ListModel Example

• We'll start with what we already have in JListObject.
• But, we're going to replace the Array with a DefaultListModel.
• We will add this to the JList object via the setModel(ListModel m) method.
• Normally, we could just send the model into the constructor for the JList.  But, that is locked down since we used the GUI editor.  So, we have to use the setModel(ListModel m) method instead.  This works just as well.
• To prove that we can dynamically add Building objects, let's put an Add button on the screen as well.
• The ActionListener for this button will prompt the user with two pop-up boxes for informaiton to create the Building object.
• Next, it will create a Building object with that data.
• And finally, it will add that Building object to the model.  You will see that the JList updates itself.
• We could also have a 'remove' button to prove that removing objects works, but I'll leave that to you in open lab time.
• First, the new pop up:

• Next, the result.  Note the new building, Crosley, has been added to the list.

• I copied JListObject to JListObjectModel.  Changed text is in green.
• Note that many of the changes were made automatically because I used Forte's GUI editor.

import javax.swing.*;

/**
 *
 * @author  default
 */
public class JListObjectModel extends javax.swing.JFrame {
 
    DefaultListModel buildingModel;
 
    /** Creates new form JListString */
    public JListObjectModel() {
        initComponents();

 
        // We don't need the Array any more.
        // Let's just use the DefaultListModel instead.
 
        buildingModel = new DefaultListModel();
 
        // Build the objects on the fly and add them to the model.
        buildingModel.addElement(new Building("Sander", "CECE Computer Labs"));
        buildingModel.addElement(new Building("French", "CECE Administration"));
        buildingModel.addElement(new Building("Langsam", "Library"));
        buildingModel.addElement(new Building("Lindner", "College of Business Administration"));
        buildingModel.addElement(new Building("Tangeman", "Old University Center"));
        buildingModel.addElement(new Building("Tent City", "New University Center"));
        buildingModel.addElement(new Building("Shoemaker", "Arena"));
        buildingModel.addElement(new Building("Edwards", "Administration Center"));
 
        // Change setListData(buildings) to setModel(buildingModel)
        lstBuildings.setModel(buildingModel);
    }
 
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    private void initComponents() {
        scrBuildingList = new javax.swing.JScrollPane();
        lstBuildings = new javax.swing.JList();
        pnlButtons = new javax.swing.JPanel();
        btnShow = new javax.swing.JButton();
        btnAdd = new javax.swing.JButton();
        lblTitle = new javax.swing.JLabel();

        addWindowListener(new java.awt.event.WindowAdapter() {
            public void windowClosing(java.awt.event.WindowEvent evt) {
                exitForm(evt);
            }
        });

        scrBuildingList.setViewportView(lstBuildings);

        getContentPane().add(scrBuildingList, java.awt.BorderLayout.CENTER);

        btnShow.setText("Show");
        btnShow.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnShowActionPerformed(evt);
            }
        });

        pnlButtons.add(btnShow);

        btnAdd.setText("Add Building");
        btnAdd.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnAddActionPerformed(evt);
            }
        });

        pnlButtons.add(btnAdd);

        getContentPane().add(pnlButtons, java.awt.BorderLayout.SOUTH);

        lblTitle.setText("Where have you been?");
        getContentPane().add(lblTitle, java.awt.BorderLayout.NORTH);

        pack();
    }

    private void btnAddActionPerformed(java.awt.event.ActionEvent evt) {
        // Prompt the user for building name, function
        String buildingName = JOptionPane.showInputDialog(this, "Enter the building name:");
        String buildingFunction = JOptionPane.showInputDialog(this, "Enter the building function:");
 
        // Create a new building object based on the user's input.
        Building building = new Building(buildingName, buildingFunction);
 
        // Add this building to the model.
        buildingModel.addElement(building);
 
    }
 
    private void btnShowActionPerformed(java.awt.event.ActionEvent evt) {
 
        //  get the selected buildings from the JList.
        Object[] selectedBuildings = lstBuildings.getSelectedValues();
 
        // Create a String that we will use to display an informative message to the user.
        String message = "Today you have been to the ";
 
        for (int i = 0; i < selectedBuildings.length; i++){
            if (i > 0) { message += ", "; }
 
            // Eliminate the for loop and if test.
            // Just get the Building object directly from the JList.
            Building building = (Building) selectedBuildings[i];
            message += building.getFunction();
        }
 
        JOptionPane.showMessageDialog(this, message, "Buildings Visited", JOptionPane.INFORMATION_MESSAGE);
 
    }
 
    /** Exit the Application */
    private void exitForm(java.awt.event.WindowEvent evt) {
        System.exit(0);
    }
 
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        new JListObjectModel().show();
    }
 
 
    // Variables declaration - do not modify
    private javax.swing.JLabel lblTitle;
    private javax.swing.JList lstBuildings;
    private javax.swing.JPanel pnlButtons;
    private javax.swing.JButton btnAdd;
    private javax.swing.JScrollPane scrBuildingList;
    private javax.swing.JButton btnShow;
    // End of variables declaration
 
}

Created by:  Brandan Jones December 17, 2001