/*
列出指定目录内容
*/
import java.awt.*;
import java.awt.event.*;
class  MyWindowDemo
{
private Frame f;
private TextField tf;
private Button but;
private TextArea ta;
private Dialog d;//新建一个对话框
private Label lab;//新建一个标签
private Button okBut;
MyWindowDemo()
{
           init();
}
public void init()
{
  f=new Frame("my window");
  f.setBounds(300,100,600,500);
  f.setLayout(new FlowLayout());
  tf=new TextField(60);
  but=new Button("转到");
  ta=new TextArea(25,70);
  d=new Dialog(f,"提示信息-self",true);//新建对话框
  d.setBounds(400,200,240,150);
  d.setLayout(new FlowLayout());
  lab=new Label();//新建标签
  okBut=new Button("确定");
  d.add(lab);
  d.add(okBut);
  f.add(tf);
  f.add(but);
  f.add(ta);
  myEvent();
  f.setVisible(true);
}
public void myEvent()
{
  okBuf.addWindowListener(new WindowAdapter()
   {
    public void actionPerformed(ActionEvent e)
    {
     d.setVisible(false);
    }
   });
  d.addWindowListener(new WindowAdapter()
  {
   public void windowClosing(WindowEvent e)
   {
     d.setVisible(false);
   }
  });
  
   
  but.addActionListener(new ActionListener()
  {
   public void actionPerformed(ActionEvent e)
   {
    String dirPath=tf.getText();//获取文本框内容
    File dir=new File(dirPath);//创建文件对象
    if(dir.exists()&&dir.isDirectory())
    {
     ta.setText("");
     String[]names=dir.list();
     for(String name:names)
     {
      ta.append(name+"\r\n");
     }
    }
    else
    {
     d.setVisible(true);
    }
   
    //public void windowClosing(WindowEvent e)
    // {
    //  System.exit(0);
    // }
    }
   });
   }
}

}
class  LabelTest
{
public static void main(String[] args)
{
  new MyWindowDemo();
  //System.out.println("Hello World!");
}
}

疑问：运行时总是报错，不知是哪里的问题。

楼主,我已经帮你修改好了,在我这里已经能够正常运行了.

望采纳.你写错的地方我已经用红色标识出来了. /*
列出指定目录内容
*/
import java.awt.Button;
import java.awt.Dialog;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Label;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.File;

class MyWindowDemo {
private Frame f;
private TextField tf;
private Button but;
private TextArea ta;
private Dialog d;// 新建一个对话框
private Label lab;// 新建一个标签
private Button okBut;

MyWindowDemo() {
init();
}

public void init() {
f = new Frame("my window");
f.setBounds(300, 100, 600, 500);
f.setLayout(new FlowLayout());
tf = new TextField(60);
but = new Button("转到");
ta = new TextArea(25, 70);
d = new Dialog(f, "提示信息-self", true);// 新建对话框
d.setBounds(400, 200, 240, 150);
d.setLayout(new FlowLayout());
lab = new Label();// 新建标签
okBut = new Button("确定");
d.add(lab);
d.add(okBut);
f.add(tf);
f.add(but);
f.add(ta);
myEvent();
f.setVisible(true);
}

public void myEvent() {
  f.addWindowListener(new WindowAdapter() {     // 给窗体添加窗体监听器,给你多加一个用于关闭窗口的监听器.挺重要的.
   public void windowClosing(WindowEvent e) {
    System.exit(0);
   }
  });

okBut.addActionListener(new ActionListener() {    //这里的okBut你写成okBuf了,同时按钮要添加的是动作监听器,而不是窗口监听器
public void actionPerformed(ActionEvent e) {
d.setVisible(false);
}
});
d.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
d.setVisible(false);
}
});

but.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String dirPath = tf.getText();// 获取文本框内容
File dir = new File(dirPath);// 创建文件对象
if (dir.exists() && dir.isDirectory()) {
ta.setText("");
String[] names = dir.list();
for (String name : names) {
ta.append(name + "\r\n");
}
} else {
d.setVisible(true);
}

// public void windowClosing(WindowEvent e)
// {
// System.exit(0);
// }
}
});
}
} //楼主之前这里多了一个大括号,我已经去掉了

class LabelTest {
public static void main(String[] args) {
new MyWindowDemo();
}
}

附:运行图:

此问题已解决~