diff --git a/dev/integration_tests/android_semantics_testing/lib/main.dart b/dev/integration_tests/android_semantics_testing/lib/main.dart
index 12afeada564..3e8002ba233 100644
--- a/dev/integration_tests/android_semantics_testing/lib/main.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/main.dart
@@ -23,11 +23,11 @@ void main() {
 
 const MethodChannel kSemanticsChannel = MethodChannel('semantics');
 
-Future<String> dataHandler(String? message) async {
-  if (message != null && message.contains('getSemanticsNode')) {
+Future<String> dataHandler(String message) async {
+  if (message.contains('getSemanticsNode')) {
     final Completer<String> completer = Completer<String>();
     final int id = int.tryParse(message.split('#')[1]) ?? 0;
-    Future<void> completeSemantics([Object? _]) async {
+    Future<void> completeSemantics([Object _]) async {
       final dynamic result = await kSemanticsChannel.invokeMethod<dynamic>('getSemanticsNode', <String, dynamic>{
         'id': id,
       });
@@ -40,10 +40,10 @@ Future<String> dataHandler(String? message) async {
     }
     return completer.future;
   }
-  if (message != null && message.contains('setClipboard')) {
+  if (message.contains('setClipboard')) {
     final Completer<String> completer = Completer<String>();
     final String str = message.split('#')[1];
-    Future<void> completeSetClipboard([Object? _]) async {
+    Future<void> completeSetClipboard([Object _]) async {
       await kSemanticsChannel.invokeMethod<dynamic>('setClipboard', <String, dynamic>{
         'message': str,
       });
@@ -67,7 +67,7 @@ Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
 };
 
 class TestApp extends StatelessWidget {
-  const TestApp({super.key});
+  const TestApp({Key key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
diff --git a/dev/integration_tests/android_semantics_testing/lib/src/common.dart b/dev/integration_tests/android_semantics_testing/lib/src/common.dart
index 205a0a49e48..9305855f495 100644
--- a/dev/integration_tests/android_semantics_testing/lib/src/common.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/src/common.dart
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// ignore_for_file: avoid_dynamic_calls
-
 import 'dart:convert';
 
 import 'package:meta/meta.dart';
@@ -55,13 +53,13 @@ class AndroidSemanticsNode {
   ///       ]
   ///     }
   factory AndroidSemanticsNode.deserialize(String value) {
-    return AndroidSemanticsNode._(json.decode(value));
+    return AndroidSemanticsNode._(json.decode(value) as Map<String, Object>);
   }
 
-  final dynamic _values;
+  final Map<String, Object> _values;
   final List<AndroidSemanticsNode> _children = <AndroidSemanticsNode>[];
 
-  dynamic get _flags => _values['flags'];
+  Map<String, Object> get _flags => _values['flags'] as Map<String, Object>;
 
   /// The text value of the semantics node.
   ///
@@ -134,12 +132,13 @@ class AndroidSemanticsNode {
 
   /// Gets a [Rect] which defines the position and size of the semantics node.
   Rect getRect() {
-    final dynamic rawRect = _values['rect'];
+    final Map<String, Object> rawRect = _values['rect'] as Map<String, Object>;
+    final Map<String, int> rect = rawRect.cast<String, int>();
     return Rect.fromLTRB(
-      (rawRect['left']! as int).toDouble(),
-      (rawRect['top']! as int).toDouble(),
-      (rawRect['right']! as int).toDouble(),
-      (rawRect['bottom']! as int).toDouble(),
+      rect['left'].toDouble(),
+      rect['top'].toDouble(),
+      rect['right'].toDouble(),
+      rect['bottom'].toDouble(),
     );
   }
 
@@ -151,7 +150,7 @@ class AndroidSemanticsNode {
 
   /// Gets a list of [AndroidSemanticsActions] which are defined for the node.
   List<AndroidSemanticsAction> getActions() => <AndroidSemanticsAction>[
-    for (final int id in (_values['actions']! as List<dynamic>).cast<int>()) AndroidSemanticsAction.deserialize(id)!,
+    for (final int id in (_values['actions'] as List<dynamic>).cast<int>()) AndroidSemanticsAction.deserialize(id),
   ];
 
   @override
diff --git a/dev/integration_tests/android_semantics_testing/lib/src/constants.dart b/dev/integration_tests/android_semantics_testing/lib/src/constants.dart
index ef8a863d9eb..22f75bc7bd6 100644
--- a/dev/integration_tests/android_semantics_testing/lib/src/constants.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/src/constants.dart
@@ -168,7 +168,7 @@ class AndroidSemanticsAction {
       case _kSetText:
         return 'AndroidSemanticsAction.setText';
       default:
-        throw UnimplementedError();
+        return null;
     }
   }
 
