Using JLists In Java Swing

Question

I have to work with JLists for a project and I am stuck trying to do a couple of things. Here are my lists:

JList<String> BooksList = new JList<String>(booksList);
books.add(BooksList, BorderLayout.CENTER);
BooksList.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);


JList cartList = new JList();
cart.add(cartList, BorderLayout.CENTER);
cartList.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);

In The BooksList are the following items:

I Did It Your Way;11.95
The History of Scotland;14.50
Learn Calculus in One Day;29.95
Feel the Stress;18.50
Great Poems;12.95
Europe on a Shoestring;10.95
The Life of Mozart;14.50

1.) Moving Items From BooksList to cartList, specifically I need it to append the newly added items but if I try to add items one at a time then it will replace what is already in cartList with the new item. here is the code I have:

//Adding To Cart
JButton AddToCart = new JButton("Add To Cart");
AddToCart.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        ArrayList<String> selectionList = (ArrayList<String>) BooksList.getSelectedValuesList();
        Object[] selections = selectionList.toArray();
        cartList.setListData(selections);
    }
});
AddToCart.setToolTipText("Alt + A For Auto Add");
AddToCart.setBounds(264, 178, 117, 25);
AddToCart.setMnemonic(KeyEvent.VK_A);
frame.getContentPane().add(AddToCart);

2.) Clearing The Cart List Completely, for some reason nothing happens when this clicked. here is the code:

//This Will Clear The Whole Cart List
JMenuItem Clear = new JMenuItem("Clear                                  Alt + C");
cartMenu.add(Clear);
Clear.setMnemonic(KeyEvent.VK_C);
Clear.addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent arg0) {
        DefaultListModel tempModel = (DefaultListModel)cartList.getModel();
        tempModel.removeAllElements();  
    }

});

3.) Removing Selected Items, same thing as 2 it just doesn't do anything. I have the following code:

//Remove A Selected Item From The List
JMenuItem RemoveSelected = new JMenuItem("Remove Selected             Alt + R");
cartMenu.add(RemoveSelected);
RemoveSelected.setMnemonic(KeyEvent.VK_R);
RemoveSelected.addActionListener(new ActionListener (){
    public void actionPerformed(ActionEvent e) {
        DefaultListModel tempModel = (DefaultListModel)cartList.getModel();
        int selected = cartList.getSelectedIndex();
        if(selected != -1)
        {
            tempModel.remove(selected);
        }
    }
});

Answer 1

When you add to the JList, you want to add it to its ListModel rather than directly:

DefaultListModel tempModel = (DefaultListModel) cartList.getModel();
for (String s: BooksList.getSelectedValuesList())
    tempModel.addElement(s);

I haven't had a chance to test that, but that's the right approach. Currently, you're calling .setListData(), which clears out what's there and replaces it. This will add something to it instead.

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