我的JButton的ActionListener如何访问另一个类中的变量？

Question

I am doing a slot machine for a project. I am having trouble getting my JButton to generate new random numbers from my ArrayList . I can randomize the numbers when the program starts and have an actionlistener set up, but it doesn't do what I need. It was merely for testing purposes.

My Actionlistener is in a different Java file. Everything works, I just can't figure out how to generate new randoms in the placeholder of plc1 , plc2 , and plc3 when the button is clicked.

I have just recently began to really code as about 3 weeks ago. No haters please, this is my first project ever.

package GGCGuiLotto;

import java.util.ArrayList;
import java.awt.Color;
import java.awt.Image;
import java.awt.BorderLayout; 
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.Icon;
import javax.swing.JOptionPane;
import javax.swing.JLabel;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JTextField;

import java.util.Random;


public class GGCGuiLotto {

public static void main(String[] args) {    

//Arraylist of images

ImageIcon pic0 = new ImageIcon("pics/pic1.png");
ImageIcon pic1 = new ImageIcon("pics/pic2.png");
ImageIcon pic2 = new ImageIcon("pics/pic3.png");
ImageIcon pic3 = new ImageIcon("pics/pic4.png");
ImageIcon pic4 = new ImageIcon("pics/pic5.png");
ImageIcon pic5 = new ImageIcon("pics/pic6.png");
ImageIcon pic6 = new ImageIcon("pics/pic7.png");

final ArrayList<ImageIcon> slotlist = new ArrayList<ImageIcon>();   
    slotlist.add(pic0);
    slotlist.add(pic1);
    slotlist.add(pic2);
    slotlist.add(pic3);
    slotlist.add(pic4);
    slotlist.add(pic5);
    slotlist.add(pic6);

    Random ran = new Random();

    int plc1 = ran.nextInt(4);
    int plc2 = ran.nextInt(4);
    int plc3 = ran.nextInt(4);

    //generates the frame and the labels are added.

    JFrame frame = new JFrame();
    frame.setSize (400,275);
    frame.setTitle("GGC Lotto Slots Rcorbin");
    frame.setResizable(false);
    frame.setVisible(true);

    JPanel pnlReels = new JPanel();
    frame.add(pnlReels);

    JPanel aReel1 = new JPanel();
    aReel1.setBackground(new Color(25,25,112));
    aReel1.setBounds(15,10,100,100);

    JPanel bReel2 = new JPanel();
    bReel2.setBackground(new Color(25,25,112));
    bReel2.setBounds(145,10,100,100);

    JPanel cReel3 = new JPanel();
    cReel3.setBackground(new Color(25,25,112));
    cReel3.setBounds(275,10,100,100);   

        pnlReels.add(aReel1);
    pnlReels.add(bReel2);
    pnlReels.add(cReel3);   

    JLabel aReel1lbl = new JLabel();
    JLabel bReel2lbl = new JLabel();
    JLabel cReel3lbl = new JLabel();

    aReel1.add(aReel1lbl);
    bReel2.add(bReel2lbl);
    cReel3.add(cReel3lbl);  

    aReel1lbl.setIcon(slotlist.get(plc1));
    bReel2lbl.setIcon(slotlist.get(plc2));
    cReel3lbl.setIcon(slotlist.get(plc3));  

    //jbutton 
    JButton slotbtn1 = new JButton();
    slotbtn1.setText("GGC LOTTO Click ME");
    pnlReels.add(slotbtn1);
    slotbtn1.setBounds(145,50,100,75);
    //FirstGuiListener act = new FirstGuiListener();
    //slotbtn1.addActionListener((ActionListener) act); 

GenPLCListener genPLC = new GenPLCListener();
slotbtn1.addActionListener((genPLC));
    {}
    if (plc1 == plc2 && plc1 == plc3 && plc2 == plc3)
    {
        JOptionPane.showConfirmDialog(null,"Winner! Play Again? ","GGC Lotto Slots RCorbin ",JOptionPane.YES_NO_OPTION);
        //System.out.println("Winner");
    }
    else
    {
        //JOptionPane.showMessageDialog(null,"No Winner Winner Chicken Dinner ! ");
        System.out.println("Crazy");    }

}
}

---

package GGCGuiLotto;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.JOptionPane;

class GenPLCListener extends GGCGuiLotto implements ActionListener{
public void actionPerformed(ActionEvent event){
        System.out.println("Works");

JOptionPane.showConfirmDialog(null,"Choose Wisely. ","Click If you Trust!",JOptionPane.YES_NO_OPTION);
}
}

Answer 1

Trying to extends GGCGuiLotto isn't going to do what you think it's supposed to, which is give you access to the same instance variables. So get rid of that. Instead you can pass-by-reference , the current instance of GGCGuiLotto to your listener. And have some getters and setters to access the variables you need from the GGCGuiLotto class. What I mean is maybe something like this (not completely sure what you're trying to accomplish, so this is just an example).

public class GenPLCListener implements ActionListener {
    private GGCGuiLotto lotto;

    public GenPLCListener(GGCGuiLotto lotto) {
        this.lotto = lotto;
    }

    @Override
    public void actionPerfomred(ActionEvent e) {
        List<ImageIcon> slotList = lotto.getSlotList();
        Collections.shuffle(slotList);  // shuffle the list
        // do something else if need be.
    }
}

When you create the listener, pass this to it. this being the instance of GGCGuiLotto

---

Few Side Notes

• Swing programs aren't like console programs. You don't want to do everything inside your main method. For starters, the code in your main method, you could put in the constructor instead. Then create an instance of GGCGuiLotto in the main method.

• Swing apps should be run on the Event Dispatch Thread. See Initial Threads

---

EDIT

Maybe a more proper solution to your problem would be to have an interface with the pullSlot method that you can override in the GGCGuiLotto class and just pass the interface to the listener and call the pullSlot method inf your actionPerformed . Something like this

public interface PullInterface {
    public void pullSlot();
}

public class GGCGuiLotto implements PullInterface {
    ArrayList<ImageIcon> slotList = new ArrayList<>();  // global scope.
    JLabel aReel1lbl = new JLabel();
    JLabel bReel2lbl = new JLabel();
    JLabel cReel3lbl = new JLabel();
    Random rand = new Random();

    public GGCGuiLotto() {
        GenPLCListener listener = new GenPLCListener(this);
    }

    @Override
    public void pullSlot() {
        // do what you need to do here to implement a pulling of the lever
        int r1 = rand.nextInt(slotList.size());
        int r2 = rand.nextInt(slotList.size());
        int r3 = rand.nextInt(slotList.size());

        reel1lbl.setIcon(slotList.get(r1));
    }
}

public class GenPLCListener implement ActionListener {
    private PullInterface pull;

    public GenPLCListener(PullInterface pull) {
        this.pull = pull;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        pull.pullSlot();
    }
}