Question

I’m trying to set up a character manager for a LARP game. In the game a character could have more than one role (1 or 2). I want to generate the character using two comboboxes, both drawing from the same enum called Role. That in itself is easy:

    JComboBox roleFirstComboBox = new JComboBox(IPlayerCharacter.Role.values());
    JComboBox roleSeondComboBox = new JComboBox(IPlayerCharacter.Role.values());

Except if say our roles are: Coder, Programmer, SysAdmin, Nerdfighter you can be a Coder/Coder. So the second box needs to exclude whatever is selected in the first box.

One thought I had was making a function to pass the enums to a List of some sort and then when one JComboBox is picked, it uses one of the standard container methods to find the asynchronous union(?) everything in Box2 that isn’t in Box1. This seems horrible. I know the solution uses a JComboBoxModel but how to adapt this to my enums, I don’t know.

What is the best way to get this kind of functionality?

Edit:

Here is the code I’m using currently, it just lives inside my pane, so I don’t think it needs anymore context. Let me know otherwise, if need be.

Creating the comboBoxes

JComboBox roleFirstComboBox = null;
JComboBox roleSecondComboBox = null;
...
roleFirstComboBox = new JComboBox(IPlayerCharacter.Role.values());
roleSecondComboBox = new JComboBox(IPlayerCharacter.Role.values());

Adding an actionListener:

roleFirstComboBox.addActionListener(new ActionListener() {

    @Override
    public void actionPerformed(ActionEvent arg0) {
        roleSecondComboBox.removeAll();
        roleSecondComboBox.addItem(null);
        for (Role role : IPlayerCharacter.Role.values()) {
            if (role != roleFirstComboBox.getSelectedItem()) {
                    roleSecondComboBox.addItem(role);
            } 
        }
    }
});
roleFirstComboBox.setSelectedIndex(0);

Adding it to the groupLayout:

.addComponent(roleFirstComboBox)
.addComponent(roleSecondComboBox))

The final look, and bug:

Does this help?

Answer 1

Add an ActionListener to the first combo box. When the action is triggered, reset the model on the second combo box to the full list of roles, and then use removeItem(Object) to remove the already selected role from the second box. Alternately, empty the model and re-add all items except for the selected one:

private enum Roles {CODER, MANAGER, USER}

JComboBox box1 = new JComboBox(Roles.values());
JComboBox box2 = new JComboBox();
public RoleSelection() {
    box1.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            box2.removeAllItems();
            box2.addItem(null); // For those with only one role
            for (Roles role : Roles.values()) {
                if (role != box1.getSelectedItem()) {
                    box2.addItem(role);
                }
            }
        }
    });
    // Trigger a selection even to update the second box
    box1.setSelectedIndex(0);

    add(box1, BorderLayout.NORTH);
    add(box2, BorderLayout.SOUTH);
    pack();
    setDefaultCloseOperation(EXIT_ON_CLOSE);
}

public static void main(String[] args) {
    new RoleSelection().setVisible(true);
}