java - 绕点 java 旋转三角形

Question

我遇到麻烦了。我需要使用拖动监听器和单击监听器围绕其中心旋转等边三角形。三角形应该变大，但现在会改变角度并旋转一个点，同时以三角形的中间为中心。这是我的问题，它当前正在拖动点 3 并围绕点 1 旋转。我有一个值 x 和 y 的数组，它存储 4 个值，每个值包含初始点第一个在序数值 0 和点 1 2 和 3 在相应的值。

`

public class DrawTriangle extends JFrame {

enter code here
/** The Constant NUMBER_3. */
private static final int NUMBER_3 = 3;

/** The Constant EQUL_ANGLE. */
@SuppressWarnings("unused")
private static final double EQUL_ANGLE = 1;

/** The Constant TRIANGLE_POINTS. */
private static final int TRIANGLE_POINTS = 4;

/** The Constant _400. */
private static final int SIZE = 400;

/** The x points. */
private int [] xPoints = new int[TRIANGLE_POINTS];

/** The y points. */
private int [] yPoints = new int[TRIANGLE_POINTS];

private int xInitial;

private int yInitial;

/** The x. */
private double x = EQUL_ANGLE;

/** The new x. */
private double newX;

/** The new y. */
private double newY;

/**
 * Instantiates a new draw triangle.
 */
public DrawTriangle() {
    super("Dimitry Rakhlei");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setContentPane(new DrawTrianglePanel());
    setSize(SIZE, SIZE); // you can change this size but don't make it HUGE!
    setVisible(true);
}

/**
 * The Class DrawTrianglePanel.
 */
private class DrawTrianglePanel extends JPanel implements MouseListener,
        MouseMotionListener {

    /**
     * Instantiates a new draw triangle panel.
     */
    public DrawTrianglePanel() {
        addMouseListener(this);
        addMouseMotionListener(this);
    }

    /**
     * Drawing the triangle.
     *
     * @param g
     *            the g
     * @see javax.swing.JComponent#paintComponent(java.awt.Graphics)
     */
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        // DRAWING CODE HERE
        g.drawPolygon(xPoints, yPoints, 3);
        System.out.println("Paint called");
    }



    /**
     * (non-Javadoc).
     *
     * @param e
     *            the e
     * @see java.awt.event.MouseListener#mousePressed
     * (java.awt.event.MouseEvent)
     */
    public void mousePressed(MouseEvent e) {
        System.out.println("Mouse pressed called");
        e.getPoint();
        xPoints[0] = e.getPoint().x;
        yPoints[0] = e.getPoint().y;
        repaint();

    }

    /**
     * (non-Javadoc).
     *
     * @param e
     *            the e
     * @see java.awt.event.MouseListener#mouseReleased
     * (java.awt.event.MouseEvent)
     */
    public void mouseReleased(MouseEvent e) {
        System.out.println("Mouse released called");
    }

    /**
     * (non-Javadoc).
     *
     * @param e
     *            the e
     * @see java.awt.event.MouseMotionListener#mouseDragged
     * (java.awt.event.MouseEvent)
     */
    public void mouseDragged(MouseEvent e) {
        System.out.println("Mouse dragged called");
        newX = e.getPoint().x;
        newY = e.getPoint().y;
        xPoints[1] = (int) newX;
        yPoints[1] = (int) newY;


        newX = xPoints[0] + (xPoints[1]-xPoints[0])*Math.cos(x) - (yPoints[1]-yPoints[0])*Math.sin(x);

        newY = yPoints[0] + (xPoints[1]-xPoints[0])*Math.sin(x) + (yPoints[1]-yPoints[0])*Math.cos(x);

        xPoints[2] = (int) newX;
        yPoints[2] = (int) newY;

        newX = xPoints[0] + (xPoints[1]-xPoints[0])*Math.cos(x) - (yPoints[1]-yPoints[0])*Math.sin(x);

        newY = yPoints[0] + (xPoints[1]-xPoints[0])*Math.sin(x) + (yPoints[1]-yPoints[0])*Math.cos(x);

        xPoints[3] = (int) newX;
        yPoints[3] = (int) newY;

        repaint();
    }

    /**
     * (non-Javadoc).
     *
     * @param e
     *            the e
     * @see java.awt.event.MouseListener#mouseEntered
     * (java.awt.event.MouseEvent)
     */
    public void mouseEntered(MouseEvent e) {
        System.out.println("Mouse Entered.");
    }