@@ -211,7 +211,7 @@ class AndroidSemanticsAction {
   /// Creates a new [AndroidSemanticsAction] from an integer `value`.
   ///
   /// Returns `null` if the id is not a known Android accessibility action.
-  static AndroidSemanticsAction? deserialize(int value) {
+  static AndroidSemanticsAction deserialize(int value) {
     return _kActionById[value];
   }
 }
diff --git a/dev/integration_tests/android_semantics_testing/lib/src/matcher.dart b/dev/integration_tests/android_semantics_testing/lib/src/matcher.dart
index 37155e668ac..ea36302266a 100644
--- a/dev/integration_tests/android_semantics_testing/lib/src/matcher.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/src/matcher.dart
@@ -18,24 +18,24 @@ import 'constants.dart';
 /// the Android accessibility bridge, and not the semantics object created by
 /// the Flutter framework.
 Matcher hasAndroidSemantics({
-  String? text,
-  String? contentDescription,
-  String? className,
-  int? id,
-  Rect? rect,
-  Size? size,
-  List<AndroidSemanticsAction>? actions,
-  List<AndroidSemanticsAction>? ignoredActions,
-  List<AndroidSemanticsNode>? children,
-  bool? isChecked,
-  bool? isCheckable,
-  bool? isEditable,
-  bool? isEnabled,
-  bool? isFocusable,
-  bool? isFocused,
-  bool? isHeading,
-  bool? isPassword,
-  bool? isLongClickable,
+  String text,
+  String contentDescription,
+  String className,
+  int id,
+  Rect rect,
+  Size size,
+  List<AndroidSemanticsAction> actions,
+  List<AndroidSemanticsAction> ignoredActions,
+  List<AndroidSemanticsNode> children,
+  bool isChecked,
+  bool isCheckable,
+  bool isEditable,
+  bool isEnabled,
+  bool isFocusable,
+  bool isFocused,
+  bool isHeading,
+  bool isPassword,
+  bool isLongClickable,
 }) {
   return _AndroidSemanticsMatcher(
     text: text,
@@ -79,23 +79,23 @@ class _AndroidSemanticsMatcher extends Matcher {
     this.isLongClickable,
   });
 
-  final String? text;
-  final String? className;
-  final String? contentDescription;
-  final int? id;
-  final List<AndroidSemanticsAction>? actions;
-  final List<AndroidSemanticsAction>? ignoredActions;
-  final Rect? rect;
-  final Size? size;
-  final bool? isChecked;
-  final bool? isCheckable;
-  final bool? isEditable;
-  final bool? isEnabled;
-  final bool? isFocusable;
-  final bool? isFocused;
-  final bool? isHeading;
-  final bool? isPassword;
-  final bool? isLongClickable;
+  final String text;
+  final String className;
+  final String contentDescription;
+  final int id;
+  final List<AndroidSemanticsAction> actions;
+  final List<AndroidSemanticsAction> ignoredActions;
+  final Rect rect;
+  final Size size;
+  final bool isChecked;
+  final bool isCheckable;
+  final bool isEditable;
+  final bool isEnabled;
+  final bool isFocusable;
+  final bool isFocused;
+  final bool isHeading;
+  final bool isPassword;
+  final bool isLongClickable;
 
   @override
   Description describe(Description description) {
@@ -149,7 +149,7 @@ class _AndroidSemanticsMatcher extends Matcher {
   }
 
   @override
-  bool matches(covariant AndroidSemanticsNode item, Map<dynamic, dynamic> matchState) {
+  bool matches(covariant AndroidSemanticsNode item, Map<Object, Object> matchState) {
     if (text != null && text != item.text) {
       return _failWithMessage('Expected text: $text', matchState);
     }
@@ -170,13 +170,13 @@ class _AndroidSemanticsMatcher extends Matcher {
     }
     if (actions != null) {
       final List<AndroidSemanticsAction> itemActions = item.getActions();
-      if (!unorderedEquals(actions!).matches(itemActions, matchState)) {
-        final List<String> actionsString = actions!.map<String>((AndroidSemanticsAction action) => action.toString()).toList()..sort();
+      if (!unorderedEquals(actions).matches(itemActions, matchState)) {
+        final List<String> actionsString = actions.map<String>((AndroidSemanticsAction action) => action.toString()).toList()..sort();
         final List<String> itemActionsString = itemActions.map<String>((AndroidSemanticsAction action) => action.toString()).toList()..sort();
-        final Set<AndroidSemanticsAction> unexpected = itemActions.toSet().difference(actions!.toSet());
+        final Set<AndroidSemanticsAction> unexpected = itemActions.toSet().difference(actions.toSet());
         final Set<String> unexpectedInString = itemActionsString.toSet().difference(actionsString.toSet());
         final Set<String> missingInString = actionsString.toSet().difference(itemActionsString.toSet());
-        if (missingInString.isEmpty && ignoredActions != null && unexpected.every(ignoredActions!.contains)) {
+        if (missingInString.isEmpty && ignoredActions != null && unexpected.every(ignoredActions.contains)) {
           return true;
         }
         return _failWithMessage('Expected actions: $actionsString\nActual actions: $itemActionsString\nUnexpected: $unexpectedInString\nMissing: $missingInString', matchState);
@@ -214,8 +214,8 @@ class _AndroidSemanticsMatcher extends Matcher {
   }
 
