diff --git a/example/lib/hook_example.dart b/example/lib/hook_example.dart
index 7fa25810e..321e3e987 100644
--- a/example/lib/hook_example.dart
+++ b/example/lib/hook_example.dart
@@ -333,7 +333,7 @@ class AddDemo {
 
   @Add("package:example/receiver_test.dart", "Receiver")
   @pragma("vm:entry-point")
-  dynamic addTest(PointCut pointCut, int j, {String s, int i}) {
+  dynamic addTest(PointCut pointCut, int j, {String? s, int? i}) {
     print('[beike_aspectd]: Add method');
   }
 
diff --git a/example/lib/main.dart b/example/lib/main.dart
index 58e341b4e..cf2eb4bcb 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -69,7 +69,7 @@ class MyApp extends StatelessWidget {
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({Key key, this.title}) : super(key: key);
+  MyHomePage({Key? key, this.title}) : super(key: key);
 
   // This widget is the home page of your application. It is stateful, meaning
   // that it has a State object (defined below) that contains fields that affect
@@ -80,16 +80,16 @@ class MyHomePage extends StatefulWidget {
   // used by the build method of the State. Fields in a Widget subclass are
   // always marked "final".
 
-  final String title;
+  final String? title;
 
   @override
   _MyHomePageState createState() => _MyHomePageState(i: 19);
 }
 
 class TextRightImageModel {
-  String showName;
+  String? showName;
 
-  String rightIcon;
+  String? rightIcon;
 
   Widget showCardWidget(BuildContext context) {
     return Container(
@@ -153,7 +153,7 @@ class _MyHomePageState extends State<MyHomePage> {
       appBar: AppBar(
         // Here we take the value from the MyHomePage object that was created by
         // the App.build method, and use it to set our appbar title.
-        title: Text(widget.title),
+        title: Text(widget.title??''),
       ),
       body: Center(
         // Center is a layout widget. It takes a single child and positions it
diff --git a/example/lib/receiver_test.dart b/example/lib/receiver_test.dart
index fc6fc405a..a8095e926 100644
--- a/example/lib/receiver_test.dart
+++ b/example/lib/receiver_test.dart
@@ -1,4 +1,3 @@
-// @dart=2.10
 
 class Receiver {
 
@@ -10,7 +9,7 @@ class Receiver {
     
   }
 
-   void receiveTapped(int i, {int j}) {
+   void receiveTapped(int i, {int? j}) {
     print('[KWLM]:onPluginDemo111 Called!');
   }
 }
diff --git a/example/pubspec.yaml b/example/pubspec.yaml
index 28a077e16..0a4de7c6e 100644
--- a/example/pubspec.yaml
+++ b/example/pubspec.yaml
@@ -14,7 +14,7 @@ description: A new Flutter application.
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter:
diff --git a/inner/flutter_frontend_server/frontend_server.dart.snapshot b/inner/flutter_frontend_server/frontend_server.dart.snapshot
index d91fe2f76..cd2983114 100644
Binary files a/inner/flutter_frontend_server/frontend_server.dart.snapshot and b/inner/flutter_frontend_server/frontend_server.dart.snapshot differ
diff --git a/inner/snapshot.dart b/inner/snapshot.dart
index 4e1837a96..f30b8008d 100644
--- a/inner/snapshot.dart
+++ b/inner/snapshot.dart
@@ -1,22 +1,41 @@
 import 'dart:io';
 
 void main(List<String> args) async {
-
   final String dartPath = Platform.executable;
 
-  List<String> command = <String>['--snapshot=../lib/bin/starter.snapshot', 'tool/starter.dart'];
+  List<String> command = <String>[
+    '--snapshot=../lib/bin/starter.snapshot',
+    'tool/starter.dart'
+  ];
+
+  print('Start generating starter.snapshot...');
+  Process result = await Process.start(dartPath, command);
+
+  stdout.addStream(result.stdout);
+  stderr.addStream(result.stderr);
+
+  if (await result.exitCode == 0) {
+    print('Generated starter.snapshot successfully!');
+  } else {
+    print('Failed t0 generate starter.snapshot!');
+  }
 
+  command = <String>[
+    '--deterministic',
+    '--snapshot=flutter_frontend_server/frontend_server.dart.snapshot',
+    'flutter_frontend_server/starter.dart'
+  ];
 
-  Process result = await Process.start(
-    dartPath,
-    command
+  print('Start generating frontend_server.dart.snapshot...');
 
-  );
+  result = await Process.start(dartPath, command);
 
