Enable labels and textfields based on the selected item in the combo box of another class

Question

I have two separate classes: SubDimensions.java and Subtraction.java.

I wanted to enable some components in the Subtraction class based on the selected item in the combo box of the SubDimensions class. I tried making a switch statement in the SubDimensions class and a boolean function in the Subtraction class but it didn't work. I was wondering what could be the problem.

SubDimensions.java

package gui;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JLabel;
import javax.swing.JComboBox;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.SwingConstants;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JPanel;

public class SubDimensions {

    public JFrame frmSubDimensions;
    public JComboBox comboBoxA;

    /**
     * Launch the application.
     */
    public static void SubDimensions() {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    SubDimensions window = new SubDimensions();
                    window.frmSubDimensions.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public SubDimensions() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    public void initialize() {
        frmSubDimensions = new JFrame();
        frmSubDimensions.setTitle("VECTOR CALCULATOR");
        frmSubDimensions.setBounds(100, 100, 330, 200);
        frmSubDimensions.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmSubDimensions.getContentPane().setLayout(null);

        JLabel lblVectorDimension = new JLabel("Vector dimensions:");
        lblVectorDimension.setHorizontalAlignment(SwingConstants.CENTER);
        lblVectorDimension.setBounds(10, 21, 294, 14);
        frmSubDimensions.getContentPane().add(lblVectorDimension);

        comboBoxA = new JComboBox();
        comboBoxA.setModel(new DefaultComboBoxModel(new String[] {"2x1", "3x1", "4x1", "5x1", "6x1", "7x1", "8x1", "9x1", "10x1"}));
        comboBoxA.setBounds(110, 46, 95, 20);
        frmSubDimensions.getContentPane().add(comboBoxA);

        JButton btnNewButton = new JButton("Okay");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                Subtraction subtraction = new Subtraction();
                subtraction.Subtraction();
                frmSubDimensions.setVisible(false);

                switch(comboBoxA.getSelectedItem().toString()){
                    case "3x1":{
                        subtraction.x3Visibility(true);
                        break;}
                    /*case "4x1":
                        lblX4.setEnabled(true);
                        break;*/
                    default:{
                        subtraction.x3Visibility(false);
                        break;}
                }
            }
        });
        btnNewButton.setBounds(62, 108, 89, 23);
        frmSubDimensions.getContentPane().add(btnNewButton);

        JButton btnCancel = new JButton("Cancel");
        btnCancel.setBounds(167, 108, 89, 23);
        frmSubDimensions.getContentPane().add(btnCancel);
    }
}

Subtraction.java

package gui;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.SwingConstants;
import javax.swing.JTextArea;

public class Subtraction {

        public JFrame frmSubtraction;
        public JTextField textFieldx1;
        public JTextField textFieldx2;
        public JTextField textFieldx3;
        public JTextField textFieldx4;
        public JTextField textFieldx5;
        public JTextField textFieldx6;
        public JTextField textFieldx7;
        public JTextField textFieldx8;
        public JTextField textFieldx9;
        public JTextField textFieldx10;
        public JTextField textFieldy1;
        public JTextField textFieldy2;
        public JTextField textFieldy3;
        public JTextField textFieldy4;
        public JTextField textFieldy5;
        public JTextField textFieldy6;
        public JTextField textFieldy7;
        public JTextField textFieldy8;
        public JTextField textFieldy9;
        public JTextField textFieldy10;
        public JLabel lblX1;
        public JLabel lblX2;
        public JLabel lblX3;
        public JLabel lblX4;
        public JLabel lblX5;
        public JLabel lblX6;
        public JLabel lblX7;
        public JLabel lblX8;
        public JLabel lblX9;
        public JLabel lblX10;
        public JLabel lblY1;
        public JLabel lblY2;
        public JLabel lblY3;
        public JLabel lblY4;
        public JLabel lblY5;
        public JLabel lblY6;
        public JLabel lblY7;
        public JLabel lblY8;
        public JLabel lblY9;
        public JLabel lblY10;

        /**
         * Launch the application.
         */
        public static void Subtraction() {
            EventQueue.invokeLater(new Runnable() {
                public void run() {
                    try {
                        Subtraction window = new Subtraction();
                        window.frmSubtraction.setVisible(true);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            });
        }

        /**
         * Create the application.
         */
        public Subtraction() {
            initialize();
        }

