学以致用——Java源码——使用Line2D.Double类绘制随机线段（Random Lines Using Class Line2D.Double）

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程序功能：

显示8条线段（颜色随机，位置随机，线段粗度随机）。

运行结果：

源码：

1. 实体类

/**
 * 13.8 (Random Lines Using Class Line2D.Double) Modify your solution to
 * Exercise 13.7 to draw random lines in random colors and random thicknesses.
 * Use class Line2D.Double and method draw of class Graphics2D to draw the
 * lines.
 * 
 * @author [email protected]
 * @Date Jan 22, 2019, 1:44:03 PM
 *
 */
public class RandomLinesJPanel extends JPanel
{
 
	public void paint(Graphics g)
	{
	       Graphics2D g2d = (Graphics2D) g;	
		   super.paintComponents(g);
		   double width = getWidth(); // total width   
		   double height = getHeight(); // total height
		   int rRed=0;
		   int rGreen=0;
		   int rBlue=0;
	
		   final SecureRandom rn = new SecureRandom();
		   
		   //画8个同心圆，每个同心圆相距10个像素
		   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);	//设置线段颜色
			   
			   double startX = 1+width*rn.nextDouble();
			   double startY = 1+height*rn.nextDouble();
			   double endX = 1+width*rn.nextDouble();
			   double endY = 1+height*rn.nextDouble();
			   float thickness =  (float) 1 + rn.nextInt(20);
			   g2d.setStroke(new BasicStroke(thickness));  //设置线段的粗细
			   g2d.draw(new Line2D.Double(startX, startY, 
					   endX,  endY));	//绘制线段

			   }	   

	}
		
} 

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

		
	 // create a new frame to hold the panel
	 JFrame application = new JFrame();
	 application.setTitle("使用Ellipse2D.Double类绘制同心圆");
	 
	 // 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()));;
	   }

	}
	

}