How to drag an undecorated window (stage) of JavaFX

Question

I have this undecorated window:

public static void initStartPage(final Stage primaryStage) {

        final Stage startPage = new Stage();
        startPage.initStyle(StageStyle.UNDECORATED);
        //startPage.initOwner(primaryStage);
        //startPage.toFront();
        Scene scene = new Scene(agentsPanel(), 900, 500);
        startPage.setScene(scene);
        startPage.show();

    }

I would like to know how I can make it a draggable undecorated window? I want to change its position when the user selects the window with the right mouse button and then move the mouse while keeping the mouse button pressed down.

P.S. I tested this solution, but it's not working:

private static FlowPane flow;
    private static BorderPane bpi;

    public static void initStartPage(final Stage primaryStage) {

        final Stage startPage = new Stage();
        startPage.initStyle(StageStyle.UNDECORATED);
        startPage.initOwner(primaryStage);
        //startPage.toFront();
        Scene scene = new Scene(agentsPanel(primaryStage), 900, 500);
        startPage.setScene(scene);
        startPage.show();

    }

    private static double xOffset = 0;
    private static double yOffset = 0;

    public static BorderPane agentsPanel(final Stage primaryStage) {

        BorderPane bp = new BorderPane();
        bp.setPrefSize(900, 500);
        bp.setMaxSize(900, 500);

        HBox thb = new HBox(10); // Set spacing between each child into the HBox
        thb.setPadding(new Insets(15, 15, 15, 15));


        HBox bhb = new HBox(10); // Set spacing between each child into the HBox
        bhb.setPadding(new Insets(15, 15, 15, 15));

        bp.setTop(thb);
        bp.setBottom(bhb);
        bp.setCenter(navigationPanel());


        bp.setOnMousePressed(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                xOffset = event.getSceneX();
                yOffset = event.getSceneY();
            }
        });
        bp.setOnMouseDragged(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                primaryStage.setX(event.getScreenX() - xOffset);
                primaryStage.setY(event.getScreenY() - yOffset);
            }
        });

        return bp;

    }

Answer 1

The @Eeliyaanswer working well. However, code will shorter if using the below code because we don't need to declare variables.

We need to setOnMouseDragged again and again whenever setOnMouseDragged fired but I think it's not causing the problem.

bp.setOnMousePressed(pressEvent -> {
    bp.setOnMouseDragged(dragEvent -> {
        primaryStage.setX(dragEvent.getScreenX() - pressEvent.getSceneX());
        primaryStage.setY(dragEvent.getScreenY() - pressEvent.getSceneY());
    });
});

Hope it helps

Answer 2

you can use this, works for a stage as well as an Alert (basically another stage but for pup po messages). the node is the main node of that stage

//Make a Stage Draggable
public void DraggableStage(Node node, Stage stage, Alert alert ) {
    double[] xOffset = {0}, yOffset = {0};
    node.setOnMousePressed(event -> {
        if (stage != null && alert == null){
            xOffset[0] = stage.getX() - event.getScreenX();
            yOffset[0] = stage.getY() - event.getScreenY();
        } else if(stage == null && alert != null){
            xOffset[0] = alert.getX() - event.getScreenX();
            yOffset[0] = alert.getY() - event.getScreenY();
        }
    });

    node.setOnMouseDragged(event -> {
        if (stage != null && alert == null){
            stage.setX(event.getScreenX() + xOffset[0]);
            stage.setY(event.getScreenY() + yOffset[0]);
        } else if(stage == null && alert != null){
            alert.setX(event.getScreenX() + xOffset[0]);
            alert.setY(event.getScreenY() + yOffset[0]);
        }
    });
}

Answer 3

Just change your setOnMousePressed method to this:

bp.setOnMousePressed(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                xOffset = primaryStage.getX() - event.getScreenX();
                yOffset = primaryStage.getY() - event.getScreenY();
            }
        });

and your setOnMouseDragged to this:

bp.setOnMouseDragged(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                primaryStage.setX(event.getScreenX() + xOffset);
                primaryStage.setY(event.getScreenY() + yOffset);
            }
        });