[JAVA][Beginning Java 8 Games Development]

Chapter 16 ■ Collision Detection: Creating SVG Polygons for the Game Actors and Writing Code to Detect Collision
Not only do we need to remove this collided Actor object from the game cast using the CastingDirector class
(object), we also need to remove the ImageView Node from the Scene Graph root as well. Let’s look at how to do that
next, and then we will take a look at how to remove the Actor object from the CURRENT_CAST List after that.
Removing Actors from the Scene Graph: .getChildren().remove()
Now that we have effectively removed the Actor that the InvinciBagel collided with from the cast by adding it to the
REMOVED_ACTORS HashSet object, the next step is to remove it from the JavaFX Scene Graph, which we
are currently using the StackPane UI layout container class for. If you remember earlier in the book, we learned that
the StackPane class can be used as a layer-based layout container, and arranges its contents using a centered XY grid.
We will be learning how to use a Group object (class) as our Scene Graph root later on in the chapter, to implement
the more typical upper-left corner 0,0 XY location indexing scheme and as an optimization, as we are not specifically
using any of the StackPane class properties or methods, and because a Group class is a more basic class that is higher
up in the Node superclass hierarchy. In this way, you will have experienced using both center screen 0,0 location
referencing (StackPane), as well as the traditional upper-left 0,0 screen location referencing (a Group class as a Scene
Graph root).
Removing a Node object from the Scene Graph root is done using a .getChildren().remove() method chain, in
the exact opposite fashion of the .getChildren.add() method call found in the .addGameActorNodes() method. Add a
line of code, and type invinciBagel.root and a period, as shown in Figure 16-35, to open the method helper pop-up.
Figure 16-35. Add a line of code under an .addToRemovedActors() method call and type invinciBagel.root and a
period
Since we are doing this ImageView Node removal from the Bagel.java class, we will use Java dot notation to
preface the root object with the invinciBagel object reference before we add the .getChildren() method call, using
the following invinciBagel.root.getChildren() code shown in Figure 16-35. Double-click on the remove(Object o)
selection and add the object you passed into the .collide() method into the .remove() method, as seen in Figure 16-36.
This will create the final invinciBagel.root.getChildren().remove(object); Java programming statement.
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