example4_14.java

书中的例题

/* 居中显示的窗体 */
import java.awt.*;
import java.awt.event.*;

public  class Example4_14 extends Frame implements ActionListener
 {
   Toolkit tool;
   Button btn;
   TextArea txt;
   Example4_14()
	{
	 //设置窗体的标题
	 super("窗体演示");
	 //建立Toolkit对象
	 tool = getToolkit();
     //获得屏幕大小
	 Dimension screen = tool.getScreenSize();
	 //设置窗口宽和高为屏幕大小的一半
	 setSize((screen.width)/2,(screen.height)/2);
     //使窗口居中显示
     setLocation((screen.width - getSize().width) / 2,
	          (screen.height - getSize().height) / 2); 
	 //显示窗体
	 show();
     btn=new Button("关闭窗口");
     add(btn,BorderLayout.SOUTH);
     txt = new TextArea(5,5);
	 add(txt,BorderLayout.CENTER);
	 validate();
	 btn.addActionListener(this);
    }

  public void actionPerformed(ActionEvent e)
   {
     System.exit(0);
   }

  public static void main(String[] args)
   {
    new Example4_14();
   }
}