我遇到了麻烦.我需要使用拖动侦听器和单击侦听器围绕其中心旋转等边三角形.三角形应该会增长，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，它目前正在拖动点 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，每个值首先在序数值 0 处包含初始点，在点 1 2 和 3 处对应的值.
I am having trouble. I need to rotate an equilateral triangle around it's centre by using the drag listener and click listener. The triangle should grow but now change angles and be rotated by a point while being centred at the middle of the triangle. This is my problem, it is currently dragging by the point 3 and rotating around point 1. I have an array of values x and y and it stores 4 values each containing the initial point first at ordinal value 0 and point 1 2 and 3 at the corresponding values.
`
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在三角形的中间.我的是第一点.
My issue is that this code basically runs correctly but I am told the vertex point of rotation has to be in the middle of the triangle. Mine is the first point.
先看看 2D 图形，特别是 变换形状、文本、和图片.
基本上，您的多边形"将具有可定义的大小(最大 x/y 点)，由此，您可以确定多边形"的中心位置，例如...
Basically, your "polygon" will have a definable size (the maximum x/y point), from this, you can determine the center position of the "polygon", for example...
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);
}
这只是返回多边形的最大 x 和 y 边界.这允许您计算多边形的中心位置.您马上就会明白为什么您不需要实际指定原点...
This just returns the maximum x and y bounds of your polygon. This allows you to calculate the center position of the polygon. You'll see why in a second why you don't need to actually specify the origin point...
接下来，我们计算一个AffineTransform，就是直接应用到Graphics上下文...
Next, we calculate a AffineTransform, which is the applied to the Graphics context directly...
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多边形(其原点为 0x0)并允许 Graphics 上下文将其放置在您想要的位置，这让生活变得更加轻松......
This not only translates the triangle position, but will also rotate it. What this means you can create a normalised polygon (whose origin point is 0x0) and allow the Graphics context to place it where you want it, this makes life SO much easier...
现在，旋转计算是基于计算两点之间的角度，点击"点和拖动"点...
Now, the rotation calculation is based on calculating the angle between two points, the "click" point and the "drag" point...
angle = -Math.toDegrees(Math.atan2(e.getPoint().x - clickPoint.x, e.getPoint().y - clickPoint.y)) + 180;
这基于 this question
例如...
红线是一个简单的指南，表明三角形的尖端指向鼠标...
The red line is simple a guide to show that the tip of the triangle is point towards the mouse...
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，在你跳到我头上抱怨解决方案太复杂"之前，请理解我是个白痴，说真的，我 2 岁的孩子对基础数学的掌握比我还好，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阵列多边形 API.就个人而言，我会使用 Shape API，但这不是你开始使用的......
Now, before you jump all over me and complain that the solution is "too complex", understand that I'm an idiot, seriously, my 2 year old has a better grasp on basic mathematics then I do, this is the most simplistic solution I can come up with that doesn't melt my brain and uses the dual array polygon API. Personally, I'd use the Shape API, but that's not what you started with...
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