Flutter Provider 调用Element.updata(widget)报错

如何解决Flutter Provider 调用Element.updata(widget)报错

想模仿Android的fragment切换效果，通过fragment动态更新FrameLayout布局。但是在项目中使用provider时，调用element时会出现异常。更新（协变小部件、新小部件）。

异常捕获==========

veg(i)

简化后的代码如下（可以直接运行）。 点击顶部按钮切换widget

The following assertion was thrown while handling a gesture:
    'package:flutter/src/widgets/framework.dart': Failed assertion: line 3439 pos 7: '_lifecycleState == _ElementLifecycle.active
            && widget != null
            && newWidget != null
            && newWidget != widget
            && depth != null
            && Widget.canUpdate(widget,newWidget)': is not true.


    Either the assertion indicates an error in the framework itself,or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
    In either case,please report this assertion by filing a bug on GitHub:
      https://github.com/flutter/flutter/issues/new?template=2_bug.md

    When the exception was thrown,this was the stack: 
    #2      Element.update (package:flutter/src/widgets/framework.dart:3439:7)
    #3      StatefulElement.update (package:flutter/src/widgets/framework.dart:4751:11)
    #4      _HomePageState.itemWidget.<anonymous closure>.<anonymous closure> (package:flutter_app/a/ui/page/home_page.dart:192:25)
    #5      BuildOwner.lockState (package:flutter/src/widgets/framework.dart:2473:15)
    #6      _HomePageState.itemWidget.<anonymous closure> (package:flutter_app/a/ui/page/home_page.dart:191:27)
    ...
    Handler: "onTap"
    Recognizer: TapGestureRecognizer#2d601
      debugOwner: GestureDetector
      state: ready
      won arena
      finalPosition: Offset(120.0,195.0)
      finalLocalPosition: Offset(40.0,33.5)
      button: 1
      sent tap down