diff --git a/example/.fvm/fvm_config.json b/example/.fvm/fvm_config.json
new file mode 100644
index 0000000..7f3778c
--- /dev/null
+++ b/example/.fvm/fvm_config.json
@@ -0,0 +1,4 @@
+{
+  "flutterSdkVersion": "2.2.0",
+  "flavors": {}
+}
\ No newline at end of file
diff --git a/example/lib/codeviewer/code_style.dart b/example/lib/codeviewer/code_style.dart
index 7297bc4..8754484 100644
--- a/example/lib/codeviewer/code_style.dart
+++ b/example/lib/codeviewer/code_style.dart
@@ -14,19 +14,19 @@ class CodeStyle extends InheritedWidget {
     this.punctuationStyle,
     this.classStyle,
     this.constantStyle,
-    @required Widget child,
+    required Widget child,
   }) : super(child: child);
 
-  final TextStyle baseStyle;
-  final TextStyle numberStyle;
-  final TextStyle commentStyle;
-  final TextStyle keywordStyle;
-  final TextStyle stringStyle;
-  final TextStyle punctuationStyle;
-  final TextStyle classStyle;
-  final TextStyle constantStyle;
+  final TextStyle? baseStyle;
+  final TextStyle? numberStyle;
+  final TextStyle? commentStyle;
+  final TextStyle? keywordStyle;
+  final TextStyle? stringStyle;
+  final TextStyle? punctuationStyle;
+  final TextStyle? classStyle;
+  final TextStyle? constantStyle;
 
-  static CodeStyle of(BuildContext context) {
+  static CodeStyle? of(BuildContext context) {
     return context.dependOnInheritedWidgetOfExactType<CodeStyle>();
   }
 
diff --git a/example/lib/common/base_page.dart b/example/lib/common/base_page.dart
index 5d1bf53..ab1211b 100644
--- a/example/lib/common/base_page.dart
+++ b/example/lib/common/base_page.dart
@@ -6,12 +6,12 @@ import 'code_view.dart';
 class BasePage extends StatelessWidget {
   final String title;
   final Widget body;
-  final List<Widget> actions;
-  final CodeBuilder codeBuilder;
+  final List<Widget>? actions;
+  final CodeBuilder? codeBuilder;
   const BasePage(
-      {Key key,
-      @required this.title,
-      @required this.body,
+      {Key? key,
+      required this.title,
+      required this.body,
       this.actions,
       this.codeBuilder})
       : super(key: key);
diff --git a/example/lib/common/code_tile.dart b/example/lib/common/code_tile.dart
index e5e411f..1f9268c 100644
--- a/example/lib/common/code_tile.dart
+++ b/example/lib/common/code_tile.dart
@@ -4,10 +4,10 @@ import 'package:get/get.dart';
 import 'code_view.dart';
 
 class CodeTile extends StatelessWidget {
-  final Widget title;
-  final Widget subTitle;
-  final CodeBuilder builder;
-  const CodeTile({Key key, this.title, this.subTitle, this.builder})
+  final Widget? title;
+  final Widget? subTitle;
+  final CodeBuilder? builder;
+  const CodeTile({Key? key, this.title, this.subTitle, this.builder})
       : super(key: key);
 
   @override
diff --git a/example/lib/common/code_view.dart b/example/lib/common/code_view.dart
index f3aaea8..d1882ba 100644
--- a/example/lib/common/code_view.dart
+++ b/example/lib/common/code_view.dart
@@ -5,9 +5,9 @@ import '../codeviewer/code_style.dart';
 typedef CodeBuilder = TextSpan Function(BuildContext context);
 
 class CodeView extends StatefulWidget {
-  final CodeBuilder text;
+  final CodeBuilder? text;
   final String title;
-  CodeView({Key key, @required this.text, this.title = 'Code'})
+  CodeView({Key? key, required this.text, this.title = 'Code'})
       : super(key: key);
 
   @override
@@ -33,7 +33,7 @@ class _CodeViewState extends State<CodeView> {
             classStyle: codeTheme.copyWith(color: Colors.yellow),
             constantStyle: codeTheme.copyWith(color: Colors.pink),
             child:
-                Builder(builder: (context) => Text.rich(widget.text(context))),
+                Builder(builder: (context) => Text.rich(widget.text!(context))),
           )),
     );
   }
diff --git a/example/lib/component/example_scaffold.dart b/example/lib/component/example_scaffold.dart
index ca6011a..f882e48 100644
--- a/example/lib/component/example_scaffold.dart
+++ b/example/lib/component/example_scaffold.dart
@@ -5,13 +5,13 @@ import 'package:get/get.dart';
 
 class ExampleScaffold extends StatelessWidget {
   final String title;
-  final CodeBuilder text;
+  final CodeBuilder? text;
   final List<Widget> children;
   const ExampleScaffold({
-    Key key,
-    @required this.title,
+    Key? key,
+    required this.title,
     this.text,
-    @required this.children,
+    required this.children,
   }) : super(key: key);
 
   @override
diff --git a/example/lib/data/color_object.dart b/example/lib/data/color_object.dart
index 5a82f42..c001529 100644
--- a/example/lib/data/color_object.dart
+++ b/example/lib/data/color_object.dart
@@ -2,9 +2,9 @@ import 'package:ansu_ui/ansu_ui.dart';
 import 'package:flutter/material.dart';
 
 class ColorObject {
-  Color color;
-  String name;
-  String codeName;
+  Color? color;
+  String? name;
+  String? codeName;
   ColorObject({
     this.color,
     this.name,
diff --git a/example/lib/extension/example_list_ext.dart b/example/lib/extension/example_list_ext.dart
index 3ba2945..7777280 100644
--- a/example/lib/extension/example_list_ext.dart
+++ b/example/lib/extension/example_list_ext.dart
@@ -6,7 +6,7 @@ import 'package:flutter_screenutil/flutter_screenutil.dart';
 import 'package:velocity_x/velocity_x.dart';
 
 class ExampleListExt extends StatefulWidget {
-  const ExampleListExt({Key key}) : super(key: key);
+  const ExampleListExt({Key? key}) : super(key: key);
 