    /**
     * (non-Javadoc).
     *
     * @param e
     *            the e
     * @see java.awt.event.MouseListener#mouseExited
     * (java.awt.event.MouseEvent)
     */
    public void mouseExited(MouseEvent e) {
        System.out.println("Mouse exited.");
    }

    /**
     * (non-Javadoc).
     *
     * @param e
     *            the e
     * @see java.awt.event.MouseListener#mouseClicked
     * (java.awt.event.MouseEvent)
     */
    public void mouseClicked(MouseEvent e) {
    }

    /**
     * (non-Javadoc).
     *
     * @param e
     *            the e
     * @see java.awt.event.MouseMotionListener#mouseMoved
     * (java.awt.event.MouseEvent)
     */
    public void mouseMoved(MouseEvent e) {
    }

}

/**
 * The main method.
 *
 * @param args
 *            the arguments
 */
public static void main(String[] args) {
    new DrawTriangle();
}

};` 

我的问题是这段代码基本上运行正确，但我被告知旋转的顶点必须位于三角形的中间。我的就是第一点。

Answer 1

首先查看 2D Graphics ，特别是Transforming Shapes, Text, and Images .

基本上，你的“多边形”将有一个可定义的尺寸(最大x/y点)，由此，你可以确定“多边形”的中心位置，例如......

protected Dimension getTriangleSize() {
    int maxX = 0;
    int maxY = 0;
    for (int index = 0; index < xPoints.length; index++) {
        maxX = Math.max(maxX, xPoints[index]);
    }
    for (int index = 0; index < yPoints.length; index++) {
        maxY = Math.max(maxY, yPoints[index]);
    }
    return new Dimension(maxX, maxY);
}

这仅返回多边形的最大 x 和 y 边界。这允许您计算多边形的中心位置。您很快就会明白为什么不需要实际指定原点...

接下来，我们计算一个AffineTransform，它直接应用于Graphics上下文...

Graphics2D g2d = (Graphics2D) g.create();
AffineTransform at = new AffineTransform();
Dimension size = getTriangleSize();
int x = clickPoint.x - (size.width / 2);
int y = clickPoint.y - (size.height / 2);
at.translate(x, y);
at.rotate(Math.toRadians(angle), clickPoint.x - x, clickPoint.y - y);
g2d.setTransform(at);
g2d.drawPolygon(xPoints, yPoints, 3);
// Guide
g2d.setColor(Color.RED);
g2d.drawLine(size.width / 2, 0, size.width / 2, size.height / 2);
g2d.dispose();

这不仅会平移三角形位置，还会旋转它。这意味着您可以创建一个标准化的多边形(其原点是 0x0)并允许图形上下文将其放置在您想要的位置，这使生活变得更加轻松...

现在，旋转计算是基于计算两点之间的角度，即“单击”点和“拖动”点...

angle = -Math.toDegrees(Math.atan2(e.getPoint().x - clickPoint.x, e.getPoint().y - clickPoint.y)) + 180;

这是基于this question中的解决方案

例如...

红线是简单的指导，表明三角形的尖端指向鼠标...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.AffineTransform;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class DrawTriangle extends JFrame {

    /**
     * The x points.
     */
    private int[] xPoints = new int[]{0, 25, 50};

    /**
     * The y points.
     */
    private int[] yPoints = new int[]{50, 0, 50};

    double angle = 0f;

    /**
     * Instantiates a new draw triangle.
     */
    public DrawTriangle() {
        super("Dimitry Rakhlei");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setContentPane(new DrawTrianglePanel());
        pack();
        setLocationRelativeTo(null);
        setVisible(true);
    }

