app18_3.java

这是大学里的 java课后题的答案

// app18_1, 简单的绘图
import java.awt.*;  
import java.awt.event.*;
public class app18_3 extends Frame implements ActionListener
{
   static app18_3 frm=new app18_3();
   static Button btn=new Button("Draw");
   static Button btn1=new Button("Clear");
   static Panel pal=new Panel();
   public static void main(String args[])
   {
      BorderLayout br=new BorderLayout();
      frm.setTitle("Drawing example");
      frm.setLayout(br);
      frm.setSize(200,150);
      pal.add(btn);
      pal.add(btn1);
      frm.add(pal,br.SOUTH);
      btn.addActionListener(frm);
      btn1.addActionListener(frm);
      frm.show();
   }
   public void actionPerformed(ActionEvent e)
   {
   	if(e.getSource()==btn)
   	{Graphics g=getGraphics();  // 取得窗口的绘图区
      g.drawRect(100,50,70,55);  // 绘出长方形
   }
   else if(e.getSource()==btn1)
   {Graphics g=getGraphics();
   	update(g);
   }
   }
   public void paint(Graphics g)
   {
   }
}