   @override
   _ExampleListExtState createState() => _ExampleListExtState();
diff --git a/example/lib/extension/example_num_ext.dart b/example/lib/extension/example_num_ext.dart
index dad37a8..f758839 100644
--- a/example/lib/extension/example_num_ext.dart
+++ b/example/lib/extension/example_num_ext.dart
@@ -5,7 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_screenutil/flutter_screenutil.dart';
 
 class ExampleNumExt extends StatefulWidget {
-  ExampleNumExt({Key key}) : super(key: key);
+  ExampleNumExt({Key? key}) : super(key: key);
 
   @override
   _ExampleNumExtState createState() => _ExampleNumExtState();
diff --git a/example/lib/extension/example_string_ext.dart b/example/lib/extension/example_string_ext.dart
index 28cf37b..449d092 100644
--- a/example/lib/extension/example_string_ext.dart
+++ b/example/lib/extension/example_string_ext.dart
@@ -4,7 +4,7 @@ import 'package:example/component/example_scaffold.dart';
 import 'package:flutter/material.dart';
 
 class ExampleStringExt extends StatefulWidget {
-  ExampleStringExt({Key key}) : super(key: key);
+  ExampleStringExt({Key? key}) : super(key: key);
 
   @override
   _ExampleStringExtState createState() => _ExampleStringExtState();
diff --git a/example/lib/main.dart b/example/lib/main.dart
index dff1d9d..7db318b 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -37,14 +37,14 @@ class MyApp extends StatelessWidget {
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({Key key}) : super(key: key);
+  MyHomePage({Key? key}) : super(key: key);
 
   @override
   _MyHomePageState createState() => _MyHomePageState();
 }
 
 class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
-  TabController _tabController;
+  TabController? _tabController;
 
   @override
   void initState() {
@@ -56,9 +56,9 @@ class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
 
   @override
   Widget build(BuildContext context) {
-    print(Theme.of(context).textTheme.headline1.fontFamily);
+    print(Theme.of(context).textTheme.headline1!.fontFamily);
     return ASScaffold(
-      leading: navigator.canPop()
+      leading: navigator!.canPop()
           ? IconButton(
               icon: Icon(Icons.backpack, color: Colors.black),
               onPressed: () {},
@@ -74,7 +74,7 @@ class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
         ],
       ),
       bottomNavigationBar: ASNavigationBar(
-        controller: _tabController,
+        controller: _tabController!,
         items: [
           BottomNavigationBarItem(
             icon: Icon(Icons.home),
diff --git a/example/lib/main_extention.dart b/example/lib/main_extention.dart
index b2bdc0c..f70d2d7 100644
--- a/example/lib/main_extention.dart
+++ b/example/lib/main_extention.dart
@@ -6,7 +6,7 @@ import 'package:flutter_screenutil/flutter_screenutil.dart';
 import 'package:get/get.dart';
 
 class MainExtention extends StatefulWidget {
-  MainExtention({Key key}) : super(key: key);
+  MainExtention({Key? key}) : super(key: key);
 
   @override
   _MainExtentionState createState() => _MainExtentionState();
@@ -14,9 +14,9 @@ class MainExtention extends StatefulWidget {
 
 class _MainExtentionState extends State<MainExtention> {
   _innerButton({
-    VoidCallback onPressed,
-    Widget child,
-    Widget icon,
+    VoidCallback? onPressed,
+    required Widget child,
+    Widget? icon,
   }) {
     return TextButton(
       onPressed: onPressed,
diff --git a/example/lib/main_home.dart b/example/lib/main_home.dart
index b6549e1..37e3ec3 100644
--- a/example/lib/main_home.dart
+++ b/example/lib/main_home.dart
@@ -21,7 +21,7 @@ import 'package:flutter_screenutil/flutter_screenutil.dart';
 import 'package:get/get.dart';
 
 class MainHome extends StatefulWidget {
-  MainHome({Key key}) : super(key: key);
+  MainHome({Key? key}) : super(key: key);
 
   @override
   _MainHomeState createState() => _MainHomeState();
@@ -29,15 +29,15 @@ class MainHome extends StatefulWidget {
 
 class _MainHomeState extends State<MainHome> {
   _innerButton({
-    VoidCallback onPressed,
-    String title,
-    IconData icon,
+    VoidCallback? onPressed,
+    required String title,
+    IconData? icon,
   }) {
     return TextButton(
       onPressed: onPressed,
       child: Row(
         children: [
-          Expanded(child: Icon(icon) ?? SizedBox()),
+          Expanded(child: icon != null ? Icon(icon) : SizedBox()),
           Text(title),
           Spacer(),
         ],
diff --git a/example/lib/main_utils.dart b/example/lib/main_utils.dart
index f9de411..a2b4443 100644
--- a/example/lib/main_utils.dart
+++ b/example/lib/main_utils.dart
@@ -4,7 +4,7 @@ import 'package:get/get.dart';
 import 'package:flutter_screenutil/flutter_screenutil.dart';
 
 class MainUtils extends StatefulWidget {
-  MainUtils({Key key}) : super(key: key);
+  MainUtils({Key? key}) : super(key: key);
 
   @override
   _MainUtilsState createState() => _MainUtilsState();
@@ -12,9 +12,9 @@ class MainUtils extends StatefulWidget {
 
 class _MainUtilsState extends State<MainUtils> {
   _innerButton({
-    VoidCallback onPressed,
-    Widget child,
-    Widget icon,
+    VoidCallback? onPressed,
+    required Widget child,
+    Widget? icon,
   }) {
     return TextButton(
       onPressed: onPressed,
diff --git a/example/lib/util_view/example_camera_view.dart b/example/lib/util_view/example_camera_view.dart
index 510a423..5da39dc 100644
--- a/example/lib/util_view/example_camera_view.dart
+++ b/example/lib/util_view/example_camera_view.dart
@@ -7,7 +7,7 @@ import 'package:flutter/material.dart';
 import 'package:velocity_x/velocity_x.dart';
 
 class ExampleCameraView extends StatefulWidget {
-  ExampleCameraView({Key key}) : super(key: key);
+  ExampleCameraView({Key? key}) : super(key: key);
 
