JavaFX drag-and-drop tiles between two GridPane's

Question

I am working on a game as a personal project. It involves tiles that appear both in a rack and on a game board. The rack is a GridPane and the board is a GridPane. I need to be able to drag and drop tiles both within the rack and board, as well as from one to the other.

I have reduced this to a single standalone class with two GridPane's. Each GridPane has one row and 10 columns. Each GridPane initially displays five "tiles". I need to be able to drag and drop any one of the tiles into any available position of either GridPane (i.e. any position that does not already have a tile).

TIA and Happy 4th!

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.RowConstraints;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.stage.Stage;

public class DragAndDropDemoTool extends Application {
    public final double FONT_SIZE = 40;
    public final double NUMBER_OF_COLUMNS_PER_GRID = 10;
    public final double TILE_CURVATURE = 15;
    public final double TILE_SIZE = 50;
    public final double TEXT_POSITION_X = 13;
    public final double TEXT_POSITION_Y = 39;

    @Override
    public void start(Stage stage) throws Exception {
        final VBox rootPane = new VBox();

        rootPane.setPadding(new Insets(20));

        final GridPane topGridPane = new GridPane();
        final GridPane bottomGridPane = new GridPane();

        topGridPane.setHgap(5);
        bottomGridPane.setHgap(5);
        topGridPane.setVgap(10);
        bottomGridPane.setVgap(10);

        // Set equal column widths
        for (int i = 0; i < NUMBER_OF_COLUMNS_PER_GRID; i++) {
            ColumnConstraints columnConstraints = new ColumnConstraints();
            columnConstraints.setPercentWidth(100 / NUMBER_OF_COLUMNS_PER_GRID);
            topGridPane.getColumnConstraints().add(columnConstraints);
            bottomGridPane.getColumnConstraints().add(columnConstraints);
        }

        // Set fixed row height
        RowConstraints rowConstraints = new RowConstraints();
        rowConstraints.setMinHeight(TILE_SIZE + 6);
        topGridPane.getRowConstraints().add(rowConstraints);
        bottomGridPane.getRowConstraints().add(rowConstraints);

        final Canvas canvas0 = createNewTile("0");
        final Canvas canvas1 = createNewTile("1");
        final Canvas canvas2 = createNewTile("2");
        final Canvas canvas3 = createNewTile("3");
        final Canvas canvas4 = createNewTile("4");
        final Canvas canvas5 = createNewTile("5");
        final Canvas canvas6 = createNewTile("6");
        final Canvas canvas7 = createNewTile("7");
        final Canvas canvas8 = createNewTile("8");
        final Canvas canvas9 = createNewTile("9");

        topGridPane.add(canvas1, 1, 0);
        topGridPane.add(canvas3, 3, 0);
        topGridPane.add(canvas5, 5, 0);
        topGridPane.add(canvas7, 7, 0);
        topGridPane.add(canvas9, 9, 0);

        bottomGridPane.add(canvas0, 0, 0);
        bottomGridPane.add(canvas2, 2, 0);
        bottomGridPane.add(canvas4, 4, 0);
        bottomGridPane.add(canvas6, 6, 0);
        bottomGridPane.add(canvas8, 8, 0);

        VBox.setMargin(bottomGridPane, new Insets(20, 0, 0, 0));

        rootPane.getChildren().addAll(topGridPane, bottomGridPane);

        Scene scene = new Scene(rootPane);

        stage.setTitle(this.getClass().getSimpleName());
        stage.setScene(scene);
        stage.show();
    }

    public Canvas createNewTile(final String text) {
        final Canvas canvas = new Canvas(TILE_SIZE, TILE_SIZE);

        final GraphicsContext gc = canvas.getGraphicsContext2D();
        gc.setFill(Color.VIOLET);
        gc.fillRoundRect(0, 0, TILE_SIZE, TILE_SIZE, TILE_CURVATURE, TILE_CURVATURE);
        gc.setFill(Color.PURPLE);

        gc.setFont(Font.font("Arial", FONT_SIZE));
        gc.fillText(text, TEXT_POSITION_X, TEXT_POSITION_Y);

        return canvas;
    }

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