Flutter Column等容器嵌套ListView报错

我爱模板网在用flutter做个效果时，需要用column嵌套ListView，这时会报错：

I/flutter ( 4625): EXCEPTION CAUGHT BY RENDERING LIBRARY
I/flutter ( 4625): The following assertion was thrown during performResize():
I/flutter ( 4625): Vertical viewport was given unbounded height.
I/flutter ( 4625): Viewports expand in the scrolling direction to fill their container.In this case, a vertical
I/flutter ( 4625): viewport was given an unlimited amount of vertical space in which to expand. This situation
I/flutter ( 4625): typically happens when a scrollable widget is nested inside another scrollable widget.
I/flutter ( 4625): If this widget is always nested in a scrollable widget there is no need to use a viewport because
I/flutter ( 4625): there will always be enough vertical space for the children. In this case, consider using a Column
I/flutter ( 4625): instead. Otherwise, consider using the “shrinkWrap” property (or a ShrinkWrappingViewport) to size
I/flutter ( 4625): the height of the viewport to the sum of the heights of its children.

这时，在listview外面嵌套一个expanded，或者一个container就可以了，尺寸计算的问题，expande就是listview有多大就有多大,container就是container多大listview就有多大，可以滚动，也不会报错了：

new Expanded(
    child: new ListView(
        .....
    )
);

这告诉ListView尽可能地获取宽度和高度。