問題描述

我正在開發一個程序，我想在其中畫一條從圓心到其參數點的線.但它在圓周外和內圓周上畫線.我想根據 X 和 Y 角度在圓周上精確地畫線.

圓中心點:

x = 200y = 100半徑= 100

public SecondActivity(String azim,String ele) {初始化();設置標題(我的窗口")；`angle_x = Integer.parseInt(azim);angle_y = Integer.parseInt(ele);x = 200+r*Math.cos(angle_x);y = 100+r*Math.sin(angle_y);}公共無效油漆(圖形g){super.paint(g);drawCircle(g,200,100,r);畫線(g)；}公共無效drawCircle(圖形g，int x，int y，int r){g.setColor(Color.BLACK);g.drawOval(x, y, r*2,r*2);}公共無效drawLine(圖形g){Graphics2D g2d = (Graphics2D) g;g2d.setColor(Color.BLUE);g2d.draw(new Line2D.Double(300.0d,200.0d,x,y));}

您的代碼(和邏輯)中有幾個錯誤:

1. 您使用 2 個角度來計算 X 和 Y 坐標，因此會得到奇怪的結果.根據這個

2. 您使用的角度是度數，但 Math.cos(angle) 和 Math.sin(angle) 要求 angle 以弧度表示，因此，您必須將角度轉換為弧度，如 Math.roRadians(angle)，如以下問題所示:

   I am working on a program in which I want to draw a line from circle's center to its parametric point. But it draws line out of circumference and inside circumference. I want to draw line exactly on circumference according to X and Y angles.

   Circle center points:

   x = 200
   y = 100
   radius= 100
   

   public SecondActivity(String azim,String ele) {
       initialize();
       setTitle("My WIndow");`
   
       angle_x = Integer.parseInt(azim);
       angle_y = Integer.parseInt(ele);
   
       x = 200+r*Math.cos(angle_x);
       y = 100+r*Math.sin(angle_y);      
   }
   
   public void paint(Graphics g) {
       super.paint(g);
   
       drawCircle(g,200,100,r);
       drawLine(g);
   }
   
   public void drawCircle(Graphics g,int x,int y,int r) {
       g.setColor(Color.BLACK);
       g.drawOval(x, y, r*2,r*2);
   }
   public void drawLine(Graphics g) {
       Graphics2D g2d = (Graphics2D) g;    
       g2d.setColor(Color.BLUE);
       g2d.draw(new Line2D.Double(300.0d,200.0d,x,y));
   }
   

   解決方案

   You have a couple of errors in your code (and logic):

   1. You're using 2 angles to calculate the X and Y coords, thus, giving you weird results. As per this Wikipedia image the angle theta is the same for bot coords.

   2. You're using the angle in degrees, but Math.cos(angle) and Math.sin(angle) require that the angle is given in radians, so, you must convert the angles to radians as like Math.roRadians(angle), as shown in this question: How to use Math.cos() & Math.sin()?

   3. Not really an error but a suggestion from @MadProgrammer in this other answer of mine to use the Shape API instead of pure .drawOval as you did while drawing the line, change drawOval to draw(new Ellipse2D.Double(...)).

   4. You're overriding paint(Graphics g) method instead of paintComponent(Graphics g) this could cause some issues while painting. Use JPanels and override their paintComponent method and add those JPanels to your JFrame.

   Having said all of the above, I came to a good example that follows the above advises as well as solving the issue:

   import java.awt.Color;
   import java.awt.Dimension;
   import java.awt.Graphics;
   import java.awt.Graphics2D;
   import java.awt.geom.Ellipse2D;
   import java.awt.geom.Line2D;
   
   import javax.swing.JFrame;
   import javax.swing.JPanel;
   import javax.swing.SwingUtilities;
   
   public class RadiusDrawer {
       private JFrame frame;
       private int centerX = 50;
       private int centerY = 50;
       private int x = 0;
       private int y = 0;
       private int r = 100;
   
       public static void main(String[] args) {
           SwingUtilities.invokeLater(new RadiusDrawer()::createAndShowGui);
       }
   
       private void createAndShowGui() {
           frame = new JFrame(getClass().getSimpleName());
   
           frame.add(new MyCircle());
           frame.pack();
           frame.setVisible(true);
           frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       }
   
       @SuppressWarnings("serial")
       class MyCircle extends JPanel {
           int cx = 0;
           int cy = 0;
           public MyCircle() {
               int angle = 0;
   
               x = (int) (r * Math.cos(Math.toRadians(angle)));
               y = (int) (r * Math.sin(Math.toRadians(angle)));
   
               y *= -1; //We must inverse the Y axis since in Math Y axis starts in the bottom while in Swing it starts at the top, in order to have or angles correctly displayed, we must inverse the axis
   
               calculateCenter();
           }
   
           private void calculateCenter() {
               cx = centerX + r;
               cy = centerY + r;
           }
   
           @Override
           protected void paintComponent(Graphics g) {
               super.paintComponent(g);
               Graphics2D g2d = (Graphics2D) g;
   
               drawCircle(g2d, centerX, centerY, r);
               drawRadius(g2d);
           }
   
           private void drawCircle(Graphics2D g2d, int x, int y, int r) {
               g2d.setColor(Color.BLACK);
               g2d.draw(new Ellipse2D.Double(x, y, r * 2, r * 2));
           }
   
           private void drawRadius(Graphics2D g2d) {
               g2d.setColor(Color.BLUE);
               g2d.draw(new Line2D.Double(cx, cy, cx + x, cy + y));
           }
   
           @Override
           public Dimension getPreferredSize() {
               return new Dimension(300, 300);
           }
       }
   }
   

   Here are some screenshots of the output at 0, 60 and 90 degrees.

   這篇關于如何在不小于或大于周長的情況下繪制圓的半徑的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！

   【網站聲明】本站部分內容來源于互聯網,旨在幫助大家更快的解決問題，如果有圖片或者內容侵犯了您的權益，請聯系我們刪除處理，感謝您的支持！