    /**
     * The Class DrawTrianglePanel.
     */
    private class DrawTrianglePanel extends JPanel implements MouseListener,
                    MouseMotionListener {

        private Point clickPoint;

        /**
         * Instantiates a new draw triangle panel.
         */
        public DrawTrianglePanel() {
            addMouseListener(this);
            addMouseMotionListener(this);
            clickPoint = new Point(100, 100);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected Dimension getTriangleSize() {

            int maxX = 0;
            int maxY = 0;
            for (int index = 0; index < xPoints.length; index++) {
                maxX = Math.max(maxX, xPoints[index]);
            }
            for (int index = 0; index < yPoints.length; index++) {
                maxY = Math.max(maxY, yPoints[index]);
            }
            return new Dimension(maxX, maxY);
        }

        /**
         * Drawing the triangle.
         *
         * @param g the g
         * @see javax.swing.JComponent#paintComponent(java.awt.Graphics)
         */
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            Graphics2D g2d = (Graphics2D) g.create();
            AffineTransform at = new AffineTransform();
            Dimension size = getTriangleSize();
            int x = clickPoint.x - (size.width / 2);
            int y = clickPoint.y - (size.height / 2);
            at.translate(x, y);
            at.rotate(Math.toRadians(angle), clickPoint.x - x, clickPoint.y - y);
            g2d.setTransform(at);
            g2d.drawPolygon(xPoints, yPoints, 3);
            // Guide
            g2d.setColor(Color.RED);
            g2d.drawLine(size.width / 2, 0, size.width / 2, size.height / 2);
            g2d.dispose();

        }

        /**
         * (non-Javadoc).
         *
         * @param e the e
         * @see java.awt.event.MouseListener#mousePressed (java.awt.event.MouseEvent)
         */
        @Override
        public void mousePressed(MouseEvent e) {
            System.out.println("Mouse pressed called");
            //          clickPoint = e.getPoint();
            repaint();

        }

        /**
         * (non-Javadoc).
         *
         * @param e the e
         * @see java.awt.event.MouseListener#mouseReleased (java.awt.event.MouseEvent)
         */
        @Override
        public void mouseReleased(MouseEvent e) {
            System.out.println("Mouse released called");
        }

        /**
         * (non-Javadoc).
         *
         * @param e the e
         * @see java.awt.event.MouseMotionListener#mouseDragged (java.awt.event.MouseEvent)
         */
        public void mouseDragged(MouseEvent e) {
            System.out.println("Mouse dragged called");

            angle = -Math.toDegrees(Math.atan2(e.getPoint().x - clickPoint.x, e.getPoint().y - clickPoint.y)) + 180;

            repaint();
        }

        /**
         * (non-Javadoc).
         *
         * @param e the e
         * @see java.awt.event.MouseListener#mouseEntered (java.awt.event.MouseEvent)
         */
        public void mouseEntered(MouseEvent e) {
            System.out.println("Mouse Entered.");
        }

        /**
         * (non-Javadoc).
         *
         * @param e the e
         * @see java.awt.event.MouseListener#mouseExited (java.awt.event.MouseEvent)
         */
        public void mouseExited(MouseEvent e) {
            System.out.println("Mouse exited.");
        }

        /**
         * (non-Javadoc).
         *
         * @param e the e
         * @see java.awt.event.MouseListener#mouseClicked (java.awt.event.MouseEvent)
         */
        public void mouseClicked(MouseEvent e) {
        }

        /**
         * (non-Javadoc).
         *
         * @param e the e
         * @see java.awt.event.MouseMotionListener#mouseMoved (java.awt.event.MouseEvent)
         */
        public void mouseMoved(MouseEvent e) {
        }

    }

    /**
     * The main method.
     *
     * @param args the arguments
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                new DrawTriangle();
            }
        });
    }

}

现在，在你对我大发雷霆并提示解决方案“太复杂”之前，请理解我是个白痴，说真的，我 2 岁的 child 对基础数学的掌握比我更好，这就是我能想出的最简单的解决方案不会融化我的大脑并使用双数组多边形 API。就我个人而言，我会使用 Shape API，但这不是您开始使用的...