我真的被困在如何进行编程上.如何在Java中绘制一个半径和边缘周围的圆?
I'm really stuck on how to go about programming this. How to draw a circle in Java with a radius and points around the edge?
我需要在 JFrame 内绘制一个圆,其半径和点围绕圆周.我可以数学计算如何找到边缘周围点的坐标,但我似乎无法对圆进行编程.我目前正在使用 Ellipse2D 方法,但这似乎不起作用并且不返回半径,据我了解,它不会从中心绘制圆,而是使用高度和宽度从起始坐标绘制圆.
I need to draw a circle within a JFrame with a radius and points around the circumference. i can mathematically calculate how to find the coordinates of the point around the edge but i cant seem to be able to program the circle. I am currently using a Ellipse2D method but that doesn't seem to work and doesn't return a radius, as under my understanding, it doesn't draw the circle from the center rather from a starting coordinate using a height and width.
我当前的代码在一个单独的框架上,但我需要将它添加到我现有的框架中.
My current code is on a separate frame but I need to add it to my existing frame.
import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;
public class circle extends JFrame {
public circle() {
super("circle");
setSize(410, 435);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Panel sp = new Panel();
Container content = getContentPane();
content.add(sp);
setContentPane(content);
setVisible(true);
}
public static void main (String args[]){
circle sign = new circle();
}
}
class Panel extends JPanel {
public void paintComponent(Graphics comp) {
super.paintComponent(comp);
Graphics2D comp2D = (Graphics2D) comp;
comp2D.setColor(Color.red);
Ellipse2D.Float sign1 = new Ellipse2D.Float(0F, 0F, 350F, 350F);
comp2D.fill(sign1);
}
}
circle 上的点 可以指定为角度 θ 的函数:
Points on a circle may be specified as a function of the angle θ:
x = a + r cos(θ)
y = b + r sin(θ)
这里显示了2π/8的增量.
附录:正如 @Christoffer Hammarström 的评论中所建议的,这个 修订 示例减少了 magic numbers 原文.所需的点数成为构造函数的参数.它还使渲染适应容器的大小.
Addendum: As suggested in a comment by @Christoffer Hammarström, this revised example reduces the number of magic numbers in the original. The desired number of points becomes a parameter to the constructor. It also adapts the rendering to the container's size.
/** @see https://stackoverflow.com/questions/2508704 */
public class CircleTest extends JPanel {
private static final int SIZE = 256;
private int a = SIZE / 2;
private int b = a;
private int r = 4 * SIZE / 5;
private int n;
/** @param n the desired number of circles. */
public CircleTest(int n) {
super(true);
this.setPreferredSize(new Dimension(SIZE, SIZE));
this.n = n;
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(Color.black);
a = getWidth() / 2;
b = getHeight() / 2;
int m = Math.min(a, b);
r = 4 * m / 5;
int r2 = Math.abs(m - r) / 2;
g2d.drawOval(a - r, b - r, 2 * r, 2 * r);
g2d.setColor(Color.blue);
for (int i = 0; i < n; i++) {
double t = 2 * Math.PI * i / n;
int x = (int) Math.round(a + r * Math.cos(t));
int y = (int) Math.round(b + r * Math.sin(t));
g2d.fillOval(x - r2, y - r2, 2 * r2, 2 * r2);
}
}
private static void create() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new CircleTest(9));
f.pack();
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
create();
}
});
}
}
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