学以致用——Java源码——绘制随机三角形（Random Triangles）

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程序功能：

绘制8个带有填充色的三角形（顶点（大小）随机、颜色随机）。

运行结果：

 

源码：

1. 实体类

//Creating JFrame to display DrawPanel.
import java.awt.Graphics2D;
import java.awt.Polygon;
import java.awt.geom.GeneralPath;
import java.security.SecureRandom;
import javax.swing.JPanel;
import java.awt.Color;
import java.awt.Graphics;

/**
 * 13.9 (Random Triangles) Write an application that displays randomly generated
 * triangles in different colors. Each triangle should be filled with a
 * different color. Use class GeneralPath and method fill of class Graphics2D to
 * draw the triangles.
 * 
 * @author [email protected]
 * @Date Jan 22, 2019, 15:44:03 PM
 *
 */
public class RandomTrianglesJPanel extends JPanel
{
	final SecureRandom rn = new SecureRandom();
	public void paint(Graphics g)
	{
	       Graphics2D g2d = (Graphics2D) g;	
		   super.paintComponents(g);
		   int width = getWidth(); // total width   
		   int height = getHeight(); // total height
		   int rRed=0;
		   int rGreen=0;
		   int rBlue=0;
		   
		   
		   //画8个三角形
		   for (int i = 8; i > 0;i--){
			   //Color represented in RGB mode
			   rRed = rn.nextInt(256);
			   rGreen = rn.nextInt(256);
			   rBlue = rn.nextInt(256);
			   Color color=new Color(rRed, rGreen, rBlue);
			   g2d.setColor(color);	//设置颜色
			  
			   
			   boolean triangleFound = false;
			   int[][] triangleCordinates = new int[2][3];
			   
			   do {
				   int aX = 1+rn.nextInt(width);
				   int aY = 1+rn.nextInt(height);
				   int bX = 1+rn.nextInt(width);
				   int bY = 1+rn.nextInt(height);
				   int cX = 1+rn.nextInt(width);
				   int cY = 1+rn.nextInt(height);
				   
				   double abL = Math.sqrt(Math.pow(Math.abs(aX-bX), 2)+Math.pow(Math.abs(aY-bY), 2));
				   double bcL = Math.sqrt(Math.pow(Math.abs(bX-cX), 2)+Math.pow(Math.abs(bY-cY), 2));
				   double acL = Math.sqrt(Math.pow(Math.abs(aX-cX), 2)+Math.pow(Math.abs(aY-cY), 2));   
			   	   
				   triangleCordinates[0][0] = aX;	//A点X坐标
				   triangleCordinates[0][1] = bX;	//B点X坐标
				   triangleCordinates[0][2] = cX;	//C点X坐标
				   triangleCordinates[1][0] = aY;	//A点Y坐标
				   triangleCordinates[1][1] = bY;	//B点Y坐标
				   triangleCordinates[1][2] = cY;	//C点Y坐标

			   if (abL+bcL>acL && abL+acL>bcL && bcL+acL>abL)	//三角形判定法则：任意两边之和大于第三边
				   triangleFound = true;
			   } while (!triangleFound); //如果随机生成的坐标无法构成三角形，则继续随机构造
			   
			   g2d.fill(new GeneralPath(new Polygon(triangleCordinates[0],triangleCordinates[1],3)));	//绘制三角形

			   }	   

	}
		
} 

2. 测试类

import java.awt.BorderLayout;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import javax.swing.JFrame;
import javax.swing.JTextArea;



public class DrawRandomTriangles {
	
	static JTextArea statusBar = new JTextArea();
	
	public static void main(String[] args)
	{
	 // create a panel that contains our drawing
		RandomTrianglesJPanel panel = new RandomTrianglesJPanel();
		
		MouseHandler handler = new MouseHandler(); 
		panel.addMouseMotionListener(handler);

		
	 // create a new frame to hold the panel
	 JFrame application = new JFrame();
	 application.setTitle("绘制随机三角形");
	 
	 // set the frame to exit when it is closed
	 application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	 
	 application.add(panel,BorderLayout.CENTER); // add the panel to the frame
	 application.add(statusBar,BorderLayout.SOUTH); // add the statusBar to the frame
	 application.setSize(460, 360); // set the size of the frame
	 application.setVisible(true); // make the frame visible    
	} 
	
	static class MouseHandler extends  MouseMotionAdapter 
	{
	   
	   // handle event when mouse enters area
		@Override
	   public void mouseMoved(MouseEvent event)
	   {  
			 statusBar.setText(String.format("光标当前坐标：[%d, %d]", 
		 	            event.getX(), event.getY()));;
	   }

	}
	

}