如何用另一个JList中的数据填充JList

Question

I have a MySQL database which contains data i would like to populate into a JList in my java program. I have two JList, one which is fill with Events Title and the second is to be fill with Guest Name.

What i would like is when the user click on any of the Events Title, the second JList will show all the Guest Name that belong to that Event.

I have already successfully populate the first JList with all the Events Title. What I'm having trouble with is when the user click on the Events Title, the Guests Name will show twice on the second JList. How can i make it to show only once?

Here is what i got so far...

Java Class

private JList getJListEvents() {
    if (jListEvents == null) {
        jListEvents = new JList();
        Border border = BorderFactory.createTitledBorder(BorderFactory.createBevelBorder(1, Color.black, Color.black), "Events", TitledBorder.LEFT, TitledBorder.TOP);
        jListEvents.setBorder(border);
        jListEvents.setModel(new DefaultListModel());
        jListEvents.setBounds(new Rectangle(15, 60, 361, 421));

        Events lEvents = new Events();
        lEvents.loadEvents(jListEvents);

        jListEvents.addListSelectionListener(new ListSelectionListener(){
            public void valueChanged(ListSelectionEvent e){
                EventC eventC = new EventC();
                //eventC.MonitorRegDetailsInfo(jListEvents, jTextFieldEventName, jTextFieldEventVenue, jTextFieldEventDate, jTextFieldEventTime, jTextAreaEventDesc);
                //eventC.MonitorRegPackageInfo(jListEvents, jTextFieldBallroom, jTextFieldBallroomPrice, jTextFieldMeal, jTextFieldMealPrice, jTextFieldEntertainment, jTextFieldEntertainmentPrice);
                eventC.MonitorRegGuest(jListEvents, jListGuest);
            }
        });
    }
    return jListEvents;
}

Controller Class

public void MonitorRegGuest(JList l, JList l2){
    String event = l.getSelectedValue().toString();
    Events retrieveGuest = new Events(event);
    retrieveGuest.loadGuests(l2);
}

Class with all the sql statement

public void loadGuests(JList l){
    ResultSet rs = null;
    ResultSet rs2 = null;
    ResultSet rs3 = null;
    MySQLController db = new MySQLController();
    db.getConnection();

    String sqlQuery = "SELECT MemberID FROM event WHERE EventName = '" + EventName + "'";
    try {
        rs = db.readRequest(sqlQuery);
        while(rs.next()){
            MemberID = rs.getString("MemberID");
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }

    String sqlQuery2 = "SELECT GuestListID FROM guestlist WHERE MemberID = '" + MemberID + "'";
    try {
        rs2 = db.readRequest(sqlQuery2);
        while(rs2.next()){
            GuestListID = rs2.getString("GuestListID");
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }

    String sqlQuery3 = "SELECT Name FROM guestcontact WHERE GuestListID = '" + GuestListID + "'";
    try {
        rs3 = db.readRequest(sqlQuery3);
        while(rs3.next()){
            ((DefaultListModel)l.getModel()).addElement(rs3.getString("Name"));
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }
    db.terminate();
}

Thanks in advance!

Answer 1

Please for the time being forget about the SQL . Then follow the steps below:

1. Start with the example --- the corresponding Java Web Start link .
2. Play with the sample, to see how to add elements to a list.
3. Then all you need to do is grab a reference to the one you want to copy and for each element copy it then add to the 2nd list.
4. Enjoy Java.

EDIT: I am still looking at your code and I am still confused of what is going on (Please consider making a SSCCE ). But let me guess, as something is telling me that when you are calling the ListSelectionListener you are not using getIsValueAdjusting() of the ListSelectionEvent , right? Therefore, this might be as well it, for more read here .

Answer 2

As far as I can see, you aren't clearing the list before populate it, you could try to clear the model first, like:

String sqlQuery3 = "SELECT Name FROM guestcontact WHERE GuestListID = '" + GuestListID + "'";
try {
    rs3 = db.readRequest(sqlQuery3);
    DefaultListModel lm = (DefaultListModel)l;
    lm.clear();
    while(rs3.next()){
        (lm.getModel()).addElement(rs3.getString("Name"));
    }
} catch (SQLException e) {
    e.printStackTrace();
}