Moved the default BinaryMessenger instance to ServicesBinding (#38464)

* Moved the default BinaryMessenger instance to ServicesBinding

This reverts commit 821602aef3.

* Added assertion in defaultBinaryMessenger. Also fixed the devicelab tests.

dev/automated_tests/flutter_test/ticker_test.dart

@@ -11,6 +11,6 @@ void main() {
     Ticker((Duration duration) { })..start();
 
     final ByteData message = const StringCodec().encodeMessage('AppLifecycleState.paused');
-    await defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) {});
+    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) {});
   });
 }

dev/integration_tests/android_splash_screens/splash_screen_kitchen_sink/test_driver/main.dart

@@ -36,9 +36,9 @@ Future<String> respondToHostRequestForSplashLog(String _) {
 
 void createTestChannelBetweenAndroidAndFlutter() {
   // Channel used for Android to send Flutter changes to the splash display.
-  final BasicMessageChannel<String> testChannel = BasicMessageChannel<String>(
+  const BasicMessageChannel<String> testChannel = BasicMessageChannel<String>(
       'testChannel',
-      const StringCodec()
+      StringCodec()
   );
 
   // Every splash display change message that we receive from Android is either

dev/integration_tests/ios_add2app/flutterapp/lib/main.dart

@@ -25,6 +25,8 @@ const BasicMessageChannel<String> _kReloadChannel =
     BasicMessageChannel<String>(_kReloadChannelName, StringCodec());
 
 void main() {
+  // Ensures bindings are initialized before doing anything.
+  WidgetsFlutterBinding.ensureInitialized();
   // Start listening immediately for messages from the iOS side. ObjC calls
   // will be made to let us know when we should be changing the app state.
   _kReloadChannel.setMessageHandler(run);

examples/image_list/lib/main.dart

@@ -20,6 +20,8 @@ Future<void> main() async {
   final int port = httpServer.port;
   print('Listening on port $port.');
 
+  // Initializes bindings before using any platform channels.
+  WidgetsFlutterBinding.ensureInitialized();
   final ByteData byteData = await rootBundle.load('images/coast.jpg');
   final Uint8List bytes = byteData.buffer
       .asUint8List(byteData.offsetInBytes, byteData.lengthInBytes);

packages/flutter/lib/src/services/asset_bundle.dart

@@ -216,7 +216,7 @@ class PlatformAssetBundle extends CachingAssetBundle {
   Future<ByteData> load(String key) async {
     final Uint8List encoded = utf8.encoder.convert(Uri(path: Uri.encodeFull(key)).path);
     final ByteData asset =
-        await defaultBinaryMessenger.send('flutter/assets', encoded.buffer.asByteData());
+        await defaultBinaryMessenger.send('flutter/assets', encoded.buffer.asByteData()); // ignore: deprecated_member_use_from_same_package
     if (asset == null)
       throw FlutterError('Unable to load asset: $key');
     return asset;

packages/flutter/lib/src/services/binary_messenger.dart

@@ -7,6 +7,7 @@ import 'dart:typed_data';
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
+import 'binding.dart';
 
 /// A function which takes a platform message and asynchronously returns an encoded response.
 typedef MessageHandler = Future<ByteData> Function(ByteData message);
@@ -56,99 +57,32 @@ abstract class BinaryMessenger {
   void setMockMessageHandler(String channel, Future<ByteData> handler(ByteData message));
 }
 
