以下是我的程序。目的是在用户键入数字并按Enter键之后，将罗马数字转换为阿拉伯数字。

这是一项家庭作业，我们被迫JTextAreas代替JTextFields。

线路中存在我的错误：enterRomanNumber.addActionListener(handler); 该错误显示为：

“对于类型JTextArea，未定义方法addActionListener（ArabicToRomanGUI.HandlerForTextArea）”

我似乎无法弄清楚为什么会收到此错误或如何纠正它，有人可以建议一下。

import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class ArabicToRomanGUI extends JFrame
{
private static final long serialVersionUID = 1L;
private JTextArea enterRomanNumber = new JTextArea();
JLabel label = new JLabel();
JPanel panel = new JPanel();
JFrame frame = new JFrame();


//TestArea contructor adds jtextArea to jframe
public ArabicToRomanGUI()
{
    super("Convert a Roman Numeral");
    setLayout(new FlowLayout());

    //Text field to enter a roman numeral
    enterRomanNumber = new JTextArea(1,25);
    enterRomanNumber.setText("Delete this text and Enter a Roman Numerial Here!");
    //enterRomanNumber.setAlignmentX(0);
    //enterRomanNumber.setAlignmentY(0);

    add(enterRomanNumber);

    HandlerForTextArea handler = new HandlerForTextArea();
    enterRomanNumber.addActionListener(handler);
}

private class HandlerForTextArea implements ActionListener
{
    //used to process textArea events
    @Override
    public void actionPerformed(ActionEvent e) 
    {
        String userInput = "";
        userInput = enterRomanNumber.getText();
        userInput = userInput.toUpperCase();

        ConversionLogic.ConvertFromRomanToArabic(userInput); //converts user string of Roman numerals to an int in arabic
        String arabicNumberAsString = ConversionLogic.getConvertedRomanNumeral();
        enterRomanNumber.setText(arabicNumberAsString);

        //user pressed enter in JTextField enterNumberField
        if(e.getSource() == enterRomanNumber)
        {
            //enterRomanNumber.setText(arabicNumberAsString);
            if (ConversionLogic.getCheckFail() == true)
            {
                JOptionPane.showMessageDialog(frame, "The Roman Numeral entered is Invalid", "Error", JOptionPane.ERROR_MESSAGE);
            }
            else
            {
                JOptionPane.showMessageDialog(frame, "The arabic equivalent is " + arabicNumberAsString + "." , "Conversion Successful", JOptionPane.PLAIN_MESSAGE);
            }
        }

    }
}
}//end inner class TextAreaHandler