我只需要在组件的一侧创建圆角边框。
这段代码创建了一个圆形边框：
new LineBorder(Color.RED, 3, true)
我见过this thread，它向您展示了如何创建只能在组件的一侧使用的哑光边框，但哑光边框不是圆角的。
是否可以只在一侧有圆形边框？
编辑：
我尝试过像这样使用复合边框：
cell.setBorder(BorderFactory.createCompoundBorder(
new LineBorder(borderColor, 3, true),
BorderFactory.createMatteBorder(0, 3, 0, 0, Color.black)));
但它不起作用......
【问题讨论】：
您可以覆盖 LineBorder 的方法并在那里绘制您需要的所有内容 来自 LineBorder 的来源
public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
Color oldColor = g.getColor();
int i;
/// PENDING(klobad) How/should do we support Roundtangles?
g.setColor(lineColor);
for(i = 0; i < thickness; i++) {
if(!roundedCorners)
g.drawRect(x+i, y+i, width-i-i-1, height-i-i-1);
else
SET CLIP HERE TO DRAW ONLY NECESSARY PART
g.drawRoundRect(x+i, y+i, width-i-i-1, height-i-i-1, thickness, thickness);
}
g.setColor(oldColor);
}
【讨论】：
g.drawRoundRect(...) 似乎并不简单，IMO。但这是一个开始 - 您必须分别绘制圆角和边缘。
LineBorder 只支持圆角与否。复合边框（如 JavaDoc 所述）使用一个边框作为外部边框，一个边框作为内部边框，因此不区分左/右或上/下。
恐怕您要么必须编写自己的 Border 实现，要么寻找其他人已经制作的实现（外部库）。
【讨论】：
这是一个关于如何使用Graphics2D#clipRect() 的示例。
此代码仅保留两个右圆角，并在左侧具有正常边框。如上所述，您必须在自定义 LineBorder 中使用此代码。
Graphics2D g2d = (Graphics2D) g;
g2d.clipRect(150, 10, 100, 100);
g2d.draw(new RoundRectangle2D.Double(100, 10, 80, 30, 15, 15));
g2d.setClip(null);
g2d.clipRect(100, 10, 50, 100);
g2d.draw(new Rectangle2D.Double(100, 10, 80, 30));
【讨论】：
public static final int TOP_LEFT = 1;
public static final int TOP_RIGHT = 2;
public static final int BOTTOM_LEFT = 4;
public static final int BOTTOM_RIGHT = 8;
public static final int ALL_CORNERS = TOP_LEFT + TOP_RIGHT + BOTTOM_LEFT + BOTTOM_RIGHT;
public static void drawRoundRect(Graphics g, Color fillColor, Color borderColor, int x, int y, int width, int height, int radius, int cornerMask)
{
// // XXX Old code (without selectively disabled round corners):
// if (fillColor != null)
// {
// og.setColor(fillColor);
// og.fillRoundRect(x, y, width - 1, height - 1, radius, radius);
// }
// if (borderColor != null && !borderColor.equals(fillColor))
// {
// og.setColor(borderColor);
// og.drawRoundRect(x, y, width - 1, height - 1, radius, radius);
// }
radius += radius % 2; // so we don't have to deal with rounding issues for odd numbers
int radiusHalf = radius / 2;
width--;
height--;
if (fillColor != null)
{
g.setColor(fillColor);
// og.fillRoundRect(x, y, width - 1, height - 1, radius, radius);
if ((cornerMask & TOP_LEFT) > 0)
{
g.fillArc(x, y, radius, radius, 90, 90);
}
else
{
g.fillRect(x, y, radiusHalf, radiusHalf);
}
if ((cornerMask & TOP_RIGHT) > 0)
{
g.fillArc(x + width - radius, y, radius, radius, 0, 90);
}
else
{
g.fillRect(x + width - radiusHalf, y, radiusHalf, radiusHalf);
}
if ((cornerMask & BOTTOM_RIGHT) > 0)
{
g.fillArc(x + width - radius, y + height - radius, radius, radius, 270, 90);
}
else
{
g.fillRect(x + width - radiusHalf, y + height - radiusHalf, radiusHalf, radiusHalf);
}
if ((cornerMask & BOTTOM_LEFT) > 0)
{
g.fillArc(x, y + height - radius, radius, radius, 180, 90);
}
else
{
g.fillRect(x, y + height - radiusHalf, radiusHalf, radiusHalf);
}
g.fillRect(x + radiusHalf, y, width - radius, radiusHalf);
g.fillRect(x + radiusHalf, y + height - radiusHalf, width - radius, radiusHalf);
g.fillRect(x, y + radiusHalf, radiusHalf, height - radius);
g.fillRect(x + width - radiusHalf, y + radiusHalf, radiusHalf, height - radius);
g.fillRect(x + radiusHalf, y + radiusHalf, width - radius, height - radius);
}
if (borderColor != null && !borderColor.equals(fillColor))
{
g.setColor(borderColor);
// XXX: there are problems with this when using semi-transparent colors + borderSize > 1
// XXX: this could be changed to to use ONE draw action using drawShape with GeneralPath.curveTo()
// XXX: this then could also be used to FILL the shape (see above)
if ((cornerMask & TOP_LEFT) > 0)
{
g.drawArc(x, y, radius, radius, 90, 90);
}
else
{
g.drawLine(x, y, x + radiusHalf, y);
g.drawLine(x, y, x, y + radiusHalf);
}
if ((cornerMask & TOP_RIGHT) > 0)
{
g.drawArc(x + width - radius, y, radius, radius, 0, 90);
}
else
{
g.drawLine(x + width - radiusHalf, y, x + width, y);
g.drawLine(x + width, y, x + width, y + radiusHalf);
}
if ((cornerMask & BOTTOM_RIGHT) > 0)
{
g.drawArc(x + width - radius, y + height - radius, radius, radius, 270, 90);
}
else
{
g.drawLine(x + width - radiusHalf, y + height, x + width, y + height);
g.drawLine(x + width, y + height - radiusHalf, x + width, y + height);
}
if ((cornerMask & BOTTOM_LEFT) > 0)
{
g.drawArc(x, y + height - radius, radius, radius, 180, 90);
}
else
{
g.drawLine(x, y + height, x + radiusHalf, y + height);
g.drawLine(x, y + height - radiusHalf, x, y + height);
}
g.drawLine(x + radiusHalf, y, x + width - radiusHalf, y); // top
g.drawLine(x + width, y + radiusHalf, x + width, y + height - radiusHalf); // right
g.drawLine(x + radiusHalf, y + height, x + width - radiusHalf, y + height); // bottom
g.drawLine(x, y + radiusHalf, x, y + height - radiusHalf); // left
}
}
【讨论】：
这是一个例子，
JPanel content = new JPanel();
content.setBorder(BorderFactory.createEmptyBorder(1,30,1,1));
【讨论】：