关于swing绘制余弦函数图形

Question

本帖最后由 hqjma 于 2012-04-05 15:49:17 编辑

Answer 1

为啥要用 drawString 呢？为了能够显眼？供你参考：
思路很简单，以deltaT为递进。
然后 x = fnX(t); y = fnY(t);
最后就是画线了，从 oldX,oldY -> X,Y 
public class DrawSin extends JFrame {    private static int SCALE_X = 20;
    private static int SCALE_Y = 50;        public void paint(Graphics g) {
        super.paint(g);        
        double ox = 0, oy = 0, x = 0, y = 0, t = 0;
        int middleY = this.getHeight()/2;
        for (t = 0; t < 50; t += 0.1) {
            x = t * SCALE_X;
            y = Math.sin(t) * SCALE_Y + middleY;
            if (t > 0) {
                g.drawLine((int) ox, (int) oy, (int) x, (int) y);
            }
            ox = x;
            oy = y;
        }
    }    public static void main(String[] args) {
        DrawSin wnd = new DrawSin();
        wnd.setSize(600, 500);
        wnd.setVisible(true);
    }
}

Answer 2

这个应该用点来描吧？送给你一个用 Java 输出控制台的余弦图像：###                                             #####                                             ### 
    ##                                         ##  |  ##                                         ##    
      #                                       #    |    #                                       #      
       #                                     #     |     #                                     #       
        #                                   #      |      #                                   #        
                                                   |                                                   
         #                                 #       |       #                                 #         
          #                               #        |        #                               #          
           #                             #         |         #                             #           
                                                   |                                                   
            #                           #          |          #                           #            
             #                         #           |           #                         #             
 --------------------------------------------------+-------------------------------------------------- 
              #                       #            |            #                       #              
               #                     #             |             #                     #               
                                                   |                                                   
                #                   #              |              #                   #                
                 #                 #               |               #                 #                 
                  #               #                |                #               #                  
                                                   |                                                   
                   #             #                 |                 #             #                   
                    #           #                  |                  #           #                    
                     #         #                   |                   #         #                     
                      ##     ##                    |                    ##     ##                      
                        #####                      |                      #####                       

Answer 3

看看这个吧package ex15;
import java.awt.*;
import javax.swing.*;public class Ex15_12 extends JFrame{
public Ex15_12(){
add(new DrawSine());
}
public static void main(String[] args) {
// TODO 自动生成方法存根
Ex15_12 frame=new Ex15_12();
frame.setTitle("Ex15_12");
frame.setSize(400,250);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}}class DrawSine extends JPanel{
double f(double x){
return Math.sin(x);
}

protected void paintComponent(Graphics g){
super.paintComponent(g);

Polygon p=new Polygon();
int xCenter=getWidth()/2;
int yCenter=getHeight()/2;

//画水平轴
g.drawLine(50,yCenter,xCenter+150,yCenter);
g.drawLine(xCenter+150, yCenter, xCenter+140, yCenter-10);
g.drawLine(xCenter+150, yCenter, xCenter+140, yCenter+10);

//画纵轴
g.drawLine(xCenter , yCenter+75, xCenter, yCenter-75);
g.drawLine(xCenter, yCenter-75, xCenter-10, yCenter-65);
g.drawLine(xCenter, yCenter-75, xCenter+10, yCenter-65);

g.drawString("-2\u03c0", xCenter-100, yCenter+10);
g.drawString("2\u03c0", xCenter+100, yCenter+10);

g.drawString("Y", xCenter+10, yCenter-75);
g.drawString("X", xCenter+140, yCenter-10);

for(int x=-100;x<=100;x++){
p.addPoint(x+xCenter, 
yCenter-(int)(50*f((x/100.0)*2*Math.PI)));
}
g.drawPolygon(p);
}
}

Answer 4

请问能不能具体分析下cos里面的参数究竟要不要乘以Math.PI/180之类的东西？网上貌似都没搜到这方面的资料。。

Answer 5

能不能分析下给f传参时，为什么要先(x/100.0)*2*Math.PI)，*2*PI是什么原理
我那个加上一个偏移值就可以成为标准函数曲线了，但有没有科学严谨点的方法？

Answer 6

我把坐标轴加上去了，没发现有任何偏移，请问你所说的偏移，具体是指什么偏移到什么了？
public class DrawSin extends JFrame {    private static int SCALE_X = 40; // X轴缩放倍数
    private static int SCALE_Y = 100; // Y轴缩放倍数
    private static int ORIGIN_X = 50; // 原点X 
    private static int ORIGIN_Y = 0; // 原点Y 
    private static int END_ARC = 360 * 2; // 画多长    public void paint(Graphics g) {
        double ox = 0, oy = 0, x = 0, y = 0, arc = 0;
        super.paint(g);        ORIGIN_Y = this.getHeight() / 2;        // 画坐标轴
        g.drawLine(ORIGIN_X, ORIGIN_Y, this.getWidth(), ORIGIN_Y); // 横轴
        g.drawLine(ORIGIN_X, 0, ORIGIN_X, this.getHeight()); // 纵轴
        // 每90度画个标尺
        for (int i = 0; i < END_ARC; i += 90) {
            arc = Math.PI * i * 2 / 360;
            x = ORIGIN_X + arc * SCALE_X;
            g.drawLine((int) x, ORIGIN_Y - 10, (int) x, ORIGIN_Y + 10);
        }        // 画正弦曲线
        g.setColor(Color.RED);
        for (int i = 0; i < END_ARC; i += 10) {
            arc = Math.PI * i * 2 / 360;
            x = ORIGIN_X + arc * SCALE_X;
            y = ORIGIN_Y + Math.sin(arc) * SCALE_Y;
            if (arc > 0) {
                g.drawLine((int) ox, (int) oy, (int) x, (int) y);
            }
            ox = x;
            oy = y;
        }
    }    public static void main(String[] args) {
        DrawSin wnd = new DrawSin();
        wnd.setSize(600, 500);
        wnd.setVisible(true);
    }
}