Java无法识别已定义的变量？

Question

在actionPerformed中，似乎所有变量（submit、msg、input）都无法根据Eclipse进行解析。根据我的经验（我几乎没有经验），这意味着我没有定义变量。但是，正如你在代码中看到的，我已经定义了它们。Submit是一个JButton，msg是一个字符串，input是一个JTextField

package levels;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

import java.util.*;

public class LevelOne extends JFrame implements ActionListener{

    private Object msg;

    public void one(){

        setTitle("Conjugator");
        setSize(400,400);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);

        setLayout(new BorderLayout());
        setContentPane(new JLabel(new ImageIcon("images/LevelOneBG.gif")));
        setLayout(new FlowLayout());

        JTextArea area = new JTextArea("You enter a castle. A Goblin demands you correct his sentences!");
        add(area);
        setVisible(true);

        //these aren't being called to actionPerformed
        JButton submit = new JButton("Check sentence");
        submit.addActionListener(this);
        setVisible(true);
        JTextField input = new JTextField("Ich spielen Golf.");
        input.setActionCommand("input");
        add(input);
        input.addActionListener(this);
        setVisible(true);

        String msg = ("Test successful");
    }   

    //this should be successfully locating and utilizing "submit", "input" and "msg", but it won't
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == submit) {
            msg = submit.getText();

            //!!  Display msg only **after** the user has pressed enter.
            input.setText(msg); 
        }

    }
}

我知道我的一些进口商品是不必要的

另外，我正在为我的德语课做一个小的文本冒险游戏

Answer 1

这些变量的作用域仅为one（）方法。如果你想让全班同学都能看到，就把它们放在最上面的味精旁边

Answer 2

变量submit在方法one()中定义为局部变量

它在方法actionPerformed()中不可用