Java FX nested event handler I want to block the parent handler when child handler is called - javafx

Question

I have a fxml Mouse event handler method where every time I click a Pane a pop up dialog box appears on the screen asking for information. When OK is clicked on the dialog, a circle with text is added to a stack pane and the stack pane is then added to the pane where the user clicked.
However I am trying to implement a event handler where I can move the stack pane around by dragging the stack pane with the mouse. My event handler works but every time I finish dragging the stack pane the pop up dialog pops up. I do not want the pop up dialog to pop up when moving the circle how would I change my code to do this is there a way of blocking the pop up handler?
Thank you.
My Handler method:
#FXML
private void handleAddVertex(MouseEvent event) {
boolean okClicked = main.showAddVertexPopUp(this);
if(okClicked) {
String vertexText = "";
if(getSelectedDataChoice().equals("Integer")) {
vertexText = dataModel.getListOfIntVertices().get(dataModel.getListOfIntVertices().size() - 1).toString();
}else if(getSelectedDataChoice().equals("Double")){
vertexText = dataModel.getListOfDoubleVertices().get(dataModel.getListOfDoubleVertices().size() - 1).toString();
}else {
vertexText = dataModel.getListOfStringVertices().get(dataModel.getListOfStringVertices().size() - 1).toString();
}
EventHandler<MouseEvent> circleOnMousePressedEventHandler =
new EventHandler<MouseEvent>() {
#Override
public void handle(MouseEvent t) {
orgSceneX = t.getSceneX();
orgSceneY = t.getSceneY();
orgTranslateX = ((StackPane)(t.getSource())).getTranslateX();
orgTranslateY = ((StackPane)(t.getSource())).getTranslateY();
}
};
EventHandler<MouseEvent> circleOnMouseDraggedEventHandler =
new EventHandler<MouseEvent>() {
#Override
public void handle(MouseEvent t) {
double offsetX = t.getSceneX() - orgSceneX;
double offsetY = t.getSceneY() - orgSceneY;
double newTranslateX = orgTranslateX + offsetX;
double newTranslateY = orgTranslateY + offsetY;
((StackPane)(t.getSource())).setTranslateX(newTranslateX);
((StackPane)(t.getSource())).setTranslateY(newTranslateY);
}
};
double x = event.getX();
double y = event.getY();
Circle vertex = new Circle(x, y, 20, Color.WHITE);
vertex.setStroke(Color.BLACK);
Text text = new Text (vertexText);
StackPane stack = new StackPane();
stack.getChildren().addAll(vertex, text);
stack.setLayoutX(x);
stack.setLayoutY(y);
stack.setOnMousePressed(circleOnMousePressedEventHandler);
stack.setOnMouseDragged(circleOnMouseDraggedEventHandler);
centerPane.getChildren().add(stack);
}
}

Answer 1

To stop an Event from propagating you use Event.consume().
Marks this Event as consumed. This stops its further propagation.
From your description, it appears handleAddVertex is a MOUSE_CLICKED handler. You'll have to add another EventHandler to the newly created StackPane that consumes MOUSE_CLICKED events.
stack.setOnMouseClicked(Event::consume);
This will stop the MOUSE_CLICKED event from bubbling up to the Node which has the handleAddVertex handler.
For more information on event processing in JavaFX, see JavaFX: Handling Events.
Here's a small example where you can see the difference between consuming and not consuming the event:
import java.util.function.Predicate;
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Point2D;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.ButtonType;
import javafx.scene.control.CheckBox;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Border;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.BorderStroke;
import javafx.scene.layout.BorderStrokeStyle;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
public class Main extends Application {
private CheckBox consumeClickEventsCheckBox;
#Override
public void start(Stage primaryStage) throws Exception {
consumeClickEventsCheckBox = new CheckBox("Consume click events");
consumeClickEventsCheckBox.setSelected(true);
HBox top = new HBox(consumeClickEventsCheckBox);
top.setPadding(new Insets(10));
top.setAlignment(Pos.CENTER);
Pane center = new Pane();
center.setBorder(new Border(new BorderStroke(Color.BLACK, BorderStrokeStyle.SOLID, null, null)));
center.setOnMouseClicked(this::handleAddCircle);
Rectangle clip = new Rectangle();
clip.widthProperty().bind(center.widthProperty());
clip.heightProperty().bind(center.heightProperty());
center.setClip(clip);
BorderPane root = new BorderPane(center);
root.setTop(top);
Scene scene = new Scene(root, 600, 400);
primaryStage.setScene(scene);
primaryStage.show();
}
private void handleAddCircle(MouseEvent event) {
event.consume();
Alert confirm = new Alert(AlertType.CONFIRMATION);
confirm.initOwner(((Node) event.getSource()).getScene().getWindow());
confirm.setHeaderText(null);
confirm.setContentText("Do you want to add a circle here?");
if (confirm.showAndWait().filter(Predicate.isEqual(ButtonType.OK)).isPresent()) {
Circle circle = new Circle(event.getX(), event.getY(), 25);
circle.setOnMousePressed(this::handleCirclePressed);
circle.setOnMouseDragged(this::handleCircleDragged);
circle.setOnMouseClicked(this::handleCircleClicked);
((Pane) event.getSource()).getChildren().add(circle);
}
}
private Point2D origin;
private void handleCirclePressed(MouseEvent event) {
event.consume();
origin = new Point2D(event.getX(), event.getY());
}
private void handleCircleDragged(MouseEvent event) {
event.consume();
Circle circle = (Circle) event.getSource();
circle.setTranslateX(circle.getTranslateX() + event.getX() - origin.getX());
circle.setTranslateY(circle.getTranslateY() + event.getY() - origin.getY());
}
/*
* Will consume the MOUSE_CLICKED event only if the CheckBox is selected. You can test
* the behavior of consuming the event by toggling the CheckBox.
*/
private void handleCircleClicked(MouseEvent event) {
if (consumeClickEventsCheckBox.isSelected()) {
event.consume();
}
}
}