-/// The default implementation of [BinaryMessenger].
-///
-/// This messenger sends messages from the app-side to the platform-side and
-/// dispatches incoming messages from the platform-side to the appropriate
-/// handler.
-class _DefaultBinaryMessenger extends BinaryMessenger {
-  const _DefaultBinaryMessenger._();
-
-  // Handlers for incoming messages from platform plugins.
-  // This is static so that this class can have a const constructor.
-  static final Map<String, MessageHandler> _handlers =
-      <String, MessageHandler>{};
-
-  // Mock handlers that intercept and respond to outgoing messages.
-  // This is static so that this class can have a const constructor.
-  static final Map<String, MessageHandler> _mockHandlers =
-      <String, MessageHandler>{};
-
-  Future<ByteData> _sendPlatformMessage(String channel, ByteData message) {
-    final Completer<ByteData> completer = Completer<ByteData>();
-    // ui.window is accessed directly instead of using ServicesBinding.instance.window
-    // because this method might be invoked before any binding is initialized.
-    // This issue was reported in #27541. It is not ideal to statically access
-    // ui.window because the Window may be dependency injected elsewhere with
-    // a different instance. However, static access at this location seems to be
-    // the least bad option.
-    ui.window.sendPlatformMessage(channel, message, (ByteData reply) {
-      try {
-        completer.complete(reply);
-      } catch (exception, stack) {
-        FlutterError.reportError(FlutterErrorDetails(
-          exception: exception,
-          stack: stack,
-          library: 'services library',
-          context: ErrorDescription('during a platform message response callback'),
-        ));
-      }
-    });
-    return completer.future;
-  }
-
-  @override
-  Future<void> handlePlatformMessage(
-    String channel,
-    ByteData data,
-    ui.PlatformMessageResponseCallback callback,
-  ) async {
-    ByteData response;
-    try {
-      final MessageHandler handler = _handlers[channel];
-      if (handler != null)
-        response = await handler(data);
-    } catch (exception, stack) {
-      FlutterError.reportError(FlutterErrorDetails(
-        exception: exception,
-        stack: stack,
-        library: 'services library',
-        context: ErrorDescription('during a platform message callback'),
-      ));
-    } finally {
-      callback(response);
-    }
-  }
-
-
-  @override
-  Future<ByteData> send(String channel, ByteData message) {
-    final MessageHandler handler = _mockHandlers[channel];
-    if (handler != null)
-      return handler(message);
-    return _sendPlatformMessage(channel, message);
-  }
-
-  @override
-  void setMessageHandler(String channel, MessageHandler handler) {
-    if (handler == null)
-      _handlers.remove(channel);
-    else
-      _handlers[channel] = handler;
-  }
-
-  @override
-  void setMockMessageHandler(String channel, MessageHandler handler) {
-    if (handler == null)
-      _mockHandlers.remove(channel);
-    else
-      _mockHandlers[channel] = handler;
-  }
-}
-
 /// The default instance of [BinaryMessenger].
 ///
+/// This API has been deprecated in favor of [ServicesBinding.defaultBinaryMessenger].
+/// Please use [ServicesBinding.defaultBinaryMessenger] as the default
+/// instance of [BinaryMessenger].
+///
 /// This is used to send messages from the application to the platform, and
 /// keeps track of which handlers have been registered on each channel so
 /// it may dispatch incoming messages to the registered handler.
-const BinaryMessenger defaultBinaryMessenger = _DefaultBinaryMessenger._();
+@Deprecated('Use ServicesBinding.instance.defaultBinaryMessenger instead.')
+BinaryMessenger get defaultBinaryMessenger {
+  assert(() {
+    if (ServicesBinding.instance == null) {
+      throw FlutterError(
+        'ServicesBinding.defaultBinaryMessenger was accessed before the '
+        'binding was initialized.\n'
+        'If you\'re running an application and need to access the binary '
+        'messenger before `runApp()` has been called (for example, during '
+        'plugin initialization), then you need to explicitly call the '
+        '`WidgetsFlutterBinding.ensureInitialized()` first.\n'
+        'If you\'re running a test, you can call the '
+        '`TestWidgetsFlutterBinding.ensureInitialized()` as the first line in '
+        'your test\'s `main()` method to initialize the binding.'
+      );
+    }
+    return true;
+  }());
+  return ServicesBinding.instance.defaultBinaryMessenger;
+}

packages/flutter/lib/src/services/binding.dart

@@ -3,6 +3,8 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:typed_data';
+import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
 
