Java awt 围绕一个圆圈绘制元素

Question

我正在写一个小游戏，遇到了一个问题。我需要在一个大圆的边界处画 64 个小圆。所以我想要这样的东西：

我已经尝试了很多东西，但都没有用。如何在 java 中使用 java.awt.Component#paint() 方法和 java.awt.Graphics class?

完成此操作

谢谢。

Answer 1

因此，您的基本问题归结为“根据给定角度在圆上找到一个点”

快速 google 会找到像 Find the coordinates of a point on a circle, now, to be frank, I'm an idiot, so I'd narrow my search to include Java, which would give us something like - sweet.

这样的资源

所以基本计算可能类似于

double xPosy = Math.cos(rads) * radius);
double yPosy = Math.sin(rads) * radius);

现在，这解决了您问题的核心方面。剩下的就是简单地绘制结果。有关 API.

的更详细信息，请参阅 Performing Custom Painting and Painting in AWT and Swing as a starting point and 2D Graphics

现在，考虑到以上所有内容，您最终可能会得到一个类似于...

的解决方案

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
        }

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

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            int midX = getWidth() / 2;
            int midY = getHeight() / 2;
            Dimension size = new Dimension(4, 4);
            g2d.setColor(Color.BLACK);
            for (int index = 0; index < 64; index++) {
                double angle = (360d / 64d) * index;
                Point2D poc = getPointOnCircle(angle, 100 - 4);
                Rectangle2D box = new Rectangle2D.Double(midX + poc.getX() - 2, midY + poc.getY() - 2, size.width, size.height);
                g2d.draw(box);
            }
            g2d.dispose();
        }

        protected Point2D getPointOnCircle(double degress, double radius) {
            double rads = Math.toRadians(degress - 90); // 0 becomes the top

            return new Point2D.Double(Math.cos(rads) * radius, Math.sin(rads) * radius);
        }
    }
}

所以，大约现在，您应该意识到我的“正方形”是正方形，而不是像您的“菱形”形状。这是您必须开始做一些工作的地方。

如果我正在处理这个问题，我可能会想创建一个自定义形状，或者对 box 应用 45 度变换并平移它的位置以渲染它，或者只是将整个结果旋转45 度，但这会带来一大堆其他问题，具体取决于您要用它做什么

Answer 2

这是一种方法（其中大部分是用于设置包含框架和面板的样板）。它使用 sine and cosine 方法计算 unit 圆的点。然后通过首先乘以所需较大圆的 radius 然后通过添加 center x,y 偏移量将其置于面板中心来调整这些点。

它包含的唯一真正特别的东西是

保证外圆之间的距离为其直径之一。因此，如果圆圈数量减少，则尺寸会增加。这可以根据您的需要进行调整。
我使用 RenderingHints 在视觉上平滑了曲线。最后
我添加了一个具有任意限制的简单 WheelListener，这样您可以在上下移动鼠标滚轮时看到变化。这会修改 NCIRCLES（不应该用常量做的事情）然后重新绘制面板。它很容易删除。

public class CircleBorder extends JPanel {

    JFrame frame = new JFrame("Circle Border");
    static int BIG_RADIUS = 200;
    static int NCIRCLES = 60;
    static int WIDTH = 500;
    static int HEIGHT = 500;

    public static void main(String[] args ) {
        SwingUtilities.invokeLater(()->new CircleBorder().start());
    }
    public void start() {
     addMouseWheelListener((we)-> {
           int rot = we.getWheelRotation();
           if (NCIRCLES < 70 && rot > 0 || NCIRCLES > 7 && rot < 0) {
               NCIRCLES += rot;
           }
              
           repaint();
       });
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       frame.add(this);
       frame.pack();
       // center on screen
       frame.setLocationRelativeTo(null);
       frame.setVisible(true);
    }
    @Override
    public Dimension getPreferredSize() {
        return new Dimension(WIDTH,HEIGHT);
    }
    
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g.create();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        
        int centerX = WIDTH/2;
        int centerY = HEIGHT/2;
        
        double angleIncrement = 2*Math.PI/NCIRCLES;
        g2d.setColor(Color.RED);
        
        // the next two lines adjusts the little radius so that each
        // outer circle will be one diameter apart.

        int bigD = (int)(Math.PI*2*BIG_RADIUS);
        int littleRadius = bigD/(NCIRCLES*4);
        
        // Compute the x and y coordinates of the center of the outer
        // circles. Then iterate once around the circle based on the
        // computed angle above to draw the circumference. The little
        // radius is subtracted to ensure those circles are
        // centered on the large circles circumference.

        double angle = 0;
        for (int i = 0; i < NCIRCLES; i++) {
              int x = (int)(centerX + Math.cos(angle)*BIG_RADIUS) 
                                    - littleRadius;
              int y = (int)(centerY + Math.sin(angle)*BIG_RADIUS) 
                                    - littleRadius;
              g2d.fillOval(x,y,littleRadius*2,littleRadius*2);
              angle += angleIncrement;
        }
        
        g2d.dispose();
    }
}

Answer 3

感谢@MadProgrammer 的回答。我将他的代码与@WJS 提出的使用 RenderingHints 的建议和我自己的想法结合起来，下面的代码对我有用。

package gui;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Point2D;

import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.WindowConstants;

/**
 * Thanks to <a
 * href=https://whosebug.com/users/992484/madprogrammer>@MadProgrammer</a>
 * on Whosebug for the geometry part (<a
 * href=
 * code</a>)
 */
public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setExtendedState(Frame.MAXIMIZED_BOTH);
                frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JComponent {

        public TestPane() {
        }

        @Override
        public Dimension getPreferredSize() {
            return getParent().getSize();
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            Graphics2D g2d = (Graphics2D) g.create();
            //Thanks to @WJS for the idea
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            int midX = getWidth() / 2;
            int midY = getHeight() / 2;
            int min = Math.min(getHeight() / 2, getWidth() / 2);
            Dimension size = new Dimension(min / 20, min / 20);
            double minsize = Math.min(size.getHeight(), size.getWidth());
            double radius = min - minsize;

            g2d.setColor(Color.BLACK);
            for (int index = 0; index < 64; index++) {
                double angle = (360d / 64d) * index;
                double rads = Math.toRadians(angle - 90); // 0 becomes the top
                Point2D poc = new Point2D.Double(Math.cos(rads) * radius, Math.sin(rads) * radius);
                g2d.fillOval((int) (midX + poc.getX() - 2), (int) (midY + poc.getY() - 2), size.width, size.height);
            }
            g2d.dispose();
        }
    }
}

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