利用Graphics类做的一些习题（四）

旧城等待， 2023-08-17 17:42 42阅读 0赞

# 效果 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNTc2MDI4_size_16_color_FFFFFF_t_70]

# 题目 #

\*\*15.11（绘图表示平方的函数）编写程序，绘制函数f(x)=x^2的图形

# 代码 #

package Test;
    
    import javax.swing.*;
    import java.awt.*;
    
    public class Exercise15_11 extends JFrame {
        
        public Exercise15_11(){
        
           add(new drawFunc());
        }
    
        public static void main(String[] args) {
        
            Exercise15_11 frame=new Exercise15_11();
            frame.setTitle("Exercise16_9");
            frame.setSize(800,400);
            frame.setLocationRelativeTo(null);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
        }
    }
    
    class drawFunc extends JPanel{
        
        @Override
        protected void paintComponent(Graphics g) {
        
            super.paintComponent(g);
            //x轴
            g.drawLine(50,200,400,200);
            //y轴
            g.drawLine(200,50,200,400);
            //x轴箭头
            g.drawLine(400,200,400-17,200-17);
            g.drawLine(400,200,400-17,200+17);
            //y轴箭头
            g.drawLine(200,50,200-17,50+17);
            g.drawLine(200,50,200+17,50+17);
            //x轴文字
            g.drawString("x",410,200);
            //y轴文字
            g.drawString("y",210,50);
    
            Polygon p=new Polygon();
            double scaleFactor=0.01;
            for (int x = -100 ; x <=100 ; x++) {
        
                p.addPoint(x+200,200-(int)(scaleFactor*x*x));
            }
            g.drawPolyline(p.xpoints,p.ypoints,p.npoints);
        }
    }

# 思路解析 #

使用下面的 循环在多边形p中加入点

Polygon p=new Polygon();
            double scaleFactor=0.01;
            for (int x = -100 ; x <=100 ; x++) {
        
                p.addPoint(x+200,200-(int)(scaleFactor*x*x));
            }
            g.drawPolyline(p.xpoints,p.ypoints,p.npoints);

对Graphics对象g使用 g.drawPolyline(p.xpoints,p.ypoints,p.npoints)来连接点，p.xpoints返回x坐标的数组，p.ypoints返回y坐标的数组，p.npoints返回Polygon对象p的点的个数。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzNTc2MDI4_size_16_color_FFFFFF_t_70]: /images/20230808/3cc825f02bd6451ba9a11c77d889cd46.png