   @override
   _ExampleCameraViewState createState() => _ExampleCameraViewState();
@@ -24,8 +24,8 @@ class _ExampleCameraViewState extends State<ExampleCameraView> {
         ListTile(
           title: 'CameraView'.text.make(),
           onTap: () async {
-            File file = await camView(context, title: 'TEST');
-            print(await file.length());
+            File? file = await camView(context, title: 'TEST');
+            print(await file?.length());
           },
         ),
         // END
diff --git a/example/lib/widgets/example_bottom_button.dart b/example/lib/widgets/example_bottom_button.dart
index b07f55b..93b8a0a 100644
--- a/example/lib/widgets/example_bottom_button.dart
+++ b/example/lib/widgets/example_bottom_button.dart
@@ -8,7 +8,7 @@ import 'package:get/get.dart';
 
 
 class ExampleBottomButton extends StatefulWidget {
-  ExampleBottomButton({Key key}) : super(key: key);
+  ExampleBottomButton({Key? key}) : super(key: key);
 
   @override
   _ExampleBottomButtonState createState() => _ExampleBottomButtonState();
diff --git a/example/lib/widgets/example_box.dart b/example/lib/widgets/example_box.dart
index 7e3cccb..7debbe9 100644
--- a/example/lib/widgets/example_box.dart
+++ b/example/lib/widgets/example_box.dart
@@ -3,7 +3,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_screenutil/flutter_screenutil.dart';
 
 class ExampleBox extends StatefulWidget {
-  ExampleBox({Key key}) : super(key: key);
+  ExampleBox({Key? key}) : super(key: key);
 
   @override
   _ExampleBoxState createState() => _ExampleBoxState();
diff --git a/example/lib/widgets/example_button.dart b/example/lib/widgets/example_button.dart
index 6e10aad..7c0c7fb 100644
--- a/example/lib/widgets/example_button.dart
+++ b/example/lib/widgets/example_button.dart
@@ -7,7 +7,7 @@ import 'package:flutter_screenutil/flutter_screenutil.dart';
 import 'package:get/get.dart';
 
 class ExampleButton extends StatefulWidget {
-  ExampleButton({Key key}) : super(key: key);
+  ExampleButton({Key? key}) : super(key: key);
 
   @override
   _ExampleButtonState createState() => _ExampleButtonState();
@@ -153,25 +153,25 @@ class _ExampleButtonState extends State<ExampleButton> {
                 groupValue: groupValue,
                 value: 0,
                 title: '候选0',
-                onTap: (_) => setState(() => groupValue = 0),
+                onTap: (dynamic _) => setState(() => groupValue = 0),
               ),
               ASRadioButton(
                 groupValue: groupValue,
                 value: 1,
                 title: '候选1',
-                onTap: (_) => setState(() => groupValue = 1),
+                onTap: (dynamic _) => setState(() => groupValue = 1),
               ),
               ASRadioButton(
                 groupValue: groupValue,
                 value: 2,
                 title: '候选2',
-                onTap: (_) => setState(() => groupValue = 2),
+                onTap: (dynamic _) => setState(() => groupValue = 2),
               ),
               ASRadioButton(
                 groupValue: groupValue,
                 value: 3,
                 title: '候选3',
-                onTap: (_) => setState(() => groupValue = 3),
+                onTap: (dynamic _) => setState(() => groupValue = 3),
               ),
             ],
           ),
diff --git a/example/lib/widgets/example_chart.dart b/example/lib/widgets/example_chart.dart
index 556bdb2..971c3f9 100644
--- a/example/lib/widgets/example_chart.dart
+++ b/example/lib/widgets/example_chart.dart
@@ -3,7 +3,7 @@ import 'package:ansu_ui/chart/circle_chart_widget.dart';
 import 'package:flutter/material.dart';
 
 class ExampleChart extends StatefulWidget {
-  const ExampleChart({Key key}) : super(key: key);
+  const ExampleChart({Key? key}) : super(key: key);
 
   @override
   _ExampleChartState createState() => _ExampleChartState();
diff --git a/example/lib/widgets/example_divider.dart b/example/lib/widgets/example_divider.dart
index 800829a..997e1f1 100644
--- a/example/lib/widgets/example_divider.dart
+++ b/example/lib/widgets/example_divider.dart
@@ -3,7 +3,7 @@ import 'package:ansu_ui/divider/as_dotted_divider.dart';
 import 'package:flutter/material.dart';
 
 class ExampleDivider extends StatefulWidget {
-  ExampleDivider({Key key}) : super(key: key);
+  ExampleDivider({Key? key}) : super(key: key);
 
   @override
   _ExampleDividerState createState() => _ExampleDividerState();
diff --git a/example/lib/widgets/example_drawer.dart b/example/lib/widgets/example_drawer.dart
index b43f32a..dc50226 100644
--- a/example/lib/widgets/example_drawer.dart
+++ b/example/lib/widgets/example_drawer.dart
@@ -2,7 +2,7 @@ import 'package:ansu_ui/ansu_ui.dart';
 import 'package:flutter/material.dart';
 
 class ExampleDrawer extends StatefulWidget {
-  ExampleDrawer({Key key}) : super(key: key);
+  ExampleDrawer({Key? key}) : super(key: key);
 
   @override
   _ExampleDrawerState createState() => _ExampleDrawerState();
diff --git a/example/lib/widgets/example_listtile.dart b/example/lib/widgets/example_listtile.dart
index cb7b47b..b630eb6 100644
--- a/example/lib/widgets/example_listtile.dart
+++ b/example/lib/widgets/example_listtile.dart
@@ -3,7 +3,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_screenutil/flutter_screenutil.dart';
 
 class ExampleListTile extends StatefulWidget {
-  ExampleListTile({Key key}) : super(key: key);
+  ExampleListTile({Key? key}) : super(key: key);
 
   @override
   _ExampleListTileState createState() => _ExampleListTileState();
diff --git a/example/lib/widgets/example_numeric_button.dart b/example/lib/widgets/example_numeric_button.dart
index 13db3e1..83f94ed 100644
--- a/example/lib/widgets/example_numeric_button.dart
+++ b/example/lib/widgets/example_numeric_button.dart
@@ -5,7 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:get/get.dart';
 
 class ExampleNumericButton extends StatefulWidget {
-  ExampleNumericButton({Key key}) : super(key: key);
+  ExampleNumericButton({Key? key}) : super(key: key);
 
