app18_12.java

这是大学里的 java课后题的答案

// app18_12,拖拽鼠标绘图
import java.awt.*;  
import java.awt.event.*; 
public class app18_12 extends Frame implements MouseMotionListener,MouseListener
{
   static app18_12 frm=new app18_12();
  static private int x1[],y1[];
    private  int i=0;
    private  int k;
   boolean  t=false;
   public static void main(String args[])
   {
      frm.setTitle("Free drawing");
      frm.setSize(200,150);  
      frm.addMouseListener(frm);  // 设置MouseListener
      frm.addMouseMotionListener(frm); // 设置MouseMotionListener
      frm.setVisible(true);  
   }
   public void mousePressed(MouseEvent e)
   {
      x1[i]=e.getX();   // 取得鼠标按下时的X坐标 (绘图起始点是X坐标)
      y1[i]=e.getY();   // 取得鼠标按下时的Y坐标 (绘图起始点是Y坐标)
   }
   public void mouseDragged(MouseEvent e)
   {
      Graphics g=getGraphics(); 
      x1[i+1]=e.getX();  // 取得鼠标拖拽时的X坐标
      y1[i+1]=e.getY();  // 取得鼠标拖拽时的Y坐标
      g.drawLine(x1[i],y1[i],x1[i+1],y1[i+1]);  // 绘出(x1,y1)到(x2,y2)的连线
      x1[i]=x1[i+1];  // 更新绘图起始点的X坐标
      y1[i]=y1[i+1];  // 更新绘图起始点的Y坐标 
   } 
   	public void  paint(Graphics g)
   	{ 
   		int j;
   		if(t==true)
   			for(j=0;j<k;j++)
   				g.drawLine(x1[i],y1[i],x1[i+1],y1[i+1]);
   			
   	}
   public void mouseMoved(MouseEvent e){} 
   public void mouseReleased(MouseEvent e){
   	t=true;
   	k=i;
   	} 
   public void mouseEntered(MouseEvent e){} 
   public void mouseExited(MouseEvent e){} 
   public void mouseClicked(MouseEvent e){} 
}