Thread: Populating second combobox from a combobox help!

Can anyone recommend an Event Listener or some code, that would, when clicking on an item in one jcombobox, populate a different jcombobox.
The event listener/code would have to be in a separate class to the class containing the jcomboboxes, because I have jbuttons that are extending actionlisteners within that class.

Thank you.

I did try both ActionListener and ListSelectionListener, and neither are working. Would it be easier if I uploaded the code I already have?

There are 10 JComboBoxes with five being populated when the program runs. The JComboBoxes work in pairs, so when the user clicks on one of the items in one of populated JComboboxes, the relevant empty Jcombobox will be populated with the subitems of the clicked item.

Below the code shows the many ways I have tried to sort out this problem. Also, I have only been trialling with the first JComboBox, because I just need to repeat the code four more times for the other JComboBoxes with, of course, changing a few of the variables.

Hope this makes sense.

 public void actionPerformed(ActionEvent e) {
        try {
            try {
                if (e.getSource() instanceof JButton) {
                    JButton source = (JButton)e.getSource();
                    if (source == export) {
                        Export exp = new Export();
                        exp.export();
                    }
                    if (source == newT) {
                        NewMenu newM = new NewMenu();
                        newM.newMenu();
                    }
                    if (source == costAll) {
                        costMon.setVisible(true);
                        costTue.setVisible(true);
                        costWed.setVisible(true);
                        costThu.setVisible(true);
                        costFri.setVisible(true);
                        costM.setVisible(true); //If true it shows the textfield
                        costM.setEditable(true);
                        costT.setVisible(true); //If true it shows the textfield
                        costT.setEditable(true);
                        costW.setVisible(true); //If true it shows the textfield
                        costW.setEditable(true);
                        costTh.setVisible(true); //If true it shows the textfield
                        costTh.setEditable(true);
                        costF.setVisible(true); //If true it shows the textfield
                        costF.setEditable(true);
                    }
                    if (source == edit) {
                        Edit edi = new Edit();
                        edi.edit();
                    }
                    if (source == delete) {
                        Delete del = new Delete();
                        del.delete();
                    }
                    if (source == save) {
                        Save sav = new Save();
                        sav.save();
                    }
                }
                if (e.getSource() instanceof JComboBox) {
                    JComboBox jcb = (JComboBox)e.getSource();
                    String choice = (String)jcb.getSelectedItem();
                    if (choice == "Soup") {
                        showSoup();
                    } else if (choice == "Main") {
                        showMain();
                    } else if (choice == "Rushmere") {
                        showRushmere();
                    } else if (choice == "Side") {
                        showSide();
                    } else if (choice == "Bar") {
                        showBar();
                    } else if (choice == "Jacket") {
                        showJacket();
                    } else if (choice == "Dessert") {
                        showDessert();
                    } else {
                        showBread();
                    }
                }
            } catch (IOException es) {}
        } catch (StackOverflowError soe) {}
    }
 
    public void showMain() throws IOException {
        BufferedReader br = new BufferedReader(new FileReader("Courses.txt"));
        BufferedReader brMain = new BufferedReader(new FileReader("Main.txt"));
        String[] course = new String[7];
        String[][] main = new String[7][46];
        for (int a = 0; a < course.length; a++) {
            for (int k = 0; k < 1; k++) {
                main[a][k] = br.readLine(); 
            }
            for (int j = 1; j < main.length; j++) {
                main[a][j] = brMain.readLine();
                mealM.addItem(main[a][j]);
                mealT.addItem(main[a][j]);
                mealW.addItem(main[a][j]);
                mealTh.addItem(main[a][j]);
                mealF.addItem(main[a][j]);
            }
        }
        br.close();
        brMain.close();
    }
 
    //class MondayListener implements ListSelectionListener {
    //    public void valueChanged(ListSelectionEvent lse) {
    //        if (!lse.getValueIsAdjusting() && courseM.getSelectedIndex() != -1) { 
    class MondayListener implements ActionListener {
        public void actionPerformed(ActionEvent lse) {
            System.out.println("BBB");
            try {
                //int index = courseM.getSelectedIndex();
                //System.out.println(index);
                JComboBox cbM = (JComboBox)lse.getSource();
                String choice = (String)cbM.getSelectedItem();
                mealT.setEditable(false);
                mealW.setEditable(false);
                mealTh.setEditable(false);
                mealF.setEditable(false);
                if (choice == "Soup")
                    System.out.println("Soup!");
                if (choice == "Rushmere")
                    showRushmere();
                /*if (index == 0) {
                    showSoup();
                } else if (index == 1) {
                    showMain();
                } else if (index == 2) {
                    showRushmere();
                } else if (index == 3) {
                    showSide();
                } else if (index == 4) {
                    showBar();
                } else if (index == 5) {
                    showJacket();
                } else if (index == 6) {
                    showDessert();
                } else if (index == 7){
                    showBread();
                } */
            } catch (IOException ioe) {}
        }
    }
}

Sure, here's the SSCCE with one pair of JComboboxes:

 
class TimetablePanel extends JPanel implements ActionListener {
 
static JComboBox courseM, mealM;
 
public TimetablePanel() throws IOException {                        //Method to create contents of panel
        courseM = new JComboBox(); //Creates a combo box
        courseM.setEditable(true);
        courseM.setPreferredSize(new Dimension(15, 25));
        courseM.addActionListener(new MondayListener());
        mealM = new JComboBox(); //Creates a combo box
        mealM.setEditable(true);
        mealM.setPreferredSize(new Dimension(15, 25));
 
public void actionPerformed(ActionEvent e) {    //ActionListener for both JButton and JComboBoxes
        try {
            try {
                if (e.getSource() instanceof JButton) {
                    JButton source = (JButton)e.getSource();
                    //Code for the JButtons
                }
                if (e.getSource() instanceof JComboBox) {
                    JComboBox jcb = (JComboBox)e.getSource();
                    String choice = (String)jcb.getSelectedItem();
                    if (choice == "Soup") {
                        showSoup();
                    } else if (choice == "Main") {
                        showMain();
                    }
                }
            } catch (IOException es) {}
        } catch (StackOverflowError soe) {}
    }
 
    public void showMain() throws IOException {                                           //Method to populate second JComboBox
        BufferedReader br = new BufferedReader(new FileReader("Courses.txt"));
        BufferedReader brMain = new BufferedReader(new FileReader("Main.txt"));
        String[] course = new String[7];
        String[][] main = new String[7][46];
        for (int a = 0; a < course.length; a++) {
            for (int k = 0; k < 1; k++) {
                main[a][k] = br.readLine(); 
            }
            for (int j = 1; j < main.length; j++) {
                main[a][j] = brMain.readLine();
                mealM.addItem(main[a][j]);            }
        }
        br.close();
        brMain.close();
    }
 
    class MondayListener implements ActionListener {             //ActionListener for the first JComboBox
        public void actionPerformed(ActionEvent lse) {
            try {
                JComboBox cbM = (JComboBox)lse.getSource();
                String choice = (String)cbM.getSelectedItem();
                if (choice == "Soup")
                    showSoup();
                if (choice == "Main")
                    showMain();
           } catch (IOException ioe) {}
        }
    }
}