How to programatically select ComboBox value within Cell Factory?

Question

My TableView uses a custom CellFactory to display a ComboBox in one column, allowing the user to select from available options. Those options are loaded after the TableView is populated (as they can change based on the user's selections elsewhere in the scene).

In the MCVE below, I have two columns for my Item class: Name and Color. Within the Color column, I have the ComboBox which will display the current value of the Item's itemColor property.

You will see that the ComboBox is not populated with a list of values yet and item "Three" has no value selected.

What I need is this:

When the user clicks on the "Load Available Colors" button, the list for the ComboBox is created. The user can now select any of the available colors. However, if there is not already a value for the item's color, I want the first color in the ComboBoxes to be selected automatically; so item "Three" would now show the color "Red" as being selected.

THE MCVE

Item.java:

import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;

public class Item {

    private StringProperty itemName = new SimpleStringProperty();
    private StringProperty itemColor = new SimpleStringProperty();

    public Item(String name, String color) {
        this.itemName.set(name);
        this.itemColor.set(color);
    }

    public String getItemName() {
        return itemName.get();
    }

    public void setItemName(String itemName) {
        this.itemName.set(itemName);
    }

    public StringProperty itemNameProperty() {
        return itemName;
    }

    public String getItemColor() {
        return itemColor.get();
    }

    public void setItemColor(String itemColor) {
        this.itemColor.set(itemColor);
    }

    public StringProperty itemColorProperty() {
        return itemColor;
    }
}

Main.java:

import javafx.application.Application;
import javafx.beans.property.SimpleObjectProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Main extends Application {

    // List of items
    private static ObservableList<Item> listOfItems = FXCollections.observableArrayList();

    // List of available Colors. These will be selectable from the ComboBox
    private static ObservableList<String> availableColors = FXCollections.observableArrayList();

    public static void main(String[] args) {
        launch(args);
    }

    private static void buildSampleData() {

        availableColors.addAll("Red", "Blue", "Green", "Yellow", "Black");
    }

    @Override
    public void start(Stage primaryStage) {

        // Simple Interface
        VBox root = new VBox(10);
        root.setAlignment(Pos.CENTER);
        root.setPadding(new Insets(10));

        // Build a list of sample data. This data is loaded from my data model and passed to the constructor
        // of this editor in my real application.
        listOfItems.addAll(
                new Item("One", "Black"),
                new Item("Two", "Black"),
                new Item("Three", null),
                new Item("Four", "Green"),
                new Item("Five", "Red")
        );

        // TableView to display the list of items
        TableView<Item> tableView = new TableView<>();

        // Create the TableColumn
        TableColumn<Item, String> colName = new TableColumn<>("Name");
        TableColumn<Item, String> colColor = new TableColumn<>("Color");

        // Cell Property Factories
        colName.setCellValueFactory(column -> new SimpleObjectProperty<>(column.getValue().getItemName()));
        colColor.setCellValueFactory(column -> new SimpleObjectProperty<>(column.getValue().getItemColor()));

        // Add ComboBox to the Color column, populated with the list of availableColors
        colColor.setCellFactory(tc -> {
            ComboBox<String> comboBox = new ComboBox<>(availableColors);
            comboBox.setMaxWidth(Double.MAX_VALUE);
            TableCell<Item, String> cell = new TableCell<Item, String>() {
                @Override
                protected void updateItem(String color, boolean empty) {
                    super.updateItem(color, empty);
                    if (empty) {
                        setGraphic(null);
                    } else {
                        setGraphic(comboBox);
                        comboBox.setValue(color);
                    }
                }
            };

            // Set the action of the ComboBox to set the right Value to the ValuePair
            comboBox.setOnAction(event -> {
                listOfItems.get(cell.getIndex()).setItemColor(comboBox.getValue());
            });

            return cell;
        });

        // Add the column to the TableView
        tableView.getColumns().addAll(colName, colColor);
        tableView.setItems(listOfItems);

        // Add button to load the data
        Button btnLoadData = new Button("Load Available Colors");
        btnLoadData.setOnAction(event -> {
            buildSampleData();
        });
        root.getChildren().add(btnLoadData);

        // Add the TableView to the root layout
        root.getChildren().add(tableView);

        Button btnPrintAll = new Button("Print All");
        btnPrintAll.setOnAction(event -> {
            for (Item item : listOfItems) {
                System.out.println(item.getItemName() + " : " + item.getItemColor());
            }
        });
        root.getChildren().add(btnPrintAll);

        // Show the stage
        primaryStage.setScene(new Scene(root));
        primaryStage.setTitle("Sample");
        primaryStage.show();
    }
}

---

Now, with a regular ComboBox, a simple call to comboBox.getSelectionModel().selectFirst() after loading the availableColors would be fine. But since this ComboBox is created within the CellFactory, I am not sure how to update it once the list of colors is populated.

Indidentally, I use this CellFactory implementation instead of a ComboBoxTableCell because I want them to be visible without having to enter edit mode on the TableView.

Answer 1

I actually took kleopatra's advice and updated my data model to include a default value instead. I agree this is cleaner and more appropriate approach.