drag and drop a node into another node

Question

I'm trying to learn JavaFX by implementing a chess game. My problem is I have no idea how to move a piece by dragging and dropping . In my code I have a 2D array of label in which label contains an ImageView. I want to know how to determine another piece (node) under the dragged piece. Thanks in advance.

Answer 1

Basically you have to use setOnDragDetected() method for the item you want to drag,then use the setOnDragOver() on the target item to determine which TransferMode is accepting and setOnDragDropped() on target method when the drop is done.Finally setOnDragComplete() on the original item to determine that the drag was successful.

1)Link for more info from oracle here

2)A nice example here

3)A second example which is easy to understand:

    /**
 * Demonstrates a drag-and-drop feature.
 */
public class HelloDragAndDrop extends Application {

    @Override
    public void start(Stage stage) {
        stage.setTitle("Hello Drag And Drop");

        Group root = new Group();
        Scene scene = new Scene(root, 400, 200);
        scene.setFill(Color.LIGHTGREEN);

        final Text source = new Text(50, 100, "DRAG ME");
        source.setScaleX(2.0);
        source.setScaleY(2.0);

        final Text target = new Text(250, 100, "DROP HERE");
        target.setScaleX(2.0);
        target.setScaleY(2.0);

        source.setOnDragDetected(event -> {
            /* drag was detected, start drag-and-drop gesture */
            System.out.println("onDragDetected");

            /* allow any transfer mode */
            Dragboard db = source.startDragAndDrop(TransferMode.ANY);

            /* put a string on dragboard */
            ClipboardContent content = new ClipboardContent();
            content.putString(source.getText());
            db.setContent(content);

            event.consume();
        });

        target.setOnDragOver(event -> {
            /* data is dragged over the target */
            System.out.println("onDragOver");

            /*
             * accept it only if it is not dragged from the same node and if it
             * has a string data
             */
            if (event.getGestureSource() != target && event.getDragboard().hasString()) {
                /* allow for both copying and moving, whatever user chooses */
                event.acceptTransferModes(TransferMode.COPY_OR_MOVE);
            }

            event.consume();
        });

        target.setOnDragEntered(event -> {
            /* the drag-and-drop gesture entered the target */
            System.out.println("onDragEntered");
            /* show to the user that it is an actual gesture target */
            if (event.getGestureSource() != target && event.getDragboard().hasString()) {
                target.setFill(Color.GREEN);
            }

            event.consume();
        });

        target.setOnDragExited(event -> {
            /* mouse moved away, remove the graphical cues */
            target.setFill(Color.BLACK);

            event.consume();
        });

        target.setOnDragDropped(event -> {
            /* data dropped */
            System.out.println("onDragDropped");
            /* if there is a string data on dragboard, read it and use it */
            Dragboard db = event.getDragboard();
            boolean success = false;
            if (db.hasString()) {
                target.setText(db.getString());
                success = true;
            }
            /*
             * let the source know whether the string was successfully
             * transferred and used
             */
            event.setDropCompleted(success);

            event.consume();
        });

        source.setOnDragDone(event -> {
            /* the drag-and-drop gesture ended */
            System.out.println("onDragDone");
            /* if the data was successfully moved, clear it */
            if (event.getTransferMode() == TransferMode.MOVE) {
                source.setText("");
            }

            event.consume();
        });

        root.getChildren().add(source);
        root.getChildren().add(target);
        stage.setScene(scene);
        stage.show();
    }

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