ProviderNotFoundException was thrown building Consumer

I have the following class in my Flutter app:

class SubTemasScreen extends StatefulWidget {
const SubTemasScreen({Key? key}) : super(key: key);
@override
State<SubTemasScreen> createState() => _SubTemasScreenState();
}
class _SubTemasScreenState extends State<SubTemasScreen> {
final TextEditingController _controller = TextEditingController();
Timer? timer;
bool verTodos = true;
bool verActivos = false;
bool verNoActivos = false;
bool verAdmin = false;
bool verCosmicos = false;
bool verMecenas = false;
bool verVerificados = false;
bool verNoVerificados = false;
void initTimer() {
if (timer != null && timer!.isActive) return;
timer = Timer.periodic(const Duration(seconds: 5), (timer) {
//job
setState(() {});
});
}
bool _esActivo = true;
String miEmail = "";
Future getData() async {
var url = Constantes().urlAPI + "get_datos_usuario.php";
http.Response response = await http.get(Uri.parse(url));
List data = json.decode(response.body);
User? usuarioActual = FirebaseAuth.instance.currentUser;
if (usuarioActual != null) {
miEmail = usuarioActual.email!;
print("miEmail es ${miEmail}");
for (var i = 0; i < data.length; i++) {
String s = data![i]["email"];
if (s == miEmail) {
var activo = data![i]["activo"];
print("activo ${activo}");
if (activo == "1") {
_esActivo = true;
} else {
_esActivo = false;
}
}
}
}
}
@override
void initState() {
super.initState();
getEmailUsuarioActual();
initTimer();
}
@override
void dispose() {
timer?.cancel();
super.dispose();
}
getEmailUsuarioActual() {
getData();
}
//EVITAR BACK BUTTON
Future<bool> _onWillPop() async {
return false; //<-- SEE HERE
}
@override
Widget build(BuildContext context) {
var filtrado = "0";
return _esActivo
? WillPopScope(
onWillPop: _onWillPop,
child: SafeArea(
child: Scaffold(
body: Consumer<TemasProvider>(
builder: (context, proveedor, _) {
return Column(
children: [
FilaSuperiorPantallas(),
SizedBox(
height: 15,
),
BuscadorTextField(
controller: _controller,
hintText: "Buscar sub-temas por título",
),
SizedBox(
height: 8,
),
//lista de temas para filtrar subtemas
Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
Text("Selecciona un tema para filtrar"),
filtrado != "0"
? IconButton(
onPressed: () {},
icon: Icon(
Icons.filter_alt_off_outlined,
size: 23,
))
: IconButton(
onPressed: () {},
icon: Icon(
Icons.filter_alt,
size: 23,
))
],
),
ListaTemasHorizontalLight(),
//LISTA DE sub TEMAS TODOS
ListaSubtemasTodos(controller: _controller)
],
);
}),
),
),
)
: NoActivo();
}
Future<Null> refresh() async {
await Future.delayed(Duration(seconds: 2));
setState(() {});
}
}

I am getting the following exception at line:

  body: Consumer<TemasProvider>(
builder: (context, proveedor, _) {

I have declared TemasProvider at the top of the widgets tree:

class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'MYSTERYMAP ADMIN',
theme: ThemeData(
primarySwatch: Colors.grey,
),
home: MultiProvider(providers: [
ChangeNotifierProvider(create: (_) => AutenticacionProvider()),
ChangeNotifierProvider(create: (_) => TemasProvider()),
], child: WidgetTree()),
);
}
}

This is the exception output:

======== Exception caught by widgets library =======================================================
The following ProviderNotFoundException was thrown building Consumer<TemasProvider>:
Error: Could not find the correct Provider<TemasProvider> above this Consumer<TemasProvider> Widget
This happens because you used a `BuildContext` that does not include the provider
of your choice. There are a few common scenarios:
- You added a new provider in your `main.dart` and performed a hot-reload.
To fix, perform a hot-restart.
- The provider you are trying to read is in a different route.
Providers are "scoped". So if you insert of provider inside a route, then
other routes will not be able to access that provider.
- You used a `BuildContext` that is an ancestor of the provider you are trying to read.
Make sure that Consumer<TemasProvider> is under your MultiProvider/Provider<TemasProvider>.
This usually happens when you are creating a provider and trying to read it immediately.

EDIT

Here you TemasProvider class:

import 'package:flutter/material.dart';

class TemasProvider extends ChangeNotifier {
String temaActual= "0";
void cambiarTemaActualState(String s) {
temaActual = s;
notifyListeners();
}
}

If you want your provider(s) to be available everywhere in the widget tree (on all screens), you should provide it above the MaterialApp widget. So, in your case, you should wrap your MaterialApp widget with your MultiProvider like this:

class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider(create: (_) => AutenticacionProvider()),
ChangeNotifierProvider(create: (_) => TemasProvider()),
],
child: MaterialApp(
debugShowCheckedModeBanner: false,
title: 'MYSTERYMAP ADMIN',
theme: ThemeData(
primarySwatch: Colors.grey,
),
home: WidgetTree(),
),
);
}
}