ObservableList will not display on TableView because of "Duplicate TableColumns" (JAVAFX)

Question

I'm trying to display data from my ObservableList into a TableView, which I created in SceneBuilder. The TableView contains three TableColumns. I've given them the exact same name as in the FXML-file.

I've imported them into the Controller like you can see down below [1]

And then I'm trying to run my code. I basically have a song. The song consists of a title, artist and album. I want to display it on each column, but it keeps complaining about:

Duplicate TableColumns detected in TableView columns list with titles 'Song title', 'Artist', 'Album'.

And then crashes.

Anybody know what Im doing wrong?

@FXML
private TableView<Song> defaultTableView;

// 1) Song Title

@FXML
private TableColumn songTitleColumn;

// 2) Song artist

@FXML
private TableColumn songArtistColumn;

// 3) Song album
@FXML
private TableColumn songAlbumColumn;


public void initialize(URL location, ResourceBundle resources) {


    Song song1 = new Song("a lot.mp3");

    Song song2 = new Song("Work Out.mp3");

    Song song3 = new Song("Jesus Walks.mp3");

    Playlist myPlaylist = new Playlist("My awesome playlist");

    myPlaylist.addSong(song1);

    myPlaylist.addSong(song2);

    song1.getSongTitleFromDB();

    song1.getSongArtistFromDB();

    song1.getSongAlbumFromDB();

    myPlaylist.displayAllSongs(defaultTableView,songTitleColumn,songArtistColumn,songAlbumColumn);

    ObservableList<Song> songs = FXCollections.observableArrayList();

    songs.add(song1);

    songTitleColumn.setCellFactory(new PropertyValueFactory<Song,String>("songTitle"));

    songArtistColumn.setCellFactory(new PropertyValueFactory<Song, String>("songArtist"));

    songAlbumColumn.setCellFactory(new PropertyValueFactory<Song, String>("songAlbum"));


    defaultTableView.setItems(songs);

    defaultTableView.getColumns().addAll(songTitleColumn,songArtistColumn,songAlbumColumn);

Answer 1

Your fxml file looks something like this:

<TableView fx:id="defaultTableView">
    <columns>
        <TableColumn fx:id="songTitleColumn"/>
        <TableColumn fx:id="songArtistColumn"/>
        <TableColumn fx:id="songAlbumColumn"/>
    </columns>
</TableView>

Since columns is a readonly list property, loading the fxml file results in the columns being added to the TableView. Trying to add them another time to the TableView results in the exception.

You do this in the initialize method:

defaultTableView.getColumns().addAll(songTitleColumn, songArtistColumn, songAlbumColumn);

You need to remove this link or do all of the column creation in the initialize method.