按钮上添加的键盘监听无法奏效

import java.awt.Button;

import java.awt.FlowLayout;

import java.awt.Frame;

import java.awt.event.KeyAdapter;

import java.awt.event.KeyEvent;

import java.awt.event.WindowAdapter;

import java.awt.event.WindowEvent;

public class Keyboard_events {



     // 定义该图形所需的组件的引用

    private Frame f;

    private Button but;



    Keyboard_events(){



        init();



    }



    // 对图形用户界面初始化

    public void init() {



        f = new Frame("窗口——by星云");

        f.setBounds(300, 100, 600, 500); // 设置窗口位置和大小

        f.setLayout(new FlowLayout());// 默认边界布局方式重置成流式布局



        but = new Button("我是按钮");

        f.add(but);

        

        dealwithEvent();



        f.setVisible(true);

    }



    //事件监听器以及处理事件

    private void dealwithEvent()

    {

         

        //窗体关闭监听

         f.addWindowListener(new WindowAdapter(){

             public void windowClosing(WindowEvent e){

                 System.exit(0);

                 

             }

             

         });

         

        //键盘监听

         but.addKeyListener(new KeyAdapter(){

        	 public void keypressed(KeyEvent e)

        	 {

        		 //System.out.println(KeyEvent.getKeyText(e.getKeyCode())+"......."+e.getKeyCode());

        	 }

         });

        

    }

  

    public static void main(String[] args) {



          new Keyboard_events();

    }



}