Issues Getting Button to Change Label Text

Question

Recently I've been trying to make a program that takes in a double in the form of a string. It then parses that to a double which goes to another class to be divided to a quarter or a half and then returns that output to a label.

I've been having an issue where when I click a button to actually submit what is inside the text field, the label doesn't change.

I've tried a lot of trial and error and I know I can change the text after doing new JLabel("test") for example. However, there seems to be an issue with my action listener for when the button is pushed. I can't tell if it's not seeing the button as being pushed.

NOTE: I am new to awt event things and swing as a whole, I usually operate just using the output terminal of visual studio code where it's just text and no graphics.

import javax.swing.*;
import java.awt.event.*;
import java.awt.Font;
import java.awt.Dimension;

public class MoneySorterRunner {
    
    private  MoneySorter sorter = new MoneySorter();

    private String input = "0";
    private double money = Double.parseDouble(input);
    private static JTextField typeHere = new JTextField();


///labels num1-3 are the labels being changed
    private static JLabel num1 = new JLabel(new MoneySorterRunner().sorter.divQuarter(new MoneySorterRunner().money));
    private static JLabel num2 = new JLabel(new MoneySorterRunner().sorter.divQuarter(new MoneySorterRunner().money));
    private static JLabel num3 = new JLabel(new MoneySorterRunner().sorter.divHalf(new MoneySorterRunner().money));

    public static void main(String args[]) {
        JFrame frame = new JFrame("Money Calculator - v0.1a");
        JPanel panel = new JPanel();
        JButton doThing = new JButton("Do a Thing");
        doThing.setActionCommand("Do a Thing");
        frame.add(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 250);
        frame.setLocation(200, 200);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        panel.setLayout(null);
        frame.setVisible(true);
        JLabel item1 = new JLabel("test");
        JLabel item2 = new JLabel("test");
        JLabel item3 = new JLabel("test");
        item1.setFont(new Font("Arial", Font.PLAIN, 30));
        item2.setFont(new Font("Arial", Font.PLAIN, 30));
        item3.setFont(new Font("Arial", Font.PLAIN, 30));
        num1.setFont(new Font("Arial", Font.PLAIN, 25));
        num2.setFont(new Font("Arial", Font.PLAIN, 25));
        num3.setFont(new Font("Arial", Font.PLAIN, 25));
        Dimension size1 = item1.getPreferredSize();
        Dimension size2 = item2.getPreferredSize();
        Dimension size3 = item3.getPreferredSize();
        panel.add(item1);
        panel.add(item2);
        panel.add(item3);
        panel.add(num1);
        panel.add(num2);
        panel.add(num3);
        panel.add(doThing);
        panel.add(typeHere);
        item1.setBounds(10, 10, size1.width + 3, size1.height);
        item2.setBounds(190, 10, size2.width + 3, size2.height);
        item3.setBounds(325, 10, size3.width + 3, size3.height);
        num1.setBounds(50, 50, 50, 25);
        num2.setBounds(200, 50, 50, 25);
        num3.setBounds(350, 50, 50, 25);
        doThing.setBounds(250, 150, 100, 25);
        typeHere.setBounds(100, 150, 150, 25);

    }

    public void actionPerformed(ActionEvent event){
        String check = event.getActionCommand();
        if(check.equals("Do a Thing")){
            input = typeHere.getText();
        }
        if(input != "0"){
            num1.setText(sorter.divQuarter(money));
            num2.setText(sorter.divQuarter(money));
            num3.setText(sorter.divHalf(money));
        }
    }

}

For those who wanted the MoneySorter.java:

    public MoneySorter(){

    }

    public String divQuarter(double moneyIn){
        String answer = Double.toString(moneyIn);
        return answer;
    }

    public String divHalf(double moneyIn){
        String answer = Double.toString(moneyIn);
        return answer;
    }
}

Answer 1

I understand that your program is supposed to do the following.

User enters an amount of money in a JTextField and when she clicks on a JButton the JLabels show the entered amount in dollars, half-dollars and quarters (as per U.S. currency). My answer, below, is based on this understanding.

I don't know if making all the variables static is good or bad but I never use static class member variables in my Swing programs.

