MeasureOverride ArrangeOverride

protected override Size MeasureOverride(Size constraint){if (constraint.Width == double.PositiveInfinity || constraint.Height == double.PositiveInfinity)return Size.Empty;UpdateScrollInfo(constraint);foreach (UIElement child in InternalChildren){child.Measure(ChildSize);}return constraint;}protected override Size ArrangeOverride(Size finalSize){UpdateScrollInfo(finalSize);for (int i = 0; i < InternalChildren.Count; i++){InternalChildren[i].Arrange(new Rect(new Point(i*ChildSize.Width, 0), ChildSize));}return finalSize;}

层层传递的作用，本自定义容器类定义这两个函数提供给它的上层容器调用，上层容器负责给下层的内容分配空间大小，以此来确定整个界面的布局。