Flutter 之A value of type ‘‘ can‘t be assigned to a variable of type的错误解决笔记

最近工作不是很忙，于是乎又是捡起Flutter继续学习。在github上找到一个flutter的学习demo，准备学习学习其动画。 运行github上的代码发下了如下错误：

Error: A value of type 'Animation' can't be assigned to a variable of type 
'Animation' because 'BorderRadius