请教 这段程序 键盘监听 怎么无效？谢谢

[thomson336]

请教 这段程序 键盘监听 怎么无效？谢谢

import java.applet.Applet;
import java.awt.Graphics;
import java.awt.event.*;

public class TestKeyListener extends Applet implements KeyListener {
int x=20;
public void init() {
addKeyListener(this);
}
public void paint(Graphics g){
//g.drawString("x is "+x,x,40) ;
g.drawString("A",x,40) ;
}

public void keyTyped(KeyEvent e) {
if(e.getKeyChar()=='r'||e.getKeyChar()=='R'){
x += 20;
repaint();
}
}

public void keyReleased( KeyEvent e ) {}
public void keyPressed( KeyEvent e ) {}
}




<applet code=TestKeyListener.class width=400 height=200>
</applet>

[cursor_wang]

给你个例子看下．

import java.awt.*;
import java.awt.event.*;

public class Sample_11_5_2 extends Frame
  implements KeyListener {

  String msg = "";
  int X = 20, Y = 50; 

  public Sample_11_5_2() {
    addKeyListener(this);
    requestFocus();     //请求获得输入焦点
  }

	//处理键盘按钮按下事件
  public void keyPressed(KeyEvent ke) {
    //msg="按下按键";
    //repaint();
  }

  //处理键盘按钮松开事件
  public void keyReleased(KeyEvent ke) {
    //msg+="，松开按键";
    //repaint();
  }

  //处理键盘字符按钮事件
public void keyTyped(KeyEvent ke) {
    msg += ke.getKeyChar();
    repaint();
  }

  // 显示记录信息
  public void paint(Graphics g) {
    g.drawString(msg, X, Y);
  }    
  
  public static void main(String[] args){
  	Sample_11_5_2 s=new Sample_11_5_2();
  	s.setSize(300,100);
  	s.setVisible(true);
  }
}

[hl4967]

这段程序没有问题,主要是你没有让当前的光标焦点到你的Applet上,根据JAVA消息的机制,如果不是他的事件源,他是不会被回调消息的处理方法的.