Trying to implement JComboBox into program - Java

Question

This is my first post!

I'm trying to implement the combo box made in the TutCombo program into the ExamGradesGUI + ExamGrades one. As you can see in the TutCombo program, there is the 'String subjectUnitTxt'. Ideally, I would like this to replace the 'subjectUnitTxt' in the ExamGradesGUI program, but having the functionality of the combo box and being able to be saved to the file along with firstName, lastName and examMark. If someone could tell me how to do this, that would be great. Sorry if I have added too much code. Thanks

Answer 1

I got this to work by making some minor changes in your code (see attached code). Search for "unitCombo".

import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class ExamGradesGUI {
    public static void main(String[] args) {
        new ExamGradesGUI();
    }

    String[] firstName = new String[20];
    String[] lastName = new String[20];
    String[] subjectUnit = new String[20];
    double[] examMark = new double[20];
    private JLabel firstNameLbl, lastNameLbl, unitLbl, markLbl;
    private JTextField firstNameTxt, lastNameTxt, subjectUnitTxt, examMarkTxt;
    private JComboBox<String> unitCombo;
    private JButton btnClear, btnSave, btnOpen, btnExit;
    private JPanel panel;
    private JFrame frame;

    public ExamGradesGUI(){
        buildFrame();
        buildFields();
        buildButtons();
        frame.setVisible(true);
        frame.add(panel);
    }

    public void buildFrame(){
        frame = new JFrame("GradeEnter");
        frame.setSize(650,450);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        panel = new JPanel();
        panel.setLayout(null);
        panel.setBackground(Color.white);
    }

    public void buildFields(){

        // Labels, User Input + Location

        firstNameTxt = new JTextField(10);
        firstNameTxt.setBounds(180, 80, 150, 20);
        panel.add(firstNameTxt);

        String str = firstNameTxt.getText(); 
        if(str.matches("[-a-zA-Z]*"))
        {
        }
        else
        {
            JOptionPane.showMessageDialog(null, "Please enter amount donating");
        }

        lastNameTxt = new JTextField(10);
        lastNameTxt.setBounds(180, 110, 150, 20);
        panel.add(lastNameTxt);

        subjectUnitTxt = new JTextField(10);
        String[] courses = {"Computing","Forensic","Business"};
        unitCombo = new JComboBox<String>(courses);
        //subjectUnitTxt.setBounds(180, 140, 150, 20);
        //panel.add(subjectUnitTxt);
        unitCombo.setBounds(180, 140, 150, 20);
        panel.add(unitCombo);

        // IF HAVE TIME: Turn Combo Box into GUI - Refer to testgui.java

        examMarkTxt = new JTextField(10);
        examMarkTxt.setBounds(180, 170, 150, 20);
        panel.add(examMarkTxt);

        firstNameLbl = new JLabel("First Name:");
        firstNameLbl.setBounds(70, 80, 100, 20);
        panel.add (firstNameLbl);

        lastNameLbl = new JLabel("Last Name:");
        lastNameLbl.setBounds(70, 110, 100, 20);
        panel.add (lastNameLbl);

        unitLbl = new JLabel("Unit:");
        unitLbl.setBounds(70, 140, 100, 20);
        panel.add (unitLbl);

        markLbl = new JLabel("Mark:");
        markLbl.setBounds(70, 170, 100, 20);
        panel.add (markLbl);

    }

    public void buildButtons() {
        btnClear = new JButton ("Reset Fields");
        btnClear.setBounds(55, 220, 110, 20);
        btnClear.addActionListener(new ClearButtonListener());
        panel.add (btnClear);

        btnSave = new JButton ("Save");
        btnSave.setBounds(155, 220, 70, 20);
        btnSave.addActionListener(new SaveButton());
        panel.add (btnSave);

        btnOpen = new JButton ("Open 'GradeEnter.txt' ");
        btnOpen.setBounds(90, 250, 200, 20);
        btnOpen.addActionListener(new OpenButton());
        panel.add (btnOpen);


        btnExit = new JButton ("Exit");
        btnExit.setBounds(255, 220, 70, 20);
        btnExit.addActionListener(new ExitButton());
        panel.add (btnExit);

    }
    public void setText() {
        firstNameTxt.setText("");
        lastNameTxt.setText("");
        subjectUnitTxt.setText("");
        examMarkTxt.setText("");
    }

    public void getText() {
        int i = 0;
        i++;
        firstName[i] = firstNameTxt.getText();
        lastName[i] = lastNameTxt.getText();
        subjectUnit[i] = unitCombo.getItemAt(unitCombo.getSelectedIndex());
        examMark[i] = Double.parseDouble(examMarkTxt.getText());
    }
    private class ClearButtonListener implements ActionListener {

        public void actionPerformed (ActionEvent e) {
            setText();
        }
    }

    private class SaveButton implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            getText();
            setText();

            ExamGrades save = new ExamGrades();
            save.fileOpen();
            save.addRecords(firstName, lastName, subjectUnit, examMark);
            JOptionPane.showMessageDialog(null, "Entry Saved!");
            save.fileClose();

        }
    }
    private class OpenButton implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            try { 
                JOptionPane.showMessageDialog(null, "'GradeEnter.txt' opening in Java!"); 
                Thread.sleep(2); // Adds a 2 second delay so user can read dialog message
                Runtime.getRuntime().exec("eclipse GradeEnter.txt" );


            } catch (Exception NoFileFound) { 
                System.out.println("Couldn't open or find the file.");
            } 
        }
    }

    class ExitButton implements ActionListener{
        public void actionPerformed(ActionEvent e) {
            int n = JOptionPane.showConfirmDialog(frame, 
                    "Are you sure you want to exit?", 
                    "Exit?", 
                    JOptionPane.YES_NO_OPTION);
            if(n == JOptionPane.YES_OPTION){
                System.exit(0);
            }
        }
    }

}