帮我看看问题在哪儿
public class E4 extends JFrame{
 private JDialog jd;
 private JButton jb;
 private JLabel jl;
 public E4(){
 JFrame jf=new JFrame("事件");
 jb=new JButton("开始");
 jl=new JLabel("结果");
 jd=new JDialog(this,"对话框",true);
 jd.setBounds(200,200,200,200);
 JTextField jta=new JTextField("");
 String s=jta.getText();
 jl.setText(s);
 jb.addActionListener(new MyListener());
 jf.setLayout(new FlowLayout());
 jf.add(jb);
 jd.add(jl);
 jf.add(jta);
 setBounds(400,400,400,400);
 jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 jf.setSize(400,400);
 jf.setVisible(true);
 }
 class MyListener implements ActionListener{
 public void actionPerformed(ActionEvent e){
 jd.setVisible(true);
 }}
 public static void main(String[] args) {
 // TODO Auto-generated method stub
  new E4();
 }

一个小练习，在文本域输入字符，然后在JDialog显示刚才输入的字符，可是这个程序的结果是JDialog没显示刚才输入的结果，求大神指点

------解决方案--------------------
public class E4 extends JFrame {
private JDialog jd;
private JButton jb;
private JLabel jl;
private JTextField jta;
public E4() {
JFrame jf = new JFrame("事件");
jb = new JButton("开始");
jl = new JLabel("结果");
jd = new JDialog(this, "对话框", true);
jd.setBounds(200, 200, 200, 200);
jta = new JTextField(10);
jb.addActionListener(new MyListener());
jf.setLayout(new FlowLayout());
jf.add(jb);
jf.add(jta);
setBounds(400, 400, 400, 400);
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.setSize(400, 400);
jf.setVisible(true);
}

class MyListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
jl = new JLabel("结果");
jl.setText(jta.getText());
jd.add(jl);
jd.setVisible(true);
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
new E4();
}
}

------解决方案--------------------
楼上正解，你的

Java code

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class E4 extends JFrame {
    private JDialog jd;
    private JButton jb;
    private JLabel jl;
    private JTextField jta ; //把这个放出来 ，因为你的点击事件重要取出来

    public E4() {
        JFrame jf = new JFrame("事件");
        jb = new JButton("开始");
        jl = new JLabel("结果");
        jd = new JDialog(this, "对话框", true);
        jd.setBounds(100, 100, 200, 200);
        jta = new JTextField(15);
        String s = jta.getText();
        jl.setText(s);
        jb.addActionListener(new MyListener());
        jf.setLayout(new FlowLayout());
        jf.add(jb);
//        jd.add(jl); //这时候还没有数据 ，可以不要放上去
        jf.add(jta);
        setBounds(400, 400, 400, 400);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setSize(400, 400);
        jf.setVisible(true);
    }

    class MyListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            jl.setText(jta.getText());//设置完数据
            jd.add(jl); //加到对话框上
            jd.setVisible(true);

        }
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new E4();
    }
}