Here is my analysis of your code.

private double money = Double.parseDouble(input);

This line of code will be executed precisely once, when you launch class MoneySorterRunner. You want to do this every time the JButton is clicked, hence parsing the text entered into the JTextField should be performed in the actionPerformed method.

JPanel panel = new JPanel();
panel.setLayout(null);

It is almost never needed to set the layout manager to null. You can almost always find an appropriate layout manager or you can place one JPanel within another and use different layout managers for each JPanel in order to get the desired placement of components within the Swing application window.

JButton doThing = new JButton("Do a Thing");
doThing.setActionCommand("Do a Thing");

By default, the text of a JButton is also its action command so no need to explicitly set it.

frame.setLocation(200, 200);
frame.setLocationRelativeTo(null);

These are two different ways to set the location of the JFrame and they do not complement each other. Use one or the other, but not both.

frame.setVisible(true);

Only after you have created all the [GUI] components and added them to the JFrame should you make the JFrame visible. So this should be the last line of the code that creates your GUI.

doThing.setBounds(250, 150, 100, 25);

If you use a layout manager, you never need to call method setBounds.

if(input != "0"){

This is not the way to compare strings. Use method equals as you have done here

if(check.equals("Do a Thing")){

Here is my rewrite of your application. Note that since I could not find the code for class MoneySorter, in your question, I just created my own version of that class. The point is to show how to change the text of the JLabel after clicking on the JButton and not how to create the actual text to display.

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class MoneySorterRunner implements ActionListener {
    private MoneySorter sorter = new MoneySorter();
    private JTextField typeHere = new JTextField();

    private JLabel num1;
    private JLabel num2;
    private JLabel num3;

    private void createAndShowGui() {
        JFrame frame = new JFrame("Money Calculator - v0.1a");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.add(createLabels(), BorderLayout.PAGE_START);
        frame.add(createForm(), BorderLayout.CENTER);
        frame.setSize(550, 250);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private JPanel createForm() {
        JPanel panel = new JPanel(new FlowLayout(FlowLayout.CENTER, 10, 0));
        panel.setBorder(BorderFactory.createEmptyBorder(20, 0, 0, 0));
        typeHere = new JTextField(10);
        panel.add(typeHere);
        JButton doThing = new JButton("Do a Thing");
        doThing.addActionListener(this);
        panel.add(doThing);
        return panel;
    }

    private static JLabel createLabel(String text) {
        JLabel label = new JLabel(text);
        label.setFont(new Font("Arial", Font.PLAIN, 25));
        return label;
    }

    private JPanel createLabels() {
        JPanel panel = new JPanel(new GridLayout());
        num1 = createLabel("num1");
        panel.add(num1);
        num2 = createLabel("num2");
        panel.add(num2);
        num3 = createLabel("num3");
        panel.add(num3);
        return panel;
    }

    public static void main(String args[]) {
        new MoneySorterRunner().createAndShowGui();
    }

    public void actionPerformed(ActionEvent event){
        String check = event.getActionCommand();
        if(check.equals("Do a Thing")){
            String text = typeHere.getText();
            if (!text.isEmpty()) {
                double money = Double.parseDouble(text);
                num1.setText(sorter.divQuarter(money));
                num2.setText(sorter.divQuarter(money));
                num3.setText(sorter.divHalf(money));
            }
        }
    }
}

class MoneySorter {

    public String divQuarter(double money) {
        return "divQuarter(" + money + ")";
    }

    public String divHalf(double money) {
        return "divHalf(" + money + ")";
    }
}

This is how your GUI looked when I ran your original code (as posted in your question).

This is how the GUI looks when running the code in this answer.

After launching

After entering a value and clicking the JButton

Answer 2

It looks like you forgot to set the ActionListener. You should also change your method to another name, because your method has the same name as the actionPerformed of the ActionListener.

doThing.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                new MoneySorterRunner().actionPerformedMethod(e);
            }
        });

Answer 3

You forgot to add the ActionListener. In order to fix this, you need to do two things:

1. Add this statement to your code, preferably near where you create the button (so that it is easier to keep track). -

doThing.addActionListener(this);

2. When you write "public class", you also need this keyword: implements ActionListener - meaning your class (basically the first line) should look like:

public class MoneySorterRunner implements ActionListener

And that should make it work.