The ListView content is backed up by an ObservableList and any changes to this list are automatically reflected in the ListView, as in the button handler in the next example:

// chaptep10/list/ListViewDemo.java
ObservableList<String> items = FXCollections.observableArrayList(
        "Red", "Blue", "Yellow", "Green");
ListView<String> list = new ListView<>(items);

Button btn = new Button("Add New Item");
btn.setOnAction((e) -> {
    items.add(
            // just a way to generate semirandom new items
            items.get(new Random().nextInt(items.size()))
    );
});