Flutter using Mixin correctly - flutter

Question

I am looking to create two widgets that are similar and therefore should share some code.
I have made.a mixin that looks like this
import 'package:flutter/material.dart';
mixin WidgetShared <T extends StatefulWidget> on State<T>, TickerProviderStateMixin<T>{
AnimationController controlsAnimationController;
Animation<double> controlsAnimation;
bool controlsOpen = false;
#override
void initState() {
super.initState();
print("This was the init");
controlsAnimationController = AnimationController(
duration: const Duration(milliseconds: 400), vsync: this);
controlsAnimation = CurvedAnimation(
parent: controlsAnimationController, curve: Curves.easeInOut);
}
#override
void dispose() {
controlsAnimationController.dispose();
super.dispose();
}
void toggleControls(bool disableClicks) {
if (disableClicks == false) {
if (controlsAnimationController.value > 0) {
setState(() {
controlsOpen = false;
});
controlsAnimationController.reverse();
} else {
setState(() {
controlsOpen = true;
});
controlsAnimationController.forward();
}
}
}
void closeControls() {
if (controlsAnimationController.value > 0) {
setState(() {
controlsOpen = false;
});
controlsAnimationController.reverse();
}
}
}
Which both of the widgets use e.g.
class _Widget1State extends State<MediaViewer>
with TickerProviderStateMixin, SuperMediaViewer{
I can then reference the controlsOpen, controlsOpen and toggleControls() in both widgets easily.
However if i keep changing switching pages on the app I get this error which originates in one of my Provider State objects.
I/flutter (31161): ══╡ EXCEPTION CAUGHT BY FOUNDATION LIBRARY ╞════════════════════════════════════════════════════════
I/flutter (31161): The following assertion was thrown while dispatching notifications for NewUserDetailsState:
I/flutter (31161): setState() or markNeedsBuild() called when widget tree was locked.
I/flutter (31161): This _DefaultInheritedProviderScope<NewUserDetailsState> widget cannot be marked as needing to build
I/flutter (31161): because the framework is locked.
I/flutter (31161): The widget on which setState() or markNeedsBuild() was called was:
I am clearly not doing something right but I'm unsure what. I would be very grateful if someone could point me in the right direction.
Thanks