Fluuter 开发Column 报错NoSuchMethodError: The method ‘＞’ was called on null.

这个问题一般是在Column 中使用了ListView 导致。需要将ListVie w。外层 包裹Expanded。或者 Flex 控件才可以 

Column(children: <Widget>[getTopWidget(),Expanded(child: ListView.separated(itemBuilder: (context,index){return getListItem(index);},separatorBuilder: (context, index) => Divider(height: .0),itemCount: newList.length))],