0, 0, 0, 20, 0);
lineTo(width - 10, 0);
append(new Arc2D.Float(width - 20, 0, 20, 20, 90, -45, Arc2D.CHORD), false);
}
}
}