   @override
   _ExampleNumericButtonState createState() => _ExampleNumericButtonState();
diff --git a/example/lib/widgets/example_picker.dart b/example/lib/widgets/example_picker.dart
index 0379ea1..8702021 100644
--- a/example/lib/widgets/example_picker.dart
+++ b/example/lib/widgets/example_picker.dart
@@ -7,7 +7,7 @@ import 'package:flutter/material.dart';
 import 'package:get/get.dart';
 
 class ExamplePicker extends StatefulWidget {
-  ExamplePicker({Key key}) : super(key: key);
+  ExamplePicker({Key? key}) : super(key: key);
 
   @override
   _ExamplePickerState createState() => _ExamplePickerState();
@@ -40,7 +40,7 @@ class _ExamplePickerState extends State<ExamplePicker> {
             trailing: ASButton(
               title: '日期选择器',
               onPressed: () async {
-                DateTime date = await asDatePicker(context);
+                DateTime? date = await asDatePicker(context);
                 Get.snackbar(date.toString(), 'MESSAGE');
               },
             ),
@@ -75,8 +75,8 @@ class _ExamplePickerState extends State<ExamplePicker> {
             trailing: ASButton(
               title: '图片选择器',
               onPressed: () async {
-                File file = await camView(context, title: '图片选择器');
-                print(file.lengthSync());
+                File? file = await camView(context, title: '图片选择器');
+                print(file?.lengthSync());
               },
             ),
           ),
@@ -86,7 +86,7 @@ class _ExamplePickerState extends State<ExamplePicker> {
             trailing: ASButton(
               title: '图片选择器',
               onPressed: () async {
-                File file = await pickImageFile();
+                File? file = await pickImageFile();
               },
             ),
           ),
diff --git a/example/lib/widgets/example_pop_up_menu.dart b/example/lib/widgets/example_pop_up_menu.dart
index dba4a58..ae54ccc 100644
--- a/example/lib/widgets/example_pop_up_menu.dart
+++ b/example/lib/widgets/example_pop_up_menu.dart
@@ -3,14 +3,14 @@ import 'package:flutter/material.dart';
 import 'package:velocity_x/velocity_x.dart';
 
 class ExamplePopUpMenu extends StatefulWidget {
-  ExamplePopUpMenu({Key key}) : super(key: key);
+  ExamplePopUpMenu({Key? key}) : super(key: key);
 
   @override
   _ExamplePopUpMenuState createState() => _ExamplePopUpMenuState();
 }
 
 class _ExamplePopUpMenuState extends State<ExamplePopUpMenu> {
-  int _value;
+  int? _value;
   @override
   Widget build(BuildContext context) {
     return ASScaffold(
@@ -25,7 +25,7 @@ class _ExamplePopUpMenuState extends State<ExamplePopUpMenu> {
                 return TextButton(
                   child: '$_value'.text.make(),
                   onPressed: () async {
-                    int result = await showASPopUpMenu<int>(
+                    int? result = await showASPopUpMenu<int>(
                       context: context,
                       initValue: _value,
                       items: List.generate(
diff --git a/example/lib/widgets/example_refresh.dart b/example/lib/widgets/example_refresh.dart
index 0051a18..56a3260 100644
--- a/example/lib/widgets/example_refresh.dart
+++ b/example/lib/widgets/example_refresh.dart
@@ -2,7 +2,7 @@ import 'package:ansu_ui/ansu_ui.dart';
 import 'package:flutter/material.dart';
 
 class ExampleRefresh extends StatefulWidget {
-  ExampleRefresh({Key key}) : super(key: key);
+  ExampleRefresh({Key? key}) : super(key: key);
 
   @override
   _ExampleRefreshState createState() => _ExampleRefreshState();
diff --git a/example/lib/widgets/example_scaffold.dart b/example/lib/widgets/example_scaffold.dart
index 35303f1..64b5246 100644
--- a/example/lib/widgets/example_scaffold.dart
+++ b/example/lib/widgets/example_scaffold.dart
@@ -6,7 +6,7 @@ import 'package:flutter/material.dart';
 import 'package:get/get.dart';
 
 class ExampleScaffold extends StatefulWidget {
-  ExampleScaffold({Key key}) : super(key: key);
+  ExampleScaffold({Key? key}) : super(key: key);
 
   @override
   _ExampleScaffoldState createState() => _ExampleScaffoldState();
@@ -14,15 +14,15 @@ class ExampleScaffold extends StatefulWidget {
 
 class _ExampleScaffoldState extends State<ExampleScaffold>
     with TickerProviderStateMixin {
-  TabController _tabController;
-  List<String> tabs;
+  late TabController _tabController;
+  List<String>? tabs;
 
   @override
   void initState() {
     super.initState();
     tabs = List.generate(10, (index) => 'Tab $index');
     _tabController = TabController(
-      length: tabs.length,
+      length: tabs!.length,
       vsync: this,
     );
   }
diff --git a/example/lib/widgets/example_style_color.dart b/example/lib/widgets/example_style_color.dart
index 8ad6bc8..0fd64db 100644
--- a/example/lib/widgets/example_style_color.dart
+++ b/example/lib/widgets/example_style_color.dart
@@ -4,7 +4,7 @@ import 'package:ansu_ui/ansu_ui.dart';
 import 'package:flutter_screenutil/flutter_screenutil.dart';
 
 class ExampleStyleColor extends StatefulWidget {
-  ExampleStyleColor({Key key}) : super(key: key);
+  ExampleStyleColor({Key? key}) : super(key: key);
 
   @override
   _ExampleStyleColorState createState() => _ExampleStyleColorState();
@@ -26,7 +26,7 @@ class _ExampleStyleColorState extends State<ExampleStyleColor> {
           ],
         ),
       ),
-      subtitle: Text(object.codeName),
+      subtitle: Text(object.codeName!),
       trailing: Card(
         color: object.color,
         child: SizedBox(height: 50.w, width: 50.w),
diff --git a/example/lib/widgets/example_tab_bar.dart b/example/lib/widgets/example_tab_bar.dart
index 14d343e..4f0671f 100644
--- a/example/lib/widgets/example_tab_bar.dart
+++ b/example/lib/widgets/example_tab_bar.dart
@@ -5,7 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:get/get.dart';
 
 class ExampleTabBar extends StatefulWidget {
-  ExampleTabBar({Key key}) : super(key: key);
+  ExampleTabBar({Key? key}) : super(key: key);
 
