java - intersectsLine() 函数未按预期工作

Question

我正在尝试检查一条线是否与一组矩形相交。

这是我的代码:

public class Test {

    public static void main(String args[]) {
        Rectangle2D.Double rectangle1 = new Rectangle2D.Double(32, 64, 32, 32);     
        Rectangle2D.Double rectangle2 = new Rectangle2D.Double(0, 32, 32, 32);      

        Line2D.Double line = new Line2D.Double(36, 63, 5, 12);

        System.out.println(rectangle1.intersectsLine(line)); // outputs false. Why?
        System.out.println(rectangle2.intersectsLine(line)); // outputs true as expected
    }
}

正如您所看到的，起点 (36, 63) 在 rectangle1 内，但显然该线段并未与它开始的矩形相交。

但是，它与存储终点 (5, 12) 的矩形相交。

知道为什么吗？

如何让它检测交叉点？

Answer 1

该线不与矩形1 相交，这就是Java 给您返回正确答案的原因。在 GUI 中画出线条并亲自查看。也许您对 Rectangle2D.Double 构造函数感到困惑 - 最后一个参数是宽度和高度。

绘制 GUI 并查看；他们几乎接触，但又不完全接触:

绘制两个矩形:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.*;

import javax.swing.*;

public class Test extends JPanel {
    private static final int PREF_W = 850;
    private static final int PREF_H = PREF_W;
    Rectangle2D rectangle1 = new Rectangle2D.Double(32, 64, 32, 32);     
    // Rectangle2D rectangle2 = new Rectangle2D.Double(0, 32, 32, 32);      

    Line2D line = new Line2D.Double(36, 63, 5, 12);

    public Test() {
        // TODO Auto-generated constructor stub
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        double scale = 8.0;
        g2.scale(scale, scale); // make it big to show it for you
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2.draw(rectangle1);
        // g2.draw(rectangle2);
        g2.draw(line);
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    private static void createAndShowGui() {
        Test mainPanel = new Test();

        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGui();
            }
        });
    }
}