Flatter:试图使用InheritedWidget,但得到空值

我在调用 of 功能 InheritedWidget ,但我的函数返回null,正如您在上面看到的,我的小部件位于树的顶部。调用来自一个被推到导航器堆栈上的页面,而不是这个页面。有人知道为什么吗?我的 继承小部件 代码如下。

class LiveKHProvider extends InheritedWidget {
  final LiveKHBloc liveKHBloc = LiveKHBloc();

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) => oldWidget != this;

  static LiveKHBloc of(BuildContext context) {
    var inheritFromWidgetOfExactType =
        context.inheritFromWidgetOfExactType(LiveKHProvider); // to clearly see what’s returning null. 
        //This is where it returns null, 
        //so the below line is executed on a null object.
    return (inheritFromWidgetOfExactType as LiveKHProvider).liveKHBloc;
  }

  LiveKHProvider({Key key, Widget child}) : super(key: key, child: child);
}