使用Java的Path2D创建钢笔工具时遇到的问题

Question

我一直在尝试使用Path2D类和鼠标侦听器为Java绘图程序创建钢笔工具，但结果令人困惑。该工具将工作几秒钟，但随后整个应用程序将冻结，必须关闭。（这里没有例外；程序只会冻结）。这是一个说明问题的SSCCE：

import java.awt.BasicStroke;
import java.awt.event.MouseAdapter;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Shape;
import java.awt.event.MouseEvent;
import java.awt.geom.Path2D;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class PenDemoPanel extends JPanel {

    private Point start;
    private Point stop;
    private Shape shape;

    public PenDemoPanel() {
        setBackground(Color.white);
        setPreferredSize(new Dimension(600, 600));
        PathListener listener = new PathListener();
        addMouseListener(listener);
        addMouseMotionListener(listener);
    }

    public void paintComponent(Graphics gc) {
        super.paintComponent(gc);

        Graphics2D g2 = (Graphics2D) gc;

        if (start != null && stop != null) {
            BasicStroke stroke = new BasicStroke(1);
            shape = stroke.createStrokedShape(shape);
            g2.draw(shape);
            g2.fill(shape);
        }

    }

    private class PathListener
        extends MouseAdapter {

        public void mousePressed(MouseEvent event) {
            start = event.getPoint();
            Path2D path = new Path2D.Double();
            shape = path;
        }

        public void mouseDragged(MouseEvent event) {
            stop = event.getPoint();

            Path2D path = (Path2D) shape;
            path.moveTo(start.x, start.y);
            path.lineTo(stop.x, stop.y);
            shape = path;
            start = stop;

            repaint();

        }

        public void mouseReleased(MouseEvent event) {
            Path2D path = (Path2D) shape;
            path.closePath();
            shape = path;
            repaint();
        }
    }

    public static void main(String[] args) {
        PenDemoPanel shapes = new PenDemoPanel();

        JFrame frame = new JFrame("PenDemo");

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(shapes);

        frame.pack();
        frame.setVisible(true);
    }
}

我编写了自己的Path类，在这里可以很好地工作，但是我想在Path2D类中使用一些其他功能。

我在这里做错什么了吗？还是Path2D无法执行我想做的事情？

任何帮助将不胜感激。

Answer 1

问题似乎出在将笔划形状分配回形状上。如果您避免这样做，请使用该应用程序。保持响应。可见

import java.awt.BasicStroke;
import java.awt.event.MouseAdapter;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Shape;
import java.awt.event.MouseEvent;
import java.awt.geom.Path2D;
import javax.swing.*;

public class PenDemoPanel extends JPanel {

    private Point start;
    private Point stop;
    private Shape shape;

    public PenDemoPanel() {
        setBackground(Color.white);
        setPreferredSize(new Dimension(600, 600));
        PathListener listener = new PathListener();
        addMouseListener(listener);
        addMouseMotionListener(listener);
    }

    public void paintComponent(Graphics gc) {
        super.paintComponent(gc);

        Graphics2D g2 = (Graphics2D) gc;

        if (start != null && stop != null) {
            BasicStroke stroke = new BasicStroke(1);
            Shape strokedShape = stroke.createStrokedShape(shape);
            g2.draw(strokedShape);
            g2.fill(strokedShape);
        }
    }

    private class PathListener
        extends MouseAdapter {

        public void mousePressed(MouseEvent event) {
            start = event.getPoint();
            Path2D path = new Path2D.Double();
            shape = path;
        }

        public void mouseDragged(MouseEvent event) {
            stop = event.getPoint();

            Path2D path = (Path2D) shape;
            path.moveTo(start.x, start.y);
            path.lineTo(stop.x, stop.y);
            shape = path;
            start = stop;

            repaint();
        }

        public void mouseReleased(MouseEvent event) {
            Path2D path = (Path2D) shape;
            try {
                path.closePath();
            } catch(Exception ingore) {
            }
            shape = path;
            repaint();
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                PenDemoPanel shapes = new PenDemoPanel();

                JFrame frame = new JFrame("PenDemo");

                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.getContentPane().add(shapes);

                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}