   @override
-  Description describeMismatch(dynamic item, Description mismatchDescription,
-      Map<dynamic, dynamic> matchState, bool verbose) {
+  Description describeMismatch(Object item, Description mismatchDescription,
+      Map<Object, Object> matchState, bool verbose) {
     return mismatchDescription.add(matchState['failure'] as String);
   }
 
diff --git a/dev/integration_tests/android_semantics_testing/lib/src/tests/controls_page.dart b/dev/integration_tests/android_semantics_testing/lib/src/tests/controls_page.dart
index fad7ff4ebaf..3d4cda7e572 100644
--- a/dev/integration_tests/android_semantics_testing/lib/src/tests/controls_page.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/src/tests/controls_page.dart
@@ -9,7 +9,7 @@ export 'controls_constants.dart';
 
 /// A test page with a checkbox, three radio buttons, and a switch.
 class SelectionControlsPage extends StatefulWidget {
-  const SelectionControlsPage({super.key});
+  const SelectionControlsPage({Key key}) : super(key: key);
 
   @override
   State<StatefulWidget> createState() => _SelectionControlsPageState();
@@ -28,15 +28,15 @@ class _SelectionControlsPageState extends State<SelectionControlsPage> {
   bool _isLabeledOn = false;
   int _radio = 0;
 
-  void _updateCheckbox(bool? newValue) {
+  void _updateCheckbox(bool newValue) {
     setState(() {
-      _isChecked = newValue!;
+      _isChecked = newValue;
     });
   }
 
-  void _updateRadio(int? newValue) {
+  void _updateRadio(int newValue) {
     setState(() {
-      _radio = newValue!;
+      _radio = newValue;
     });
   }
 
diff --git a/dev/integration_tests/android_semantics_testing/lib/src/tests/headings_page.dart b/dev/integration_tests/android_semantics_testing/lib/src/tests/headings_page.dart
index a4ccf0b7489..b08ebdbbe41 100644
--- a/dev/integration_tests/android_semantics_testing/lib/src/tests/headings_page.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/src/tests/headings_page.dart
@@ -9,7 +9,7 @@ export 'headings_constants.dart';
 
 /// A test page with an app bar and some body text for testing heading flags.
 class HeadingsPage extends StatelessWidget {
-  const HeadingsPage({super.key});
+  const HeadingsPage({Key key}) : super(key: key);
 
   static const ValueKey<String> _appBarTitleKey = ValueKey<String>(appBarTitleKeyValue);
   static const ValueKey<String> _bodyTextKey = ValueKey<String>(bodyTextKeyValue);
diff --git a/dev/integration_tests/android_semantics_testing/lib/src/tests/popup_page.dart b/dev/integration_tests/android_semantics_testing/lib/src/tests/popup_page.dart
index 3ede08eac3b..6f0b064fc02 100644
--- a/dev/integration_tests/android_semantics_testing/lib/src/tests/popup_page.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/src/tests/popup_page.dart
@@ -10,7 +10,7 @@ export 'popup_constants.dart';
 
 /// A page with a popup menu, a dropdown menu, and a modal alert.
 class PopupControlsPage extends StatefulWidget {
-  const PopupControlsPage({super.key});
+  const PopupControlsPage({Key key}) : super(key: key);
 
