GComponentSetChildIndexBefore Method

Moves a child to a certain position which is in front of the child previously at given index. 与SetChildIndex不同的是，如果child原来在index的前面，那么child插入的位置是index-1，即保证排在原来占据index的对象的前面。

public int SetChildIndexBefore(
	GObject child,
	int index
)