title: Consumer not rebuilding UI using riverpod
body: <p>I'm trying to make simple stateNotifier with riverpod. When I click the button, it'll toggle between values. I've checked the value and it changes when pressing the button. The problem is the UI is not rebuilding itself. I've checked the docs and am pretty sure I've done correctly.</p>
  <p><strong>Homescreen</strong></p>
  <pre><code>class HomeScreen extends StatefulWidget {
    @override
    _HomeScreenState createState() =&gt; _HomeScreenState();
  }
  
  class _HomeScreenState extends State&lt;HomeScreen&gt; {
  
    @override
    void initState() {
      super.initState();
    }
    @override
    Widget build(BuildContext context) {
      return SafeArea(
        child: Consumer(
          builder: (context, watch, child) {
            final drawer = watch(drawerProvider.state);
            return Container(
              width: MediaQuery.of(context).size.width,
              child: Column(
                children: [
                  Text(drawer.isOpen.toString()),
                  Text(drawer.x.toString()),
                  Text(drawer.y.toString()),
                  Text(drawer.scale.toString()),
                  FloatingActionButton(
                    onPressed: (){
                      context.read(drawerProvider).toggleDrawer();
                    }
                  )
                ],
              ),
            );
          },
        ),
      );
    }
  }
  </code></pre>
  <p><strong>Provider</strong></p>
  <pre><code>import 'package:flutter_riverpod/all.dart';
  
  class Drawer{
    double x,y,scale;
    bool isOpen;
    Drawer(this.x,this.y,this.scale,this.isOpen);
  }
  
  class DrawerNotifier extends StateNotifier&lt;Drawer&gt;{
    DrawerNotifier() : super(Drawer(0,0,1,false));
    void toggleDrawer(){
      if(state.isOpen){
        state.x = 0;
        state.y = 0;
        state.scale = 1;
      }else{
        state.x = 0.5;
        state.y = 0.1;
        state.scale = 0.8;
      }
      state.isOpen = !state.isOpen;
    }
  }
  
  final drawerProvider = StateNotifierProvider((ref) =&gt; new DrawerNotifier());
  </code></pre>