Error reporting is shown in figure 
Problem code
import 'package:flutter/material.dart';
void main() {
runApp(SampleAppPage());
}
class SampleAppPage extends StatefulWidget {
const SampleAppPage({Key?key}) : super(key: key);
@override
_SampleAppPageState createState() => _SampleAppPageState();
}
class _SampleAppPageState extends State<SampleAppPage>
with SingleTickerProviderStateMixin {
late AnimationController controller;
late CurvedAnimation curve;
@override
void initState() {
super.initState();
controller = AnimationController(
duration: const Duration(milliseconds: 2000),
vsync: this,
);
curve = CurvedAnimation(
parent: controller,
curve: Curves.easeIn,
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: GestureDetector(
child: RotationTransition(
turns: curve,
child: const FlutterLogo(size: 200.0),
),
onDoubleTap: () {
if (controller.isCompleted) {
controller.reverse();
} else {
controller.forward();
}
},
),
),
);
}
}
Reason: the root component of the fluent interface must be MaterialApp
Code after repair
import 'package:flutter/material.dart';
void main() {
runApp(SampleApp());
}
class SampleApp extends StatelessWidget {
// This widget is the root of your application.
const SampleApp({Key?key}) : super(key: key);
@override
Widget build(BuildContext context) {
return const MaterialApp(
title: 'Sample App',
home: SampleAppPage(),
);
}
}
class SampleAppPage extends StatefulWidget {
const SampleAppPage({Key?key}) : super(key: key);
@override
_SampleAppPageState createState() => _SampleAppPageState();
}
class _SampleAppPageState extends State<SampleAppPage>
with SingleTickerProviderStateMixin {
late AnimationController controller;
late CurvedAnimation curve;
@override
void initState() {
super.initState();
controller = AnimationController(
duration: const Duration(milliseconds: 2000),
vsync: this,
);
curve = CurvedAnimation(
parent: controller,
curve: Curves.easeIn,
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: GestureDetector(
child: RotationTransition(
turns: curve,
child: const FlutterLogo(size: 200.0),
),
onDoubleTap: () {
if (controller.isCompleted) {
controller.reverse();
} else {
controller.forward();
}
},
),
),
);
}
}
