paintComponent（）正在绘制其他组件 [英] paintComponent() is drawing on other components

问题描述

我正在使用自定义类，根据此答案中的代码，绘制一个形状像会话框。每当我调整应用程序窗口的大小足以使组件在顶部或底部突出时，所述组件的轮廓将在 JScrollPane 之外的其他组件之外绘制;在这种情况下 JPanel 。

I'm using a custom class, based on the code in this answer, to draw a background shaped like a speech bubble. Whenever I resize the window of my application enough to make a component poke out at the top or bottom, the outlines of the said component is drawn outside the JScrollPane on top of other components; in this case the JPanel.

在左侧图像中，组件底部的边框由于组件仍然可见，因此绘制了 JScrollPane ;而在右侧图像中，所提到的组件不再可见，一切看起来都是预期的。

In the left-side image, the border of the component at the bottom of the JScrollPane is drawn, due to the component still being visible; while in the right-side image, the mentioned component is no longer visible and everything looks as intended.

我认为这与我是这样的事实有关使用 JScrollPane 来包含组件，从而允许组件在 JPanel 下滑动。我如何防止这种情况？

I believe it has something to do with the fact that I'm using a JScrollPane to contain the components and thus allowing the component to slide under the JPanel. How do I prevent this?

< img src =https://i.stack.imgur.com/0TMen.pngalt =图片>

主要：

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);
    }
}

自定义类：

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;
    }
}

推荐答案

那里剪辑代码有两个问题：

There are two problems with the clipping code:

1. 在减去气泡时，你不会从原始剪辑开始（导致组件成为在滚动窗格外绘制）


2. 在绘制气泡之前，您不会恢复原始剪辑：

更改将是：

@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);
}

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