        /**
         * Initialize the contents of the frame.
         */
        public void initialize(){
            SubDimensions subDimensions = new SubDimensions();

            frmSubtraction = new JFrame();
            frmSubtraction.setTitle("VECTOR CALCULATOR");
            frmSubtraction.setBounds(100, 100, 400, 400);
            frmSubtraction.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frmSubtraction.getContentPane().setLayout(null);

            lblX1 = new JLabel("x1");
            lblX1.setBounds(10, 32, 20, 14);
            frmSubtraction.getContentPane().add(lblX1);

            textFieldx1 = new JTextField();
            textFieldx1.setBounds(40, 29, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx1);
            textFieldx1.setColumns(10);

            lblX2 = new JLabel("x2");
            lblX2.setBounds(10, 60, 20, 14);
            frmSubtraction.getContentPane().add(lblX2);

            textFieldx2 = new JTextField();
            textFieldx2.setColumns(10);
            textFieldx2.setBounds(40, 57, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx2);

            lblX3 = new JLabel("x3");
            lblX3.setEnabled(false);
            lblX3.setBounds(10, 88, 20, 14);
            frmSubtraction.getContentPane().add(lblX3);

            textFieldx3 = new JTextField();
            textFieldx3.setEnabled(false);
            textFieldx3.setColumns(10);
            textFieldx3.setBounds(40, 85, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx3);

            lblX4 = new JLabel("x4");
            lblX4.setEnabled(false);
            lblX4.setBounds(10, 116, 20, 14);
            frmSubtraction.getContentPane().add(lblX4);

            textFieldx4 = new JTextField();
            textFieldx4.setEnabled(false);
            textFieldx4.setColumns(10);
            textFieldx4.setBounds(40, 113, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx4);

            lblX5 = new JLabel("x5");
            lblX5.setEnabled(false);
            lblX5.setBounds(10, 144, 20, 14);
            frmSubtraction.getContentPane().add(lblX5);

            textFieldx5 = new JTextField();
            textFieldx5.setEnabled(false);
            textFieldx5.setColumns(10);
            textFieldx5.setBounds(40, 141, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx5);

            lblX6 = new JLabel("x6");
            lblX6.setEnabled(false);
            lblX6.setBounds(10, 172, 20, 14);
            frmSubtraction.getContentPane().add(lblX6);

            textFieldx6 = new JTextField();
            textFieldx6.setEnabled(false);
            textFieldx6.setColumns(10);
            textFieldx6.setBounds(40, 169, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx6);

            lblX7 = new JLabel("x7");
            lblX7.setEnabled(false);
            lblX7.setBounds(10, 200, 20, 14);
            frmSubtraction.getContentPane().add(lblX7);

            textFieldx7 = new JTextField();
            textFieldx7.setEnabled(false);
            textFieldx7.setColumns(10);
            textFieldx7.setBounds(40, 197, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx7);

            lblX8 = new JLabel("x8");
            lblX8.setEnabled(false);
            lblX8.setBounds(10, 228, 20, 14);
            frmSubtraction.getContentPane().add(lblX8);

            textFieldx8 = new JTextField();
            textFieldx8.setEnabled(false);
            textFieldx8.setColumns(10);
            textFieldx8.setBounds(40, 225, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx8);

            lblX9 = new JLabel("x9");
            lblX9.setEnabled(false);
            lblX9.setBounds(10, 256, 20, 14);
            frmSubtraction.getContentPane().add(lblX9);

            textFieldx9 = new JTextField();
            textFieldx9.setEnabled(false);
            textFieldx9.setColumns(10);
            textFieldx9.setBounds(40, 253, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx9);

            lblX10 = new JLabel("x10");
            lblX10.setEnabled(false);
            lblX10.setBounds(10, 281, 30, 14);
            frmSubtraction.getContentPane().add(lblX10);

            textFieldx10 = new JTextField();
            textFieldx10.setEnabled(false);
            textFieldx10.setColumns(10);
            textFieldx10.setBounds(40, 281, 50, 20);
            frmSubtraction.getContentPane().add(textFieldx10);

            lblY1 = new JLabel("y1");
            lblY1.setBounds(126, 32, 20, 14);
            frmSubtraction.getContentPane().add(lblY1);

            textFieldy1 = new JTextField();
            textFieldy1.setColumns(10);
            textFieldy1.setBounds(156, 29, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy1);

