static void removeFromLayers(Shape shape) {
if (!layerOf.containsKey(shape)) return;
int oldLayer = layerOf.get(shape);
layerContents.get(oldLayer).remove(shape);
if (layerContents.get(oldLayer).isEmpty()) {
layerContents.remove(oldLayer);
layers.remove((Integer) oldLayer);
}
layerOf.remove(shape);
}
/**
* Set the layer that a given shape will be displayed in. Since the shapes in this game are two
* dimensional, it must be decided which will appear "on top" when two shapes overlap. The shape
* in the higher layer will appear on top.
*
* <p>Setting a shape's layer will only affect how it is displayed; a shape's layer has no effect
* on how it interacts with other shapes. (For example, two shapes can touch even if they are in
* different layers. See {@link Shape#isTouching(Shape)}.)
*
* @param shape the shape whose layer is being set.
* @param layer the layer into which this shape will be moved.
*/
static void setLayer(Shape shape, int layer) {
removeFromLayers(shape);
// add new stuff
if (!layerContents.containsKey(layer)) {
layerContents.put(layer, new CopyOnWriteArrayList<Shape>());
int insertionPoint = ~Collections.binarySearch(layers, layer);
layers.add(insertionPoint, layer);
}
layerContents.get(layer).add(shape);
layerOf.put(shape, layer);
}
/**
* Get the layer that the given shape is in. See {@link #setLayer} for more information about
* layers.
*
* @param shape the shape whose layer index will be returned.
* @return the index of the layer that <code>shape</code> is contained in.
* @see #setLayer
*/
static int getLayerOf(Shape shape) {
return layerOf.get(shape);
}