   @override
   _ExampleTabBarState createState() => _ExampleTabBarState();
@@ -13,10 +13,10 @@ class ExampleTabBar extends StatefulWidget {
 
 class _ExampleTabBarState extends State<ExampleTabBar>
     with TickerProviderStateMixin {
-  TabController _tabController1;
-  TabController _tabController2;
-  TabController _tabController3;
-  TabController _tabController4;
+  TabController? _tabController1;
+  TabController? _tabController2;
+  TabController? _tabController3;
+  TabController? _tabController4;
   @override
   void initState() {
     super.initState();
@@ -58,23 +58,23 @@ class _ExampleTabBarState extends State<ExampleTabBar>
             // BEGIN tabBar
             ASTabBar(
               items: ['全部', 'Part1', 'Part2'],
-              controller: _tabController1,
+              controller: _tabController1!,
             ),
             ASTabBar(
               items: List.generate(5, (index) => 'Tab $index'),
-              controller: _tabController2,
+              controller: _tabController2!,
             ),
             ASTabBar(
               isScrollable: true,
               items: List.generate(10, (index) => 'Tab $index'),
-              controller: _tabController3,
+              controller: _tabController3!,
             ),
             ASTabBar.tag(
               isScrollable: true,
               tabItems: List.generate(10, (index) => 'Tab $index')
                   .map((e) => ASTabBarItem(title: e, tag: e))
                   .toList(),
-              controller: _tabController4,
+              controller: _tabController4!,
             ),
 
             // END
diff --git a/example/lib/widgets/example_tag.dart b/example/lib/widgets/example_tag.dart
index ea6800e..9f97417 100644
--- a/example/lib/widgets/example_tag.dart
+++ b/example/lib/widgets/example_tag.dart
@@ -6,7 +6,7 @@ import 'package:flutter_screenutil/flutter_screenutil.dart';
 import 'package:velocity_x/velocity_x.dart';
 
 class ExampleTag extends StatefulWidget {
-  ExampleTag({Key key}) : super(key: key);
+  ExampleTag({Key? key}) : super(key: key);
 
   @override
   _ExampaleTagState createState() => _ExampaleTagState();
diff --git a/example/lib/widgets/example_text_field.dart b/example/lib/widgets/example_text_field.dart
index 54194bd..4ab7b63 100644
--- a/example/lib/widgets/example_text_field.dart
+++ b/example/lib/widgets/example_text_field.dart
@@ -2,14 +2,14 @@ import 'package:ansu_ui/ansu_ui.dart';
 import 'package:flutter/material.dart';
 
 class ExampleTextFiled extends StatefulWidget {
-  ExampleTextFiled({Key key}) : super(key: key);
+  ExampleTextFiled({Key? key}) : super(key: key);
 
   @override
   _ExampleTextFiledState createState() => _ExampleTextFiledState();
 }
 
 class _ExampleTextFiledState extends State<ExampleTextFiled> {
-  TextEditingController _controller;
+  TextEditingController? _controller;
   @override
   Widget build(BuildContext context) {
     return ASScaffold(
diff --git a/example/lib/widgets/example_toast.dart b/example/lib/widgets/example_toast.dart
index 72ec95e..79b34bb 100644
--- a/example/lib/widgets/example_toast.dart
+++ b/example/lib/widgets/example_toast.dart
@@ -5,7 +5,7 @@ import 'package:flutter/material.dart';
 import 'package:velocity_x/velocity_x.dart';
 
