PaintComponent() 正在其他组件上绘图

我正在使用基于中的代码的自定义类这个答案 https://stackoverflow.com/a/16909994/5686799，绘制一个形状像讲话泡泡的背景。每当我将应用程序的窗口大小调整到足以使组件在顶部或底部突出时，该组件的轮廓就会绘制在窗口之外JScrollPane在其他组件之上；在这种情况下JPanel.

在左侧图像中，组件底部的边框JScrollPane由于组件仍然可见，因此被绘制；而在右侧图像中，所提到的组件不再可见，并且一切看起来都按预期进行。

我相信这与我使用的事实有关JScrollPane包含组件，从而允许组件在JPanel。我该如何防止这种情况？

Main:

public class Main {
    public static void main(String[] args) {
        JPanel panel = new JPanel(), panelbar = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        panelbar.setLayout(new FlowLayout());

        JScrollPane scroll = new JScrollPane(panel,
                JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

        JFrame frame = new JFrame("");
        frame.setLayout(new BorderLayout());
        frame.setSize(200, 223);

        for (int i = 0; i < 6; i++) {
            JLabel label = new JLabel("JLabel");
            label.setBorder(new CustomBorder());
            label.setOpaque(true);
            label.setBackground(Color.ORANGE);
            panel.add(label);
        }

        panelbar.add(new JLabel("JPanel"));

        frame.add(scroll, BorderLayout.CENTER);
        frame.add(panelbar, BorderLayout.SOUTH);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

定制类：

public class CustomBorder extends AbstractBorder {
    private static final long serialVersionUID = 1L;
    Insets i;

    CustomBorder() {
        i = new Insets(10, 20, 10, 20);
    }

    @Override
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
        super.paintBorder(c, g, x, y, width, height);

        Polygon bubble = new Polygon();
        bubble.addPoint(x + 10, y + 5);
        bubble.addPoint(x + width - 10, y + 5);
        bubble.addPoint(x + width - 10, y + height / 3);
        bubble.addPoint(x + width, y + height / 2);
        bubble.addPoint(x + width - 10, y + height * 2 / 3);
        bubble.addPoint(x + width - 10, y - 5 + height);
        bubble.addPoint(x + 10, y - 5 + height);

        Graphics2D g2d = (Graphics2D) g;
        Area rect = new Area(new Rectangle(x, y, width, height));
        rect.subtract(new Area(bubble));
        g2d.setClip(rect);
        g2d.setColor(c.getParent().getBackground());
        g2d.fillRect(0, 0, width, height);
        g2d.setClip(null);
        g2d.setColor(Color.BLACK);
        g2d.draw(bubble);
    }

    @Override
    public Insets getBorderInsets(Component c) {
        return i;
    }

    @Override
    public Insets getBorderInsets(Component c, Insets insets) {
        return i;
    }
}

裁剪代码有两个问题：

1. 减去气泡时，您没有从原始剪辑开始（导致组件被绘制在滚动窗格之外）
2. 在绘制气泡之前，您不会恢复原始剪辑：

变化将是：

@Override
public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
    super.paintBorder(c, g, x, y, width, height);

    Polygon bubble = new Polygon();
    bubble.addPoint(x + 10, y + 5);
    bubble.addPoint(x + width - 10, y + 5);
    bubble.addPoint(x + width - 10, y + height / 3);
    bubble.addPoint(x + width, y + height / 2);
    bubble.addPoint(x + width - 10, y + height * 2 / 3);
    bubble.addPoint(x + width - 10, y - 5 + height);
    bubble.addPoint(x + 10, y - 5 + height);

    Graphics2D g2d = (Graphics2D) g;
    //Area rect = new Area(new Rectangle(x, y, width, height));
    Shape clip = g2d.getClip();
    Area rect = new Area(clip);
    rect.subtract(new Area(bubble));
    g2d.setClip(rect);
    g2d.setColor(c.getParent().getBackground());
    g2d.fillRect(0, 0, width, height);
    //g2d.setClip(null);
    g2d.setClip(clip);
    g2d.setColor(Color.BLACK);
    g2d.draw(bubble);
}