flutter Error: The parameter ‘key‘ can‘t have a value of ‘null‘ because of its type ‘Key‘

解释比较深入的博客：
flutter null safety

• 如下图，把Key设置为可选参数就可以了
  
  参考博客：
  Flutter2.2中提示 The parameter ‘key’ can’t have a value of ‘null’ because of its type
  【错误记录】Flutter 编译报错 ( The parameter ‘‘ can‘t have a value of ‘null‘ because of its type, but the im )