DefaultListModel.addElement（）不更新JList

Question

I'm using Firebase with my Java project, I've added a listener to query data then add the elements to DefaultListModel but the JList only removes the old items and doesn't show the new data.
My JList

usersData = new DefaultListModel<>();
JList<String> users = new JList<>(usersData);
users.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
users.setSelectedIndex(0);
users.setVisibleRowCount(5);
JScrollPane fruitListScrollPane = new JScrollPane(users);
add(fruitListScrollPane, BorderLayout.SOUTH);

and my firebase value listener

firebaseRef.addListenerForSingleValueEvent(new ValueEventListener() {

    @Override
    public void onDataChange(DataSnapshot snapshot) {
        // remove all old elements from DefaultListModel
        usersData.removeAllElements();
        // get the data from snapshot
        for (DataSnapshot userSnapshot : snapshot.getChildren()) {
            User user = userSnapshot.getValue(User.class);
            String userInfo = "Username: " + user.getUsername() + " & Password: " + user.getPassword();
            // add the info to the model
            usersData.addElement(userInfo);
            // print the info
            System.out.println(userInfo);
        }
    }

    @Override
    public void onCancelled(FirebaseError error) {
    }
});

Answer 1

is usersData the right scope? I'm thinking it has to do with you updating the information in memory, but not on your UI elements. From the code youve given us, you dont assign or refresh the info in JList, just update the DefaultListModel<>. Try that

Answer 2

The problem is my listner's oonDataChange() runs in a thread so I used this code to do what I needed. I send the data list to this method then start adding them one by one.

public void addElements(final List<String> data) {
    if (SwingUtilities.isEventDispatchThread())
        return;
    SwingUtilities.invokeLater(new Runnable() {

        @Override
        public void run() {
            for (String item : data) {
                usersData.addElement(item);
                System.out.println(item);
            }
        }
    });
}

thanks to Refreshing GUI by another thread in java (swing)