-  command = <String>['--deterministic', '--snapshot=flutter_frontend_server/frontend_server.dart.snapshot', 'flutter_frontend_server/starter.dart'];
+  if (await result.exitCode == 0) {
+    print('Generated frontend_server.dart.snapshot successfully!');
+  } else {
+    print('Failed t0 generate frontend_server.dart.snapshot!');
+  }
 
-  result = await Process.start(
-      dartPath,
-      command
-  );
-}
\ No newline at end of file
+  stdout.addStream(result.stdout);
+  stderr.addStream(result.stderr);
+}
diff --git a/lib/aspectd.dart b/lib/aspectd.dart
index 430b4c6e9..56bf195d6 100644
--- a/lib/aspectd.dart
+++ b/lib/aspectd.dart
@@ -1,3 +1 @@
-// @dart=2.8
-
 export 'package:beike_aspectd/src/plugins/aop/aop.dart';
diff --git a/lib/bin/starter.snapshot b/lib/bin/starter.snapshot
index 87905d516..d630e97d9 100644
Binary files a/lib/bin/starter.snapshot and b/lib/bin/starter.snapshot differ
diff --git a/lib/src/plugins/aop/annotation/annotation_info.dart b/lib/src/plugins/aop/annotation/annotation_info.dart
index 7f95b6cec..873ad98f9 100644
--- a/lib/src/plugins/aop/annotation/annotation_info.dart
+++ b/lib/src/plugins/aop/annotation/annotation_info.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 /// Indicating which (library, cls, method) pair to operate on.
 @pragma('vm:entry-point')
 class AnnotationInfo {
@@ -14,23 +12,23 @@ class AnnotationInfo {
       this.superCls,});
 
   /// Indicating which dart file to operate on.
-  final String importUri;
+  final String? importUri;
 
   /// Indicating which dart class to operate on.
-  final String clsName;
+  final String? clsName;
 
   /// Indicating which dart method to operate on.
-  final String methodName;
+  final String? methodName;
 
   /// Indicating whether those specification above should be regarded as
   /// regex expressions.
-  final bool isRegex;
+  final bool? isRegex;
 
   /// Indicating which line to operate on.
   /// This is only meaningful for inject grammar.
-  final int lineNum; //Line Number to insert at(Before), 1 based.
+  final int? lineNum; //Line Number to insert at(Before), 1 based.
 
   /// Indicating which classes inherited from the superCls to operate on.
   /// This is only meaningful for regex add grammer.
-  final String superCls;
+  final String? superCls;
 }
diff --git a/lib/src/plugins/aop/annotation/call.dart b/lib/src/plugins/aop/annotation/call.dart
index 2ba514fb3..cdfebec87 100644
--- a/lib/src/plugins/aop/annotation/call.dart
+++ b/lib/src/plugins/aop/annotation/call.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 import 'annotation_info.dart';
 
 /// Call grammar is working on those callsites for the annotated method.
@@ -11,7 +9,7 @@ class Call extends AnnotationInfo {
 
   @pragma('vm:entry-point')
   const Call._(String importUri, String clsName, String methodName,
-      {bool isRegex,this.excludeCoreLib})
+      {bool? isRegex,this.excludeCoreLib})
       : super(
             importUri: importUri,
             clsName: clsName,
@@ -19,6 +17,6 @@ class Call extends AnnotationInfo {
             isRegex: isRegex);
 
   /// Indicate whether to exclude flutter libs
-  final bool excludeCoreLib;
+  final bool? excludeCoreLib;
 
 }
diff --git a/lib/src/plugins/aop/annotation/execute.dart b/lib/src/plugins/aop/annotation/execute.dart
index 785ef2a16..933985e12 100644
--- a/lib/src/plugins/aop/annotation/execute.dart
+++ b/lib/src/plugins/aop/annotation/execute.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 import 'annotation_info.dart';
 
 /// Execute grammar is working on method body.
@@ -13,7 +11,7 @@ class Execute extends AnnotationInfo {
 
   @pragma('vm:entry-point')
   const Execute._(String importUri, String clsName, String methodName,
-      {bool isRegex})
+      {bool? isRegex})
       : super(
             importUri: importUri,
             clsName: clsName,
diff --git a/lib/src/plugins/aop/annotation/inject.dart b/lib/src/plugins/aop/annotation/inject.dart
index 749ab29c0..fa103bd71 100644
--- a/lib/src/plugins/aop/annotation/inject.dart
+++ b/lib/src/plugins/aop/annotation/inject.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 import 'annotation_info.dart';
 
 /// Inject grammar can help you to inject statements into specific method
@@ -12,7 +10,7 @@ class Inject extends AnnotationInfo {
 
