How to have multiple instances on the screen of th

Question

I'm quite new in programming and especially with javafx. I'm writing a game and i'm trying to visualize at the same time more instances of the same sprite ( a kind of bullet). It translates and rotates. In my attempts program doesn't work or normally when press 'fire', bullet run but when press 'fire' more times, every time the 'old' bullet' disappear and another bullet starts. Only 1 bullet on the screen at the same time. What have i to do to have more bullets on the screen, exactly one bullet for every time 'fire' is pressed? Thank you in advance!

Answer 1

You are probably trying to add the same node more than once to the scene graph.

From the JavaFX Node documentation:

A node may occur at most once anywhere in the scene graph. Specifically, a node must appear no more than once in all of the following: as the root node of a Scene, the children ObservableList of a Parent, or as the clip of a Node.

The scene graph must not have cycles. A cycle would exist if a node is an ancestor of itself in the tree, considering the Group content ObservableList, Parent children ObservableList, and Node clip relationships mentioned above.

If a program adds a child node to a Parent (including Group, Region, etc) and that node is already a child of a different Parent or the root of a Scene, the node is automatically (and silently) removed from its former parent. If a program attempts to modify the scene graph in any other way that violates the above rules, an exception is thrown, the modification attempt is ignored and the scene graph is restored to its previous state.

It is possible to rearrange the structure of the scene graph, for example, to move a subtree from one location in the scene graph to another. In order to do this, one would normally remove the subtree from its old location before inserting it at the new location. However, the subtree will be automatically removed as described above if the application doesn't explicitly remove it.

Here is a sample of multiple animated images in a single scene. In the example, multiple nodes are used, each sharing the same Image data. Because Image is not a Node, it can be shared without issue:

• How show specific part of an image in javafx