How to use Defaultabcontroller with Provider in flutter - flutter

Question

Condition don't work with StatelessWidget and Provider in Flutter,
Hopefully, I need that FloatingActionButton show up in specific tab but current code does not work properly. FloatingActionButton work in all tab.
I tried to debug and found index value is reflected but the Button does not disappear when changing tab.
return DefaultTabController(
length: 3,
initialIndex: 0,
child: ChangeNotifierProvider<MainModel>(
create: (_) => MainModel()..getWorkoutListRealtime(),
child: Scaffold(
appBar: AppBar(
title: Text("Workout at home"),
actions: [
Consumer<MainModel>(builder: (context, model, child) {
final isActive = model.checkShouldActiveCompleteButton();
return FlatButton(
onPressed: isActive
? () async {
await model.deleteCheckedItems();
}
: null,
child: Text(
'削除',
style: TextStyle(
color:
isActive ? Colors.white : Colors.white.withOpacity(0.5),
),
),
);
})
],
bottom: TabBar(
tabs: [
Tab(icon: Icon(Icons.directions_car)),
Tab(icon: Icon(Icons.directions_transit)),
Tab(icon: Icon(Icons.directions_bike)),
],
),
),
body: TabBarView(
children: [
Consumer<MainModel>(builder: (context, model, child) {
------------------------------------------------------------------
Consumer<MainModel>(builder: (context, model, child) {
return SimpleDatumLegend.withSampleData(model);
}),
CountdownTimer(),
],
),
floatingActionButton:
Consumer<MainModel>(builder: (context, model, child) {
final index = DefaultTabController.of(context).index;
return index == 1
? FloatingActionButton(
onPressed: () async {
await Navigator.push(
context,
MaterialPageRoute(
builder: (context) => AddPage(model),
fullscreenDialog: true,
),
);
},
child: Icon(Icons.touch_app),
)
: SizedBox.shrink();
}),
I use DefaultTabController because I use Stateless widget and Provider function.