Update example app

-/*import 'package:flutter/widgets.dart';
+import 'package:flutter/widgets.dart';
 import 'src/first_method.dart' as firstMethod;
 import 'src/second_method.dart' as secondMethod;
 
@@ -6,106 +6,3 @@ void main() {
   const method = int.fromEnvironment('method', defaultValue: 1);
   runApp(method == 1 ? firstMethod.MyApp() : secondMethod.MyApp());
 }
-*/
-
-import 'dart:async';
-
-import 'package:flutter/material.dart';
-import 'package:flutter_screenutil/flutter_screenutil.dart';
-
-void main() {
-  runApp(ScreenUtilInit(
-    builder: (child) => MaterialApp(
-      key: GlobalObjectKey('screenutil'),
-      theme: ThemeData(
-        textTheme: TextTheme(
-          bodyText2: TextStyle(fontSize: 32.sp),
-        ),
-      ),
-      home: child,
-    ),
-    child: ThirdPage(),
-  ));
-}
-
-class MyStatelessElement<T extends TestPage> extends StatelessElement {
-  MyStatelessElement(T widget) : super(widget);
-
-  @override
-  T get widget => super.widget as T;
-
-  @override
-  void mount(Element? parent, Object? newSlot) {
-    super.mount(parent, newSlot);
-    print('${widget.text()} is mounted');
-  }
-
-  @override
-  void unmount() {
-    print('${widget.text()} is unmounted');
-    super.unmount();
-  }
-}
-
-abstract class TestPage extends StatelessWidget {
-  String text() => runtimeType.toString();
-
-  Widget goto();
-
-  @override
-  StatelessElement createElement() => MyStatelessElement(this);
-
-  @override
-  Widget build(BuildContext context) {
-    Timer(const Duration(seconds: 5), () {
-      Navigator.of(context).pushAndRemoveUntil(
-        MaterialPageRoute(builder: (context) => goto()),
-        (route) => false,
-      );
-    });
-    return Scaffold(
-      body: SafeArea(
-        child: Padding(
-          padding: const EdgeInsets.all(20).r,
-          child: Column(
-            mainAxisSize: MainAxisSize.min,
-            children: [
-              TextField(),
-              Text(
-                text(),
-                style: TextStyle(fontSize: 32.sp),
-              ),
-              Text(text()),
-              Expanded(
-                child: ListView.separated(
-                  shrinkWrap: true,
-                  itemBuilder: (context, index) => Text('$index'),
-                  separatorBuilder: (_, __) => Container(
-                    height: 50.h,
-                    color: Colors.green,
-                  ),
-                  itemCount: 10,
-                ),
-              ),
-            ],
-          ),
-        ),
-      ),
-    );
-  }
-}
-
-class FirstPage extends TestPage {
-  @override
-  Widget goto() => SecondPage();
-}
-
-class SecondPage extends TestPage {
-  @override
-  Widget goto() => FirstPage();
-}
-
-class ThirdPage extends TestPage {
-  @override
-  Widget goto() => FirstPage();
-}

@@ -57,6 +57,7 @@ class MyThemedApp extends StatelessWidget {
       debugShowCheckedModeBanner: false,
       title: 'First Method (Themed)',
       builder: (ctx, child) {
+        ScreenUtil.init(ctx);
         return Theme(
           data: ThemeData(
             primarySwatch: Colors.blue,

@@ -56,6 +56,7 @@ class MyThemedApp extends StatelessWidget {
       debugShowCheckedModeBanner: false,
       title: '第二种方法（带主题）',
       builder: (ctx, child) {
+        ScreenUtil.init(ctx);
         return Theme(
           data: ThemeData(
             primarySwatch: Colors.blue,