diff --git a/example/pubspec.lock b/example/pubspec.lock
index 76cd661..d07fd5f 100644
--- a/example/pubspec.lock
+++ b/example/pubspec.lock
@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.9.0"
+    version: "2.8.1"
   boolean_selector:
     dependency: transitive
     description:
@@ -21,21 +21,28 @@ packages:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.1"
+    version: "1.1.0"
+  charcode:
+    dependency: transitive
+    description:
+      name: charcode
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.3.1"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.16.0"
+    version: "1.15.0"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -49,7 +56,7 @@ packages:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.1"
+    version: "1.2.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -66,21 +73,14 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.12"
-  material_color_utilities:
-    dependency: transitive
-    description:
-      name: material_color_utilities
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.1.5"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0"
+    version: "1.7.0"
   multi_select_flutter:
     dependency: "direct main"
     description:
@@ -94,7 +94,7 @@ packages:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.2"
+    version: "1.8.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -106,7 +106,7 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.0"
+    version: "1.8.1"
   stack_trace:
     dependency: transitive
     description:
@@ -127,27 +127,34 @@ packages:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.1"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.4.12"
+    version: "0.4.2"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.2"
+    version: "2.1.0"
 sdks:
-  dart: ">=2.17.0-0 <3.0.0"
+  dart: ">=2.12.0 <3.0.0"
diff --git a/lib/bottom_sheet/multi_select_bottom_sheet_field.dart b/lib/bottom_sheet/multi_select_bottom_sheet_field.dart
index ff11320..a8215e8 100644
--- a/lib/bottom_sheet/multi_select_bottom_sheet_field.dart
+++ b/lib/bottom_sheet/multi_select_bottom_sheet_field.dart
@@ -327,7 +327,7 @@ class __MultiSelectBottomSheetFieldViewState<V>
       _selectedItems = [];
       _selectedItems.addAll(widget.initialValue);
 
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance?.addPostFrameCallback((_) {
         widget.state!.didChange(_selectedItems);
       });
     }
diff --git a/lib/chip_display/multi_select_chip_display.dart b/lib/chip_display/multi_select_chip_display.dart
index b5a3583..0d70e19 100644
--- a/lib/chip_display/multi_select_chip_display.dart
+++ b/lib/chip_display/multi_select_chip_display.dart
@@ -96,7 +96,7 @@ class MultiSelectChipDisplay<V> extends StatelessWidget {
               height: height ?? MediaQuery.of(context).size.height * 0.08,
               child: scrollBar != null
                   ? Scrollbar(
-                      thumbVisibility: scrollBar!.isAlwaysShown,
+                      // thumbVisibility: scrollBar!.isAlwaysShown,
                       controller: _scrollController,
                       child: ListView.builder(
                         controller: _scrollController,
diff --git a/lib/chip_field/multi_select_chip_field.dart b/lib/chip_field/multi_select_chip_field.dart
index 35865b5..978d8be 100644
--- a/lib/chip_field/multi_select_chip_field.dart
+++ b/lib/chip_field/multi_select_chip_field.dart
@@ -269,7 +269,7 @@ class __MultiSelectChipFieldViewState<V>
     _selectedValues.addAll(widget.initialValue);
 
     if (widget.scrollControl != null && widget.scroll)
-      WidgetsBinding.instance.addPostFrameCallback((_) => _scrollToPosition());
+      WidgetsBinding.instance?.addPostFrameCallback((_) => _scrollToPosition());
   }
 
   @override
@@ -280,7 +280,7 @@ class __MultiSelectChipFieldViewState<V>
       _selectedValues = [];
       _selectedValues.addAll(widget.initialValue);
 
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance?.addPostFrameCallback((_) {
         widget.state!.didChange(_selectedValues);
       });
     }
@@ -395,7 +395,7 @@ class __MultiSelectChipFieldViewState<V>
                           MediaQuery.of(context).size.height * 0.08,
                       child: widget.scrollBar != null
                           ? Scrollbar(
-                              thumbVisibility: widget.scrollBar!.isAlwaysShown,
+                              // thumbVisibility: widget.scrollBar!.isAlwaysShown,
                               controller: _scrollController,
                               child: ListView.builder(
                                 controller: _scrollController,
diff --git a/lib/dialog/multi_select_dialog_field.dart b/lib/dialog/multi_select_dialog_field.dart
index b229a4d..902c2d7 100644
--- a/lib/dialog/multi_select_dialog_field.dart
+++ b/lib/dialog/multi_select_dialog_field.dart
@@ -310,7 +310,7 @@ class __MultiSelectDialogFieldViewState<V>
       _selectedItems = [];
       _selectedItems.addAll(widget.initialValue);
 
-      WidgetsBinding.instance.addPostFrameCallback((_) {
+      WidgetsBinding.instance?.addPostFrameCallback((_) {
         widget.state!.didChange(_selectedItems);
       });
     }
diff --git a/pubspec.lock b/pubspec.lock
index 8a01ee3..2de0702 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.9.0"
+    version: "2.8.1"
   boolean_selector:
     dependency: transitive
     description:
@@ -21,28 +21,35 @@ packages:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.1"
+    version: "1.1.0"
+  charcode:
+    dependency: transitive
+    description:
+      name: charcode
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.3.1"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.0"
   collection:
     dependency: "direct main"
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.16.0"
+    version: "1.15.0"
   fake_async:
     dependency: transitive
     description:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.1"
+    version: "1.2.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -59,28 +66,21 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.12"
-  material_color_utilities:
-    dependency: transitive
-    description:
-      name: material_color_utilities
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.1.5"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0"
+    version: "1.7.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.2"
+    version: "1.8.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -92,7 +92,7 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.0"
+    version: "1.8.1"
   stack_trace:
     dependency: transitive
     description:
@@ -113,27 +113,34 @@ packages:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.1"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.4.12"
+    version: "0.4.2"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.2"
+    version: "2.1.0"
 sdks:
-  dart: ">=2.17.0-0 <3.0.0"
+  dart: ">=2.12.0 <3.0.0"