            lblY2 = new JLabel("y2");
            lblY2.setBounds(126, 60, 20, 14);
            frmSubtraction.getContentPane().add(lblY2);

            textFieldy2 = new JTextField();
            textFieldy2.setColumns(10);
            textFieldy2.setBounds(156, 57, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy2);

            textFieldy3 = new JTextField();
            textFieldy3.setEnabled(false);
            textFieldy3.setColumns(10);
            textFieldy3.setBounds(156, 85, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy3);

            lblY3 = new JLabel("y3");
            lblY3.setEnabled(false);
            lblY3.setBounds(126, 88, 20, 14);
            frmSubtraction.getContentPane().add(lblY3);

            lblY4 = new JLabel("y4");
            lblY4.setEnabled(false);
            lblY4.setBounds(126, 116, 20, 14);
            frmSubtraction.getContentPane().add(lblY4);

            textFieldy4 = new JTextField();
            textFieldy4.setEnabled(false);
            textFieldy4.setColumns(10);
            textFieldy4.setBounds(156, 113, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy4);

            textFieldy5 = new JTextField();
            textFieldy5.setEnabled(false);
            textFieldy5.setColumns(10);
            textFieldy5.setBounds(156, 141, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy5);

            lblY5 = new JLabel("y5");
            lblY5.setEnabled(false);
            lblY5.setBounds(126, 144, 20, 14);
            frmSubtraction.getContentPane().add(lblY5);

            lblY6 = new JLabel("y6");
            lblY6.setEnabled(false);
            lblY6.setBounds(126, 172, 20, 14);
            frmSubtraction.getContentPane().add(lblY6);

            textFieldy6 = new JTextField();
            textFieldy6.setEnabled(false);
            textFieldy6.setColumns(10);
            textFieldy6.setBounds(156, 169, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy6);

            textFieldy7 = new JTextField();
            textFieldy7.setEnabled(false);
            textFieldy7.setColumns(10);
            textFieldy7.setBounds(156, 197, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy7);

            lblY7 = new JLabel("y7");
            lblY7.setEnabled(false);
            lblY7.setBounds(126, 200, 20, 14);
            frmSubtraction.getContentPane().add(lblY7);

            lblY8 = new JLabel("y8");
            lblY8.setEnabled(false);
            lblY8.setBounds(126, 228, 20, 14);
            frmSubtraction.getContentPane().add(lblY8);

            textFieldy8 = new JTextField();
            textFieldy8.setEnabled(false);
            textFieldy8.setColumns(10);
            textFieldy8.setBounds(156, 225, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy8);

            lblY9 = new JLabel("y9");
            lblY9.setEnabled(false);
            lblY9.setBounds(126, 256, 20, 14);
            frmSubtraction.getContentPane().add(lblY9);

            textFieldy9 = new JTextField();
            textFieldy9.setEnabled(false);
            textFieldy9.setColumns(10);
            textFieldy9.setBounds(156, 253, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy9);

            textFieldy10 = new JTextField();
            textFieldy10.setEnabled(false);
            textFieldy10.setColumns(10);
            textFieldy10.setBounds(156, 281, 50, 20);
            frmSubtraction.getContentPane().add(textFieldy10);

            lblY10 = new JLabel("y10");
            lblY10.setEnabled(false);
            lblY10.setBounds(126, 281, 30, 14);
            frmSubtraction.getContentPane().add(lblY10);

            JLabel lblVectorU = new JLabel("Vector u:");
            lblVectorU.setBounds(10, 11, 80, 14);
            frmSubtraction.getContentPane().add(lblVectorU);

            JLabel lblVectorV = new JLabel("Vector v:");
            lblVectorV.setBounds(126, 11, 80, 14);
            frmSubtraction.getContentPane().add(lblVectorV);

            JTextArea textAreaZ = new JTextArea();
            textAreaZ.setEditable(false);
            textAreaZ.setBounds(251, 27, 123, 274);
            frmSubtraction.getContentPane().add(textAreaZ);

