Java JScrollBar自定义滚动条ui图形留下痕迹

我正在做一个定制的JScrollBar

ScrollBar.java

public class ScrollBar extends JScrollBar {
    ScrollBar() {
        super();
        setUI(new CustomScrollBarUI());
    }
}

public class CustomScrollBarUI extends BasicScrollBarUI {
    @Override
    protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g.setColor(Color.BLACK);
        g2d.fill(trackBounds);
        g2d.draw(trackBounds);
    }
    @Override
    protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.WHITE);
        g2d.fill(thumbBounds);
        g2d.draw(thumbBounds);
    }
}

public class CustomScrollBarUI extends BasicScrollBarUI {
    @Override
    protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g.setColor(Color.BLACK);
        g2d.fill(trackBounds);
        g2d.draw(trackBounds);
    }
    @Override
    protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.WHITE);
        g2d.fill(thumbBounds);
//      g2d.draw(thumbBounds);
    }
}

CustomScrollBarUI.java

public class ScrollBar extends JScrollBar {
    ScrollBar() {
        super();
        setUI(new CustomScrollBarUI());
    }
}

public class CustomScrollBarUI extends BasicScrollBarUI {
    @Override
    protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g.setColor(Color.BLACK);
        g2d.fill(trackBounds);
        g2d.draw(trackBounds);
    }
    @Override
    protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.WHITE);
        g2d.fill(thumbBounds);
        g2d.draw(thumbBounds);
    }
}

public class CustomScrollBarUI extends BasicScrollBarUI {
    @Override
    protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g.setColor(Color.BLACK);
        g2d.fill(trackBounds);
        g2d.draw(trackBounds);
    }
    @Override
    protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.WHITE);
        g2d.fill(thumbBounds);
//      g2d.draw(thumbBounds);
    }
}

但是，向下滚动时会留下白色痕迹，向上滚动时会清除

我试过很多东西

添加

super.method（）

所以我将

super.paintThumb（g，c，thumbBounds）

和

super.paintrack（g，c，trackBounds）

添加到这两个函数中，但没有任何更改

清除上一个矩形

添加了一组变量来存储以前的位置

double last_posx = -1d;
double last_posy = -1d;
double last_posw = -1d;
double last_posh = -1d;

然后清除上一个矩形

if (last_posx != -1d) {
    g.clearRect((int) last_posx, (int) last_posy, (int) last_posw, (int) last_posh);
}

这会导致效果增加更多，因此会留下更多的白色

重新粉刷轨道

这一次我想到了我自己。因此，我添加了

super.paintTrack（g，c，super.getTrackBounds（））

在绘制拇指之前重新绘制轨迹，以尝试清除之前的拇指

这产生了与1相同的效果

那么我该怎么做才能清除留下的白色痕迹呢

编辑

正如LuxxMiner提到的，这解决了问题，但我想知道为什么

CustomScrollBarUI.java

public class ScrollBar extends JScrollBar {
    ScrollBar() {
        super();
        setUI(new CustomScrollBarUI());
    }
}

public class CustomScrollBarUI extends BasicScrollBarUI {
    @Override
    protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g.setColor(Color.BLACK);
        g2d.fill(trackBounds);
        g2d.draw(trackBounds);
    }
    @Override
    protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.WHITE);
        g2d.fill(thumbBounds);
        g2d.draw(thumbBounds);
    }
}

public class CustomScrollBarUI extends BasicScrollBarUI {
    @Override
    protected void paintTrack(Graphics g, JComponent c, Rectangle trackBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g.setColor(Color.BLACK);
        g2d.fill(trackBounds);
        g2d.draw(trackBounds);
    }
    @Override
    protected void paintThumb(Graphics g, JComponent c, Rectangle thumbBounds) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.WHITE);
        g2d.fill(thumbBounds);
//      g2d.draw(thumbBounds);
    }
}

---

我不知道为什么，但是删除了

g2d.draw（thumbunds）为我修复了它…是的，这也为我修复了轨迹。也许它自己画出了指界？