 class ExampleToast extends StatelessWidget {
-  const ExampleToast({Key key}) : super(key: key);
+  const ExampleToast({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
diff --git a/example/pubspec.lock b/example/pubspec.lock
index f805e34..5cdbb00 100644
--- a/example/pubspec.lock
+++ b/example/pubspec.lock
@@ -10,13 +10,6 @@ packages:
       url: "https://git.oa00.com/flutter_pub/animated_collection.git"
     source: git
     version: "0.0.1"
-  animator:
-    dependency: transitive
-    description:
-      name: animator
-      url: "https://pub.flutter-io.cn"
-    source: hosted
-    version: "3.0.0"
   ansu_ui:
     dependency: "direct main"
     description:
@@ -28,86 +21,93 @@ packages:
     dependency: "direct main"
     description:
       name: args
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.2.0"
   async:
     dependency: transitive
     description:
       name: async
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.5.0"
+    version: "2.8.2"
   auto_size_text_pk:
     dependency: transitive
     description:
       name: auto_size_text_pk
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "3.0.0"
   bot_toast:
     dependency: transitive
     description:
       name: bot_toast
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "4.0.1"
   characters:
     dependency: transitive
     description:
       name: characters
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.1"
   cli_util:
     dependency: transitive
     description:
       name: cli_util
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.3.0"
+    version: "0.3.3"
   clock:
     dependency: transitive
     description:
       name: clock
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.15.0"
+  cross_file:
+    dependency: transitive
+    description:
+      name: cross_file
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.3.1+4"
   cupertino_icons:
     dependency: "direct main"
     description:
       name: cupertino_icons
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.2"
+    version: "1.0.3"
   expandable:
     dependency: transitive
     description:
       name: expandable
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "5.0.1"
   file:
     dependency: transitive
     description:
       name: file
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "6.1.0"
+    version: "6.1.2"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -117,7 +117,7 @@ packages:
     dependency: transitive
     description:
       name: flutter_easyrefresh
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.2.1"
   flutter_localizations:
@@ -129,16 +129,16 @@ packages:
     dependency: transitive
     description:
       name: flutter_plugin_android_lifecycle
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.1"
+    version: "2.0.2"
   flutter_screenutil:
     dependency: transitive
     description:
       name: flutter_screenutil
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "5.0.0"
+    version: "5.0.0+2"
   flutter_web_plugins:
     dependency: transitive
     description: flutter
@@ -148,107 +148,107 @@ packages:
     dependency: "direct main"
     description:
       name: get
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.1.4"
+    version: "4.3.8"
   glob:
     dependency: transitive
     description:
       name: glob
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.1"
   grinder:
     dependency: "direct main"
     description:
       name: grinder
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.9.0"
   http:
     dependency: transitive
     description:
       name: http
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.13.1"
+    version: "0.13.3"
   http_parser:
     dependency: transitive
     description:
       name: http_parser
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "4.0.0"
   image_picker:
     dependency: transitive
     description:
       name: image_picker
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.7.4"
+    version: "0.7.5+4"
   image_picker_for_web:
     dependency: transitive
     description:
       name: image_picker_for_web
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.3"
   image_picker_platform_interface:
     dependency: transitive
     description:
       name: image_picker_platform_interface
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.1"
+    version: "2.3.0"
   intl:
     dependency: transitive
     description:
       name: intl
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.17.0"
   js:
     dependency: transitive
     description:
       name: js
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.6.3"
   lpinyin:
     dependency: transitive
     description:
       name: lpinyin
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.1"
+    version: "2.0.3"
   meta:
     dependency: transitive
     description:
       name: meta
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0"
   pedantic:
     dependency: transitive
     description:
       name: pedantic
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.11.0"
+    version: "1.11.1"
   plugin_platform_interface:
     dependency: transitive
     description:
       name: plugin_platform_interface
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.0.1"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -258,58 +258,51 @@ packages:
     dependency: transitive
     description:
       name: source_span
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.1"
-  states_rebuilder:
-    dependency: transitive
-    description:
-      name: states_rebuilder
-      url: "https://pub.flutter-io.cn"
-    source: hosted
-    version: "4.0.0+1"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.2.0"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.0"
   velocity_x:
     dependency: transitive
     description:
       name: velocity_x
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.6.1"
+    version: "3.3.0"
   vxstate:
     dependency: transitive
     description:
       name: vxstate
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.1"
+    version: "2.1.0"
 sdks:
   dart: ">=2.12.0 <3.0.0"
   flutter: ">=2.0.0"
diff --git a/example/pubspec.yaml b/example/pubspec.yaml
index 104325d..694d593 100644
--- a/example/pubspec.yaml
+++ b/example/pubspec.yaml
@@ -4,7 +4,7 @@ publish_to: "none"
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
@@ -17,7 +17,7 @@ dependencies:
   cupertino_icons: ^1.0.0
   ansu_ui:
     path: ../
-  get:
+  get: ^4.1.3
   grinder:
   args:
 
diff --git a/example/tool/codeviewer_cli/main.dart b/example/tool/codeviewer_cli/main.dart
index f292289..619be0e 100644
--- a/example/tool/codeviewer_cli/main.dart
+++ b/example/tool/codeviewer_cli/main.dart
@@ -25,7 +25,7 @@ void main(List<String> arguments) {
 
   writeSegments(
     sourceDirectoryPath: path.join(Directory.current.path, 'lib'),
-    targetFilePath: argResults['target'] as String,
+    targetFilePath: argResults['target'] as String?,
     isDryRun: argResults['dry-run'] as bool,
   );
 }
diff --git a/example/tool/codeviewer_cli/prehighlighter.dart b/example/tool/codeviewer_cli/prehighlighter.dart
index df9bd6b..252a56f 100644
--- a/example/tool/codeviewer_cli/prehighlighter.dart
+++ b/example/tool/codeviewer_cli/prehighlighter.dart
@@ -76,15 +76,15 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
     'bool',
   ];
 
-  String _src;
-  StringScanner _scanner;
+  String? _src;
+  late StringScanner _scanner;
 
-  List<_HighlightSpan> _spans;
+  late List<_HighlightSpan> _spans;
 
   @override
-  List<CodeSpan> format(String src) {
+  List<CodeSpan> format(String? src) {
     _src = src;
-    _scanner = StringScanner(_src);
+    _scanner = StringScanner(_src!);
 
     if (_generateSpans()) {
       // Successfully parsed the code
@@ -93,19 +93,19 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
 
       for (final span in _spans) {
         if (currentPosition != span.start) {
-          formattedText
-              .add(CodeSpan(text: _src.substring(currentPosition, span.start)));
+          formattedText.add(
+              CodeSpan(text: _src!.substring(currentPosition, span.start)));
         }
 
         formattedText
-            .add(CodeSpan(type: span.type, text: span.textForSpan(_src)));
+            .add(CodeSpan(type: span.type, text: span.textForSpan(_src!)));
 
         currentPosition = span.end;
       }
 
-      if (currentPosition != _src.length) {
-        formattedText
-            .add(CodeSpan(text: _src.substring(currentPosition, _src.length)));
+      if (currentPosition != _src!.length) {
+        formattedText.add(
+            CodeSpan(text: _src!.substring(currentPosition, _src!.length)));
       }
 
       return formattedText;
@@ -126,23 +126,23 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r'/\*(.|\n)*\*/'))) {
         _spans.add(_HighlightSpan(
           _HighlightType.comment,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
 
       // Line comments
       if (_scanner.scan('//')) {
-        final startComment = _scanner.lastMatch.start;
+        final startComment = _scanner.lastMatch!.start;
 
         var eof = false;
         int endComment;
         if (_scanner.scan(RegExp(r'.*\n'))) {
-          endComment = _scanner.lastMatch.end - 1;
+          endComment = _scanner.lastMatch!.end - 1;
         } else {
           eof = true;
-          endComment = _src.length;
+          endComment = _src!.length;
         }
 
