example7_18.java

不错的教程 适合中高级人员的使用

import java.awt.*;
import java.awt.event.*;
class Mycanvas extends Canvas 
{  int x,y,r;
   int red,green,blue;
   Mycanvas() 
   {  
      setBackground(Color.cyan);
   }
   public void setX(int x)
   {  this.x=x; 
   }
   public void setY(int y)
   { this.y=y;
   }
   public void setR(int r)
   { this.r=r;
   }
   public void paint(Graphics g)
   {  g.drawOval(x,y,2*r,2*r);
   }
} 
class WindowCanvas extends Frame implements ActionListener
{  Mycanvas canvas;
   TextField inputR,inputX,inputY;
   Button b;
   WindowCanvas() 
   {  canvas=new Mycanvas();
      inputR=new TextField(5);
      inputX=new TextField(4);
      inputY=new TextField(4);
	  Panel pSouth=new Panel(),pNorth=new Panel();
      pNorth.add(new Label("圆的位置坐标："));
      pNorth.add(inputX);
      pNorth.add(inputY);
      pSouth.add(new Label("圆的半径："));
      pSouth.add(inputR);
      b=new Button("确定");
      b.addActionListener(this);
      pSouth.add(b); 
      add(canvas,BorderLayout.CENTER);
	  add(pNorth,BorderLayout.NORTH);
	  add(pSouth,BorderLayout.SOUTH);
	  setBounds(100,100,300,200);
	 setVisible(true);
	 validate();
   } 
   public void actionPerformed(ActionEvent e)
   {  int x,y,r;
      try {
             x=Integer.parseInt(inputX.getText());
             y=Integer.parseInt(inputY.getText());
             r=Integer.parseInt(inputR.getText());
             canvas.setX(x);
             canvas.setY(y);
             canvas.setR(r);
             canvas.repaint();
           }
      catch(NumberFormatException ee)
           { 
             x=0;y=0;r=0;
           }
   }
}
public class Example7_18
{
	public static void main(String[] args) 
	{
		new WindowCanvas();
	}
}