   @override
   State<StatefulWidget> createState() => _PopupControlsPageState();
@@ -60,9 +60,9 @@ class _PopupControlsPageState extends State<PopupControlsPage> {
                     child: Text(item),
                   );
                 }).toList(),
-                onChanged: (String? value) {
+                onChanged: (String value) {
                   setState(() {
-                    dropdownValue = value!;
+                    dropdownValue = value;
                   });
                 },
               ),
diff --git a/dev/integration_tests/android_semantics_testing/lib/src/tests/text_field_page.dart b/dev/integration_tests/android_semantics_testing/lib/src/tests/text_field_page.dart
index fcd6368c0bc..20a22449aa2 100644
--- a/dev/integration_tests/android_semantics_testing/lib/src/tests/text_field_page.dart
+++ b/dev/integration_tests/android_semantics_testing/lib/src/tests/text_field_page.dart
@@ -10,7 +10,7 @@ export 'text_field_constants.dart';
 
 /// A page with a normal text field and a password field.
 class TextFieldPage extends StatefulWidget {
-  const TextFieldPage({super.key});
+  const TextFieldPage({Key key}) : super(key: key);
 
   @override
   State<StatefulWidget> createState() => _TextFieldPageState();
diff --git a/dev/integration_tests/android_semantics_testing/pubspec.yaml b/dev/integration_tests/android_semantics_testing/pubspec.yaml
index 417b4ce1abc..4801d409fc1 100644
--- a/dev/integration_tests/android_semantics_testing/pubspec.yaml
+++ b/dev/integration_tests/android_semantics_testing/pubspec.yaml
@@ -1,7 +1,7 @@
 name: android_semantics_testing
 description: Integration testing library for Android semantics
 environment:
-  sdk: '>=2.17.0-0 <3.0.0'
+  sdk: '>=2.9.0 <3.0.0'
 
 dependencies:
   flutter:
diff --git a/dev/integration_tests/android_semantics_testing/test_driver/main_test.dart b/dev/integration_tests/android_semantics_testing/test_driver/main_test.dart
index df0f14f263d..e4faad917f1 100644
--- a/dev/integration_tests/android_semantics_testing/test_driver/main_test.dart
+++ b/dev/integration_tests/android_semantics_testing/test_driver/main_test.dart
@@ -20,7 +20,7 @@ const List<AndroidSemanticsAction> ignoredAccessibilityFocusActions = <AndroidSe
 ];
 
 String adbPath() {
-  final String androidHome = io.Platform.environment['ANDROID_HOME'] ?? io.Platform.environment['ANDROID_SDK_ROOT']!;
+  final String androidHome = io.Platform.environment['ANDROID_HOME'] ?? io.Platform.environment['ANDROID_SDK_ROOT'];
   if (androidHome == null) {
     return 'adb';
   } else {
@@ -30,7 +30,7 @@ String adbPath() {
 
 void main() {
   group('AccessibilityBridge', () {
-    late FlutterDriver driver;
+    FlutterDriver driver;
     Future<AndroidSemanticsNode> getSemantics(SerializableFinder finder) async {
       final int id = await driver.getSemanticsId(finder);
       final String data = await driver.requestData('getSemanticsNode#$id');
@@ -38,7 +38,7 @@ void main() {
     }
 
     // The version of TalkBack running on the device.
-    Version? talkbackVersion;
+    Version talkbackVersion;
 
     Future<Version> getTalkbackVersion() async {
       final io.ProcessResult result = await io.Process.run(adbPath(), const <String>[
@@ -51,7 +51,7 @@ void main() {
         throw Exception('Failed to get TalkBack version: ${result.stdout as String}\n${result.stderr as String}');
       }
       final List<String> lines = (result.stdout as String).split('\n');
-      String? version;
+      String version;
       for (final String line in lines) {
         if (line.contains('versionName')) {
           version = line.replaceAll(RegExp(r'\s*versionName='), '');
@@ -64,14 +64,14 @@ void main() {
 
       // Android doesn't quite use semver, so convert the version string to semver form.
       final RegExp startVersion = RegExp(r'(?<major>\d+)\.(?<minor>\d+)\.(?<patch>\d+)(\.(?<build>\d+))?');
-      final RegExpMatch? match = startVersion.firstMatch(version);
+      final RegExpMatch match = startVersion.firstMatch(version);
       if (match == null) {
         return Version(0, 0, 0);
       }
       return Version(
-        int.parse(match.namedGroup('major')!),
-        int.parse(match.namedGroup('minor')!),
-        int.parse(match.namedGroup('patch')!),
+        int.parse(match.namedGroup('major')),
+        int.parse(match.namedGroup('minor')),
+        int.parse(match.namedGroup('patch')),
         build: match.namedGroup('build'),
       );
     }
@@ -104,7 +104,7 @@ void main() {
         'null',
       ]);
       await run.exitCode;
-      driver.close();
+      driver?.close();
     });
 
     group('TextField', () {