         _spans.add(_HighlightSpan(
@@ -162,8 +162,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r'r".*"'))) {
         _spans.add(_HighlightSpan(
           _HighlightType.string,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -172,8 +172,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r"r'.*'"))) {
         _spans.add(_HighlightSpan(
           _HighlightType.string,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -182,8 +182,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r'"""(?:[^"\\]|\\(.|\n))*"""'))) {
         _spans.add(_HighlightSpan(
           _HighlightType.string,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -192,8 +192,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r"'''(?:[^'\\]|\\(.|\n))*'''"))) {
         _spans.add(_HighlightSpan(
           _HighlightType.string,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -202,8 +202,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r'"(?:[^"\\]|\\.)*"'))) {
         _spans.add(_HighlightSpan(
           _HighlightType.string,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -212,8 +212,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r"'(?:[^'\\]|\\.)*'"))) {
         _spans.add(_HighlightSpan(
           _HighlightType.string,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -222,8 +222,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r'\d+\.\d+'))) {
         _spans.add(_HighlightSpan(
           _HighlightType.number,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -231,7 +231,7 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       // Integer
       if (_scanner.scan(RegExp(r'\d+'))) {
         _spans.add(_HighlightSpan(_HighlightType.number,
-            _scanner.lastMatch.start, _scanner.lastMatch.end));
+            _scanner.lastMatch!.start, _scanner.lastMatch!.end));
         continue;
       }
 
@@ -239,8 +239,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r'[\[\]{}().!=<>&\|\?\+\-\*/%\^~;:,]'))) {
         _spans.add(_HighlightSpan(
           _HighlightType.punctuation,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
@@ -249,17 +249,17 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
       if (_scanner.scan(RegExp(r'@\w+'))) {
         _spans.add(_HighlightSpan(
           _HighlightType.keyword,
-          _scanner.lastMatch.start,
-          _scanner.lastMatch.end,
+          _scanner.lastMatch!.start,
+          _scanner.lastMatch!.end,
         ));
         continue;
       }
 
       // Words
       if (_scanner.scan(RegExp(r'\w+'))) {
-        _HighlightType type;
+        _HighlightType? type;
 
-        var word = _scanner.lastMatch[0];
+        var word = _scanner.lastMatch![0]!;
         if (word.startsWith('_')) {
           word = word.substring(1);
         }
@@ -279,8 +279,8 @@ class DartSyntaxPrehighlighter extends SyntaxPrehighlighter {
         if (type != null) {
           _spans.add(_HighlightSpan(
             type,
-            _scanner.lastMatch.start,
-            _scanner.lastMatch.end,
+            _scanner.lastMatch!.start,
+            _scanner.lastMatch!.end,
           ));
         }
       }
@@ -346,13 +346,13 @@ class CodeSpan {
   CodeSpan({this.type = _HighlightType.base, this.text});
 
   final _HighlightType type;
-  final String text;
+  final String? text;
 
   @override
   String toString() {
     return 'TextSpan('
         'style: codeStyle.${_styleNameOf(type)}, '
-        "text: '${_escape(text)}'"
+        "text: '${_escape(text!)}'"
         ')';
   }
 }
@@ -376,7 +376,6 @@ String _styleNameOf(_HighlightType type) {
     case _HighlightType.base:
       return 'baseStyle';
   }
-  return '';
 }
 
 String _escape(String text) {
@@ -409,4 +408,4 @@ String _encode(int charCode) {
 String _encodeAndPad(int charCode) {
   final encoded = _encode(charCode);
   return '0' * (4 - encoded.length) + encoded;
-}
\ No newline at end of file
+}
diff --git a/example/tool/codeviewer_cli/segment_generator.dart b/example/tool/codeviewer_cli/segment_generator.dart
index e7bd35d..b45903d 100644
--- a/example/tool/codeviewer_cli/segment_generator.dart
+++ b/example/tool/codeviewer_cli/segment_generator.dart
@@ -4,6 +4,7 @@
 
 import 'dart:convert';
 import 'dart:io';
+
 import 'prehighlighter.dart';
 
 const _globalPrologue =
@@ -30,7 +31,7 @@ enum _FileReadStatus {
 
 /// Returns the new status of the scanner whose previous status was
 /// [oldStatus], after scanning the line [line].
-_FileReadStatus _updatedStatus(_FileReadStatus oldStatus, String line) {
+_FileReadStatus? _updatedStatus(_FileReadStatus? oldStatus, String line) {
   _FileReadStatus lineStatus;
   if (line.trim().startsWith('//')) {
     lineStatus = _FileReadStatus.comments;
@@ -40,7 +41,7 @@ _FileReadStatus _updatedStatus(_FileReadStatus oldStatus, String line) {
     lineStatus = _FileReadStatus.finished;
   }
 
-  _FileReadStatus newStatus;
+  _FileReadStatus? newStatus;
   switch (oldStatus) {
     case _FileReadStatus.comments:
       newStatus =
@@ -56,6 +57,8 @@ _FileReadStatus _updatedStatus(_FileReadStatus oldStatus, String line) {
     case _FileReadStatus.finished:
       newStatus = oldStatus;
       break;
+    default:
+      newStatus = oldStatus;
   }
   return newStatus;
 }
@@ -77,7 +80,7 @@ Map<String, String> _createSegments(String sourceDirectoryPath) {
     final content = file.readAsStringSync();
     final lines = const LineSplitter().convert(content);
 
-    var status = _FileReadStatus.comments;
+    _FileReadStatus? status = _FileReadStatus.comments;
 
     final prologue = StringBuffer();
 
@@ -135,7 +138,7 @@ Map<String, String> _createSegments(String sourceDirectoryPath) {
         // Simple line.
 
         for (final name in activeSubsegments) {
-          subsegments[name].writeln(line);
+          subsegments[name]!.writeln(line);
         }
       }
     }
@@ -146,7 +149,7 @@ Map<String, String> _createSegments(String sourceDirectoryPath) {
   }
 
   var segments = <String, List<TaggedString>>{};
-  var segmentPrologues = <String, String>{};
+  var segmentPrologues = <String, String?>{};
 
   // Sometimes a code segment is made up of subsegments. They are marked by
   // names with a "#" symbol in it, such as "bottomSheetDemoModal#1" and
@@ -168,7 +171,7 @@ Map<String, String> _createSegments(String sourceDirectoryPath) {
     if (!segments.containsKey(name)) {
       segments[name] = [];
     }
-    segments[name].add(
+    segments[name]!.add(
       TaggedString(
         text: value.toString(),
         order: order,
@@ -179,7 +182,7 @@ Map<String, String> _createSegments(String sourceDirectoryPath) {
   });
 
   segments.forEach((key, value) {
-    value.sort((ts1, ts2) => (ts1.order - ts2.order).sign.round());
+    value.sort((ts1, ts2) => (ts1.order! - ts2.order!).sign.round());
   });
 
   var answer = <String, String>{};
@@ -187,11 +190,11 @@ Map<String, String> _createSegments(String sourceDirectoryPath) {
   for (final name in segments.keys) {
     final buffer = StringBuffer();
 
