java - 无法使用 .transform 更改 Path2D.Double

Question

我的程序应该允许用户将矩阵的前六个数字输入到文本字段中，然后单击“应用”按钮，使用 .transform 方法更改 Path2D，参数是输入的六个数字。我的问题是，每当我输入内容并点击“应用”时，转换与应有的效果截然不同，并且原始箭头也保留在后面。

这真的很奇怪，我不知道问题出在哪里。仿射变换的一切都应该在正确的位置，但变换结果却完全错误。

它应该是这样的:

这对我来说是这样的:

我将把完整的代码放在下面，这样你就可以自己运行它，看看你是否能够弄清楚。谢谢!

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.geom.GeneralPath;
import java.awt.geom.Path2D;
import javax.swing.event.*;

public class Project3 extends JPanel implements ActionListener {

    public static Project3 p = new Project3();
    Path2D.Double arrow = new Path2D.Double();
    public static JTextField
            num1 = new JTextField("1"), num2 = new JTextField("0"),
            num3 = new JTextField("0"), num4 = new JTextField("0"),
            num5 = new JTextField("1"), num6 = new JTextField("0");

    public Project3() {
        setBackground(Color.WHITE);
    }

    public Path2D.Double drawArrow() {
        arrow.setWindingRule(GeneralPath.WIND_EVEN_ODD);
        arrow.moveTo(0, 0);
        arrow.lineTo(0, -100); 
        arrow.moveTo(0, -200);
        arrow.lineTo(100, -100);
        arrow.lineTo(50, -100);
        arrow.lineTo(50, 100);
        arrow.quadTo(0, 0, -50, 100);
        arrow.lineTo(-50, -100);
        arrow.lineTo(-100, -100);
        arrow.lineTo(0, -200);
        arrow.closePath();
        return arrow;
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.translate(250, 250);
        GradientPaint gradient = new GradientPaint(0, 0, Color.LIGHT_GRAY, 15, 15, Color.BLACK, true);
        g2.setPaint(gradient);
        g2.setStroke(new BasicStroke(12, BasicStroke.CAP_ROUND, BasicStroke.JOIN_MITER));
        g2.draw(drawArrow());
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Project 3");
        frame.setSize(500, 600);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container cp = frame.getContentPane();
        cp.setLayout(new BorderLayout());

        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        cp.add(panel, BorderLayout.CENTER);
        panel.add(p, BorderLayout.CENTER);
        panel = new JPanel();
        panel.setLayout(new GridLayout(0, 2));
        cp.add(panel, BorderLayout.SOUTH);

        JPanel textPanel = new JPanel();
        textPanel.setLayout(new GridLayout(2, 3));
        panel.add(textPanel);
        textPanel.add(num1);
        textPanel.add(num2);
        textPanel.add(num3);
        textPanel.add(num4);
        textPanel.add(num5);
        textPanel.add(num6);

        JPanel btPanel = new JPanel();
        btPanel.setLayout(new GridLayout(0, 1));
        panel.add(btPanel);
        JButton apply = new JButton("Apply");
        apply.addActionListener(p);
        btPanel.add(apply);
        JButton reset = new JButton("Reset");
        reset.addActionListener(p);
        btPanel.add(reset);

        frame.setVisible(true);

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        switch (command) {
            case "Apply":
                double args1 = Double.parseDouble(num1.getText());
                double args2 = Double.parseDouble(num2.getText());
                double args3 = Double.parseDouble(num3.getText());
                double args4 = Double.parseDouble(num4.getText());
                double args5 = Double.parseDouble(num5.getText());
                double args6 = Double.parseDouble(num6.getText());          
                arrow.transform(new AffineTransform(args1, args2, args3, args4, args5, args6));
                repaint();
                break;
            case "Reset":
                arrow.transform(new AffineTransform(1, 0, 0, 0, 1, 0));
                repaint();
                break;
        }
    }

}

Answer 1

您的部分问题似乎是 AffineTransform 参数的顺序。您可能假设您的 JTextField 与 2x3 矩阵的形式相同，但事实并非如此。向 JTextField 添加边框即可明白我的意思:

    num00.setBorder(BorderFactory.createTitledBorder("m00"));
    num10.setBorder(BorderFactory.createTitledBorder("m10"));
    num01.setBorder(BorderFactory.createTitledBorder("m01"));
    num11.setBorder(BorderFactory.createTitledBorder("m11"));
    num02.setBorder(BorderFactory.createTitledBorder("m02"));
    num12.setBorder(BorderFactory.createTitledBorder("m12"));

和:

        double m00 = Double.parseDouble(num00.getText());
        double m10 = Double.parseDouble(num10.getText());
        double m01 = Double.parseDouble(num01.getText());
        double m11 = Double.parseDouble(num11.getText());
        double m02 = Double.parseDouble(num02.getText());
        double m12 = Double.parseDouble(num12.getText());
        AffineTransform transform = new AffineTransform(m00, m10, m01, m11,
                m02, m12); 

你会发现事情并不按照你假设的顺序进行。相反，添加您的 JTextfields，以便它们匹配矩阵顺序:

    textPanel.add(num00);
    textPanel.add(num10);
    textPanel.add(num02);
    textPanel.add(num01);
    textPanel.add(num11);
    textPanel.add(num12);

这将改善您的发现。

类似于:

import javax.swing.*;

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.geom.GeneralPath;
import java.awt.geom.NoninvertibleTransformException;
import java.awt.geom.Path2D;
import java.util.Deque;
import java.util.LinkedList;

import javax.swing.event.*;

public class Project3 extends JPanel implements ActionListener {

    public static Project3 p = new Project3();
    Path2D arrow; // !!
    public static
    JTextField 
    num00 = new JTextField("0"), 
    num10 = new JTextField("1"), 
    num01 = new JTextField("1"), 
    num11 = new JTextField("0"),            
    num02 = new JTextField("0"), 
    num12 = new JTextField("0");
    private static Deque<AffineTransform> atStack = new LinkedList<>(); 

    public Project3() {
        setBackground(Color.WHITE);
        arrow = drawArrow(); // !! create the arrow only once
    }

    public Path2D drawArrow() { // !!
        arrow = new Path2D.Double(); // !!
        arrow.setWindingRule(GeneralPath.WIND_EVEN_ODD);
        arrow.moveTo(0, 0);
        arrow.lineTo(0, -100);
        arrow.moveTo(0, -200);
        arrow.lineTo(100, -100);
        arrow.lineTo(50, -100);
        arrow.lineTo(50, 100);
        arrow.quadTo(0, 0, -50, 100);
        arrow.lineTo(-50, -100);
        arrow.lineTo(-100, -100);
        arrow.lineTo(0, -200);
        arrow.closePath();
        arrow.transform(AffineTransform.getTranslateInstance(250, 250)); // !! shift it here
        return arrow;
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON); // !!
        // !! g2.translate(250, 250);  // translate the arrow, not Graphics
        GradientPaint gradient = new GradientPaint(0, 0, Color.LIGHT_GRAY, 15,
                15, Color.BLACK, true);
        g2.setPaint(gradient);
        g2.setStroke(new BasicStroke(12, BasicStroke.CAP_ROUND,
                BasicStroke.JOIN_MITER));
        // g2.draw(drawArrow()); // !!  don't re-create the arrow
        g2.draw(arrow);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Project 3");
        frame.setSize(500, 600);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container cp = frame.getContentPane();
        cp.setLayout(new BorderLayout());

        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        cp.add(panel, BorderLayout.CENTER);
        panel.add(p, BorderLayout.CENTER);
        panel = new JPanel();
        panel.setLayout(new GridLayout(0, 2));
        cp.add(panel, BorderLayout.SOUTH);

        JPanel textPanel = new JPanel();
        textPanel.setLayout(new GridLayout(2, 3));
        panel.add(textPanel);
        num00.setBorder(BorderFactory.createTitledBorder("m00"));
        num10.setBorder(BorderFactory.createTitledBorder("m10"));
        num01.setBorder(BorderFactory.createTitledBorder("m01"));
        num11.setBorder(BorderFactory.createTitledBorder("m11"));
        num02.setBorder(BorderFactory.createTitledBorder("m02"));
        num12.setBorder(BorderFactory.createTitledBorder("m12"));

        textPanel.add(num00);
        textPanel.add(num10);
        textPanel.add(num02);
        textPanel.add(num01);
        textPanel.add(num11);
        textPanel.add(num12);

        JPanel btPanel = new JPanel();
        btPanel.setLayout(new GridLayout(0, 1));
        panel.add(btPanel);
        JButton apply = new JButton("Apply");
        apply.addActionListener(p);
        btPanel.add(apply);
        JButton reset = new JButton("Reset");
        reset.addActionListener(p);
        btPanel.add(reset);

        frame.setVisible(true);

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String command = e.getActionCommand();
        switch (command) {
        case "Apply":
            double m00 = Double.parseDouble(num00.getText());
            double m10 = Double.parseDouble(num10.getText());
            double m01 = Double.parseDouble(num01.getText());
            double m11 = Double.parseDouble(num11.getText());
            double m02 = Double.parseDouble(num02.getText());
            double m12 = Double.parseDouble(num12.getText());
            AffineTransform transform = new AffineTransform(m00, m10, m01, m11,
                    m02, m12); 
            arrow.transform(transform);
            atStack.addFirst(transform); // save the transform
            repaint();
            break;
        case "Reset":
            // !! arrow.transform(new AffineTransform(1, 0, 0, 0, 1, 0));
            while (atStack.size() > 0) {
                AffineTransform at = atStack.removeFirst();

                // inverse fails if determinant is 0
                if (at.getDeterminant() == 0) {
                    return;
                }
                try {
                    arrow.transform(at.createInverse());
                } catch (NoninvertibleTransformException e1) {
                    e1.printStackTrace();
                }
            }
            repaint();
            break;
        }
    }

}

我还使用队列作为堆栈来保存已应用的变换，以允许它们在重置时按顺序取消完成。