            JButton btnNewButton = new JButton("Calculate");
            btnNewButton.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    int x1 = Integer.parseInt(textFieldx1.getText());
                    int x2 = Integer.parseInt(textFieldx2.getText());
                    int x3 = Integer.parseInt(textFieldx3.getText());
                    int x4 = Integer.parseInt(textFieldx4.getText());
                    int x5 = Integer.parseInt(textFieldx5.getText());
                    int x6 = Integer.parseInt(textFieldx6.getText());
                    int x7 = Integer.parseInt(textFieldx7.getText());
                    int x8 = Integer.parseInt(textFieldx8.getText());
                    int x9 = Integer.parseInt(textFieldx9.getText());
                    int x10 = Integer.parseInt(textFieldx10.getText());

                    int y1 = Integer.parseInt(textFieldy1.getText());
                    int y2 = Integer.parseInt(textFieldy2.getText());
                    int y3 = Integer.parseInt(textFieldy3.getText());
                    int y4 = Integer.parseInt(textFieldy4.getText());
                    int y5 = Integer.parseInt(textFieldy5.getText());
                    int y6 = Integer.parseInt(textFieldy6.getText());
                    int y7 = Integer.parseInt(textFieldy7.getText());
                    int y8 = Integer.parseInt(textFieldy8.getText());
                    int y9 = Integer.parseInt(textFieldy9.getText());
                    int y10 = Integer.parseInt(textFieldy10.getText());

                    int z1 = x1 - y1;
                    int z2 = x2 - y2;
                    int z3 = x3 - y3;
                    int z4 = x4 - y4;
                    int z5 = x5 - y5;
                    int z6 = x6 - y6;
                    int z7 = x7 - y7;
                    int z8 = x8 - y8;
                    int z9 = x9 - y9;
                    int z10 = x10 - y10;

                    textAreaZ.setText(Integer.toString(z1) + "\n" + Integer.toString(z2) + "\n" + Integer.toString(z3) + "\n" + Integer.toString(z4) + "\n" + Integer.toString(z5) + "\n" + Integer.toString(z6) + "\n" + Integer.toString(z7) + "\n" + Integer.toString(z8) + "\n" + Integer.toString(z9) + "\n" + Integer.toString(z10));

                }
            });

            btnNewButton.setBounds(87, 327, 89, 23);
            frmSubtraction.getContentPane().add(btnNewButton);

            JButton btnCancel = new JButton("Cancel");
            btnCancel.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    subDimensions.SubDimensions();
                    frmSubtraction.setVisible(false);
                }
            });
            btnCancel.setBounds(208, 327, 89, 23);
            frmSubtraction.getContentPane().add(btnCancel);

            JLabel lblVectorUv = new JLabel("Vector u+v:");
            lblVectorUv.setBounds(251, 11, 123, 14);
            frmSubtraction.getContentPane().add(lblVectorUv);


    }

    public void x3Visibility (boolean enabled){
        lblX3.setEnabled(enabled);
        textFieldx3.setEnabled(enabled);
        lblY3.setEnabled(enabled);
        textFieldy3.setEnabled(enabled);
    }
    /*public void x4Visibility (boolean visibility){
        lblX4.setEnabled(true);
        textFieldx4.setEnabled(true);
        lblY4.setEnabled(true);
        textFieldy4.setEnabled(true);
    }*/
}

Answer 1

You are not using the parameter enabled in Subtraction.java, change to:

public void x3Visibility (boolean enabled){
lblX3.setEnabled(enabled);
textFieldx3.setEnabled(enabled);
lblY3.setEnabled(enabled);
textFieldy3.setEnabled(enabled);
}

Edit : looks like you lack the fundamental understanding of object-oriented programming (OOP).

When you call

Subtraction subtraction = new Subtraction();
            subtraction.Subtraction();

You created another instance of Subtraction called window:

public static void Subtraction() {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Subtraction window = new Subtraction();
                window.frmSubtraction.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

substraction is not visible while window is. But window is not in the scope of actionPerformed and hence you cannot access it. For now, you can change the actionPerformed to below to resolve your issue temporarily. But I strongly recommend you to: 1) revisit the concept of OOP 2) try to use arrays or collections for your labels and textfields instead of hardcoding them one by one

public void actionPerformed(ActionEvent e) {
            Subtraction subtraction = new Subtraction();
            subtraction.frmSubtraction.setVisible(true);
            frmSubDimensions.setVisible(false);

            switch(comboBoxA.getSelectedItem().toString()){
                case "3x1":{
                    subtraction.x3Visibility(true);
                    break;}
                /*case "4x1":
                    lblX4.setEnabled(true);
                    break;*/
                default:{
                    subtraction.x3Visibility(false);
                    break;}
            }
        }