-    buffer.write(segmentPrologues[name].trim());
+    buffer.write(segmentPrologues[name]!.trim());
     buffer.write('\n\n');
 
-    for (final ts in segments[name]) {
-      buffer.write(ts.text.trim());
+    for (final ts in segments[name]!) {
+      buffer.write(ts.text!.trim());
       buffer.write('\n\n');
     }
 
@@ -208,8 +211,8 @@ Map<String, String> _createSegments(String sourceDirectoryPath) {
 class TaggedString {
   TaggedString({this.text, this.order});
 
-  final String text;
-  final double order;
+  final String? text;
+  final double? order;
 }
 
 void _formatSegments(Map<String, String> segments, IOSink output) {
@@ -254,13 +257,15 @@ void _formatSegments(Map<String, String> segments, IOSink output) {
 ///
 /// The target file is overwritten.
 void writeSegments(
-    {String sourceDirectoryPath, String targetFilePath, bool isDryRun}) {
+    {required String sourceDirectoryPath,
+    String? targetFilePath,
+    required bool isDryRun}) {
   final segments = _createSegments(sourceDirectoryPath);
-  final output = isDryRun ? stdout : File(targetFilePath).openWrite();
+  final output = isDryRun ? stdout : File(targetFilePath!).openWrite();
   _formatSegments(segments, output);
 }
 
 class PreformatterException implements Exception {
   PreformatterException(this.cause);
   String cause;
-}
\ No newline at end of file
+}
diff --git a/example/tool/grind.dart b/example/tool/grind.dart
index cd2bc2f..825f1f2 100644
--- a/example/tool/grind.dart
+++ b/example/tool/grind.dart
@@ -63,7 +63,7 @@ Future<void> _runProcess(String executable, List<String> arguments) async {
 // Function to make sure we capture all of the stdout.
 // Reference: https://github.com/dart-lang/sdk/issues/31666
 Future<String> _startProcess(String executable,
-    {List<String> arguments = const [], String input}) async {
+    {List<String> arguments = const [], String? input}) async {
   final output = <int>[];
   final completer = Completer<int>();
   final process = await Process.start(executable, arguments);
diff --git a/pubspec.lock b/pubspec.lock
index 347e0bd..f99489e 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -10,88 +10,81 @@ packages:
       url: "https://git.oa00.com/flutter_pub/animated_collection.git"
     source: git
     version: "0.0.1"
-  animator:
-    dependency: transitive
-    description:
-      name: animator
-      url: "https://pub.flutter-io.cn"
-    source: hosted
-    version: "3.1.0"
   async:
     dependency: transitive
     description:
       name: async
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.5.0"
   auto_size_text_pk:
     dependency: transitive
     description:
       name: auto_size_text_pk
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "3.0.0"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.0"
   bot_toast:
     dependency: "direct main"
     description:
       name: bot_toast
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "4.0.1"
   characters:
     dependency: transitive
     description:
       name: characters
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.2.0"
   clock:
     dependency: transitive
     description:
       name: clock
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.15.0"
   cross_file:
     dependency: transitive
     description:
       name: cross_file
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.3.1+4"
   expandable:
     dependency: "direct main"
     description:
       name: expandable
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "5.0.1"
   fake_async:
     dependency: transitive
     description:
       name: fake_async
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.2.0"
   flutter:
@@ -103,21 +96,21 @@ packages:
     dependency: "direct main"
     description:
       name: flutter_easyrefresh
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.2.1"
   flutter_plugin_android_lifecycle:
     dependency: transitive
     description:
       name: flutter_plugin_android_lifecycle
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.2"
   flutter_screenutil:
     dependency: "direct main"
     description:
       name: flutter_screenutil
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "5.0.0+2"
   flutter_test:
@@ -134,98 +127,98 @@ packages:
     dependency: "direct main"
     description:
       name: get
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.1.4"
+    version: "4.3.8"
   http:
     dependency: transitive
     description:
       name: http
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.13.3"
   http_parser:
     dependency: transitive
     description:
       name: http_parser
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "4.0.0"
   image_picker:
     dependency: "direct main"
     description:
       name: image_picker
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.7.5+4"
   image_picker_for_web:
     dependency: transitive
     description:
       name: image_picker_for_web
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0"
+    version: "2.1.3"
   image_picker_platform_interface:
     dependency: transitive
     description:
       name: image_picker_platform_interface
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.0"
+    version: "2.3.0"
   intl:
     dependency: transitive
     description:
       name: intl
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.17.0"
   js:
     dependency: transitive
     description:
       name: js
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.6.3"
   lpinyin:
     dependency: "direct main"
     description:
       name: lpinyin
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.3"
   matcher:
     dependency: transitive
     description:
       name: matcher
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0"
   pedantic:
     dependency: transitive
     description:
       name: pedantic
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.11.1"
   plugin_platform_interface:
     dependency: transitive
     description:
       name: plugin_platform_interface
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.1"
   sky_engine:
@@ -237,77 +230,70 @@ packages:
     dependency: transitive
     description:
       name: source_span
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.10.0"
-  states_rebuilder:
-    dependency: transitive
-    description:
-      name: states_rebuilder
-      url: "https://pub.flutter-io.cn"
-    source: hosted
-    version: "4.3.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "0.2.19"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.0"
   velocity_x:
     dependency: "direct main"
     description:
       name: velocity_x
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.6.1"
+    version: "3.3.0"
   vxstate:
     dependency: transitive
     description:
       name: vxstate
-      url: "https://pub.flutter-io.cn"
+      url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.0"
 sdks:
diff --git a/pubspec.yaml b/pubspec.yaml
index 2079115..f4fd850 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -16,7 +16,7 @@ dependencies:
   lpinyin: ^2.0.1
   image_picker: ^0.7.2
   bot_toast: ^4.0.0+1
-  velocity_x: ^2.6.1
+  velocity_x: ^3.3.0
   expandable: ^5.0.1
   animated_collection:
     git: