removeItem method
Implementation
void removeItem(K itemKey, {bool animate = true}) {
_checkNotDisposed();
_requireItem(itemKey, "removeItem");
_tree.remove(key: ItemKey<K>(itemKey), animate: animate);
}
void removeItem(K itemKey, {bool animate = true}) {
_checkNotDisposed();
_requireItem(itemKey, "removeItem");
_tree.remove(key: ItemKey<K>(itemKey), animate: animate);
}