java - 找不到符号 Action 监听器引用变量

Question

这是我的第一个 GUI 程序，我似乎无法弄清楚为什么会出现此错误。我已将 actionListener 接口(interface)设置为 main.c 中的内部类。我尝试将所有引用该类的代码放在课后，但根据我读过的其他一些帖子，我没有运气。

Assig4.java:57: error: cannot find symbol  
        ActionListener listener2 = new MListener();  
                                         ^
  symbol:   class MListener  
  location: class Assig4      
  LINE 57 FOR REFERENCE: ActionListener listener2 = new MListener();

//import section
import java.awt.*;
import java.awt.event.*;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.*;
import javax.swing.*;


public class Assig4 {


    public static void main (String [] args) throws IOException
    {

        /* variables */

        String ballotsFile = args[0]; // gets the file name from command line
        JFrame theWindow; //assign variable name for main window
        ArrayList <Ballot> ballotsAr = new ArrayList<>(); //creates array for jpanel ballot objects

        int numBallots=0;
        int counter = 0; //to count each file read in loop
        JButton login, submitVote;
        //voter variables
        ArrayList <Integer> voterIdList = new ArrayList<>();
        ArrayList <String> voterNames = new ArrayList<>();
        ArrayList <Boolean> voterVoted = new ArrayList<>();

        /*create window*/

        theWindow = new JFrame ("Voting E Machine");
        theWindow.setLayout(new FlowLayout());

        /* read in ballot info and create ballot objects*/

        numBallots = readInBallotFile(ballotsFile, numBallots, ballotsAr);

        /*read in data from voter file*/

        try {
            // method that accesses the file
            readInVoterFile(voterIdList, voterNames, voterVoted);
        }
        catch (Exception e)
        {}

        /*create action listener object */
        ActionListener listener2 = new MListener();

        /*add Ballot panels*/
        addPanels(theWindow, ballotsAr);

        /*add local components*/
        submitVote = new JButton("Submit Vote(s)");
        submitVote.setEnabled(false);
        submitVote.addActionListener(listener2);
        login = new JButton("Login");
        login.addActionListener(listener2);
        theWindow.add(submitVote);
        theWindow.add(login);

        /*pack and set window to visible*/

        theWindow.pack();
        theWindow.setVisible(true);

        /*actionListener class to handle login and vote submissions*/

        class MListenter implements ActionListener
        {
            public void actionPerformed(ActionEvent ae)
            {
                //if submitVote button is clicked
                if (ae.getSource() == submitVote)
                {
                    //tally results
                    //update voter file local variables including false to true for voted
                    //write data to temp file
                    //delete original file
                    //change temp file name to previous file name
                }

                //if login button is clicked
                if (ae.getSource() == login)
                {

                    String userEntryIdString;
                    int userEntryId;
                    boolean registered=false;

                    do {
                        userEntryIdString = JOptionPane.showInputDialog("Enter your voter ID number: ");
                        userEntryId = Integer.parseInt(userEntryIdString);
                        //check id number against registered citizens
                        for (int v =0; v < voterIdList.size(); v++)
                        {
                            if (userEntryId == voterIdList.get(v))
                            {
                                registered = true;
                            }
                        }   // end of loop to check id against id list

                        if (registered)
                        {
                            //enable buttons
                            for (int j = 0; j<ballotsAr.size(); j++)
                            {
                                ballotsAr.get(j).enableCandidateButtons();
                            }
                            submitVote.setEnabled(true);
                        }

                        else if (!registered)
                            System.out.println("Invalid ID number. Please try again. ");
                    } while (!registered);
                } //end of if login button is clicked
            } //end of action performed method

        }// end of actionlistener

    }   //end of main

    public static int readInBallotFile(String ballotsFile, int numBallots, ArrayList<Ballot> ballotsAr) throws IOException
    {
        int counter = 0;
        //objects - open and setup scanner for file
        File myfile = new File (ballotsFile);
        Scanner textScan = new Scanner(myfile); // reads in date from text file
        numBallots = Integer.parseInt(textScan.nextLine()); //read in first line (number of ballots) and parse to int
        while (textScan.hasNextLine()) //one ballot's data for each loop
        {

            //read in each ballot's info
            //take the first line as a string
            String [] tempStr = textScan.nextLine().split(":");
            //parse line into proper data values
            int tempId = Integer.parseInt(tempStr[0]); //take first value for id
            String tempCategory = tempStr[1]; // take second value as category type
            String [] tempCandidates = tempStr[2].split(","); // takes the arbitrary number of candidates and splits into separate string variables

            //create ballot object
            ballotsAr.add(new Ballot(tempId,tempCategory,tempCandidates));
            counter++; //adds counter to while loop
        }   // end of loop to read in ballot text file contents
        textScan.close(); //closes ballots.txt file
        return numBallots;
    }   //end of read in ballot file method

    public static void addPanels(JFrame theWindow, ArrayList <Ballot> ballotsAr)
    {
        for (int i =0; i<ballotsAr.size();i++)
        {
            theWindow.add(ballotsAr.get(i));
        }
    }

    public static void readInVoterFile(ArrayList <Integer> _voterIdList, ArrayList <String> _voterNames, ArrayList <Boolean> _voterVoted) throws IOException
    {
        int counter = 0;
        //objects - open and setup scanner for file
        File myfile = new File ("voters.txt");
        Scanner textScan = new Scanner(myfile); // reads in date from text file
        while (textScan.hasNextLine()) //one voter's data for each loop
        {
            //take the first line as a string
            String [] tempStr = textScan.nextLine().split(":");
            //parse line into proper data values
            _voterIdList.add(Integer.parseInt(tempStr[0]));  //take first value for voter id
            _voterNames.add(tempStr[1]); // take second value as voter name
            _voterVoted.add(Boolean.parseBoolean(tempStr[2]));
            counter++; //adds counter to while loop
        }   // end of loop to read in voter text file contents
        textScan.close(); //closes ballots.txt file
    } // end of voter read in method

} // end of class

Answer 1

您拼错了其中一个。

ActionListener listener2 = new MListener();

class MListenter implements ActionListener

注意类名中额外的“t”。