   @pragma('vm:entry-point')
   const Inject._(String importUri, String clsName, String methodName,
-      {int lineNum, bool isRegex})
+      {int? lineNum, bool? isRegex})
       : super(
             importUri: importUri,
             clsName: clsName,
diff --git a/lib/src/plugins/aop/annotation/pointcut.dart b/lib/src/plugins/aop/annotation/pointcut.dart
index 8a3a57fbd..de0c14203 100644
--- a/lib/src/plugins/aop/annotation/pointcut.dart
+++ b/lib/src/plugins/aop/annotation/pointcut.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 /// Object carrying callsite information and methods which can enable you to
 /// call the original implementation.
 @pragma('vm:entry-point')
@@ -14,35 +12,35 @@ class PointCut {
   }
 
   /// Source infomation like file, linenum, etc for a call.
-  final Map<dynamic, dynamic> sourceInfos;
+  final Map<dynamic, dynamic>? sourceInfos;
 
   /// Target where a call is operating on, like x for x.foo().
-  final Object target;
+  final Object? target;
 
   /// Function name for a call, like foo for x.foo().
-  final String function;
+  final String? function;
 
   /// Unique key which can help the proceed function to distinguish a
   /// mocked call.
-  final String stubKey;
+  final String? stubKey;
 
   /// Positional parameters for a call.
-  final List<dynamic> positionalParams;
+  final List<dynamic>? positionalParams;
 
   /// Named parameters for a call.
-  final Map<dynamic, dynamic> namedParams;
+  final Map<dynamic, dynamic>? namedParams;
 
   /// Class's members. In Call mode, it's caller class's members. In execute mode,  it's execution class's members.
-  final Map<dynamic, dynamic> members;
+  final Map<dynamic, dynamic>? members;
 
   /// Class's annotations. In Call mode, it's caller class's annotations. In execute mode,  it's execution class's annotations.
-  final Map<dynamic, dynamic> annotations;
+  final Map<dynamic, dynamic>? annotations;
 
   /// Unified entrypoint to call a original method,
   /// the method body is generated dynamically when being transformed in
   /// compile time.
   @pragma('vm:entry-point')
-  Object proceed() {
+  Object? proceed() {
     return null;
   }
 }
diff --git a/lib/src/plugins/aop/aop.dart b/lib/src/plugins/aop/aop.dart
index bf86649dd..7a450b24d 100644
--- a/lib/src/plugins/aop/aop.dart
+++ b/lib/src/plugins/aop/aop.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 export 'annotation/aspect.dart';
 export 'annotation/call.dart';
 export 'annotation/execute.dart';
diff --git a/lib/src/plugins/aop/beike_annotation/add.dart b/lib/src/plugins/aop/beike_annotation/add.dart
index 7c85a13f5..cc55080e9 100644
--- a/lib/src/plugins/aop/beike_annotation/add.dart
+++ b/lib/src/plugins/aop/beike_annotation/add.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 import '../annotation/annotation_info.dart';
 
 /// Call grammar is working on those callsites for the annotated method.
@@ -11,7 +9,7 @@ class Add extends AnnotationInfo {
 
   @pragma('vm:entry-point')
   const Add._(String importUri, String clsName,
-      {bool isRegex, String superCls})
+      {bool? isRegex, String? superCls})
       : super(
             importUri: importUri,
             clsName: clsName,
diff --git a/lib/src/plugins/aop/beike_annotation/field_get.dart b/lib/src/plugins/aop/beike_annotation/field_get.dart
index b340e0377..c7024835a 100644
--- a/lib/src/plugins/aop/beike_annotation/field_get.dart
+++ b/lib/src/plugins/aop/beike_annotation/field_get.dart
@@ -1,5 +1,3 @@
-// @dart=2.8
-
 import '../annotation/annotation_info.dart';
 
 /// Field get grammar is working on those callsites for the annotated method.
@@ -11,7 +9,7 @@ class FieldGet extends AnnotationInfo {
 
   @pragma('vm:entry-point')
   const FieldGet._(String importUri, String clsName, this.fieldName, this.isStatic,
-      {bool isRegex})
+      {bool? isRegex})
       : super(
             importUri: importUri,
             clsName: clsName,
diff --git a/pubspec.yaml b/pubspec.yaml
index 66e33358b..d6940e801 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -13,7 +13,7 @@ homepage: https://github.com/LianjiaTech/Beike_AspectD.git
 # https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
 version: 1.0.1
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 dependencies:
   flutter:
     sdk: flutter