Swing paint问题

Question

我有一个自定义scrollbarUI，我画滚动条的拇指和轨迹。但是当滚动时，它保留了一些我不想要的线条。 ：

绘画代码如下：

protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) { 
    Graphics2D g2d = (Graphics2D) g; 

    GradientPaint gradient = new GradientPaint(new Point(thumbBounds.x, thumbBounds.y), gray, new   Point(thumbBounds.x + width, thumbBounds.y), white); 

    g.setColor(white); 
    g.fillRoundRect(thumbBounds.x + 1, thumbBounds.y + 1, thumbBounds.width - 3, thumbBounds.height - 1, 2, 2); 

    g2d.setPaint(gradient); 
    g2d.fillRoundRect(thumbBounds.x + 2, thumbBounds.y + 2, thumbBounds.width - 4, thumbBounds.height - 3, 3, 3); 

    //Draw middle lines: 
    if ((getMinimumThumbSize().height + 10) < thumbBounds.height) { 
     g.setColor(new Color(167, 167, 167)); 
     int w = ((thumbBounds.width > 16) ? 8 : (int) ((thumbBounds.width/2.0) + 0.5)); 
     int x = (thumbBounds.width > 0) ? (thumbBounds.x + ((thumbBounds.width - w)/2) - 1) : thumbBounds.x; 

     g.drawLine(x, (thumbBounds.y + (thumbBounds.height/2) - 3), (x + w), (thumbBounds.y + (thumbBounds.height/2) - 3)); 
     g.drawLine(x, (thumbBounds.y + (thumbBounds.height/2) - 1), (x + w), (thumbBounds.y + (thumbBounds.height/2) - 1)); 
     g.drawLine(x, (thumbBounds.y + (thumbBounds.height/2) + 1), (x + w), (thumbBounds.y + (thumbBounds.height/2) + 1)); 
    } 

    g.setColor(color_1); 
    g.drawRoundRect(thumbBounds.x, thumbBounds.y, thumbBounds.width - 2, thumbBounds.height, 2, 2); 
} 

Answer 1

您需要使用

g.drawRoundRect(..., thumbBounds.height - 1, 2, 2) 

，而不是

g.drawRoundRect(..., thumbBounds.height, 2, 2) 

012的底部边缘位于y + height，但repaint(thumbBounds)的底部边缘位于thumbBounds.y + thumbBounds.height - 1。所以1px行仍然没有重绘。