@@ -20,6 +22,7 @@ mixin ServicesBinding on BindingBase {
   void initInstances() {
     super.initInstances();
     _instance = this;
+    _defaultBinaryMessenger = createBinaryMessenger();
     window
       ..onPlatformMessage = defaultBinaryMessenger.handlePlatformMessage;
     initLicenses();
@@ -29,6 +32,21 @@ mixin ServicesBinding on BindingBase {
   static ServicesBinding get instance => _instance;
   static ServicesBinding _instance;
 
+  /// The default instance of [BinaryMessenger].
+  ///
+  /// This is used to send messages from the application to the platform, and
+  /// keeps track of which handlers have been registered on each channel so
+  /// it may dispatch incoming messages to the registered handler.
+  BinaryMessenger get defaultBinaryMessenger => _defaultBinaryMessenger;
+  BinaryMessenger _defaultBinaryMessenger;
+
+  /// Creates a default [BinaryMessenger] instance that can be used for sending
+  /// platform messages.
+  @protected
+  BinaryMessenger createBinaryMessenger() {
+    return const _DefaultBinaryMessenger._();
+  }
+
   /// Adds relevant licenses to the [LicenseRegistry].
   ///
   /// By default, the [ServicesBinding]'s implementation of [initLicenses] adds
@@ -117,3 +135,92 @@ mixin ServicesBinding on BindingBase {
     rootBundle.evict(asset);
   }
 }
+
+/// The default implementation of [BinaryMessenger].
+///
+/// This messenger sends messages from the app-side to the platform-side and
+/// dispatches incoming messages from the platform-side to the appropriate
+/// handler.
+class _DefaultBinaryMessenger extends BinaryMessenger {
+  const _DefaultBinaryMessenger._();
+
+  // Handlers for incoming messages from platform plugins.
+  // This is static so that this class can have a const constructor.
+  static final Map<String, MessageHandler> _handlers =
+      <String, MessageHandler>{};
+
+  // Mock handlers that intercept and respond to outgoing messages.
+  // This is static so that this class can have a const constructor.
+  static final Map<String, MessageHandler> _mockHandlers =
+      <String, MessageHandler>{};
+
+  Future<ByteData> _sendPlatformMessage(String channel, ByteData message) {
+    final Completer<ByteData> completer = Completer<ByteData>();
+    // ui.window is accessed directly instead of using ServicesBinding.instance.window
+    // because this method might be invoked before any binding is initialized.
+    // This issue was reported in #27541. It is not ideal to statically access
+    // ui.window because the Window may be dependency injected elsewhere with
+    // a different instance. However, static access at this location seems to be
+    // the least bad option.
+    ui.window.sendPlatformMessage(channel, message, (ByteData reply) {
+      try {
+        completer.complete(reply);
+      } catch (exception, stack) {
+        FlutterError.reportError(FlutterErrorDetails(
+          exception: exception,
+          stack: stack,
+          library: 'services library',
+          context: ErrorDescription('during a platform message response callback'),
+        ));
+      }
+    });
+    return completer.future;
+  }
+
+  @override
+  Future<void> handlePlatformMessage(
+    String channel,
+    ByteData data,
+    ui.PlatformMessageResponseCallback callback,
+  ) async {
+    ByteData response;
+    try {
+      final MessageHandler handler = _handlers[channel];
+      if (handler != null)
+        response = await handler(data);
+    } catch (exception, stack) {
+      FlutterError.reportError(FlutterErrorDetails(
+        exception: exception,
+        stack: stack,
+        library: 'services library',
+        context: ErrorDescription('during a platform message callback'),
+      ));
+    } finally {
+      callback(response);
+    }
+  }
+
+  @override
+  Future<ByteData> send(String channel, ByteData message) {
+    final MessageHandler handler = _mockHandlers[channel];
+    if (handler != null)
+      return handler(message);
+    return _sendPlatformMessage(channel, message);
+  }
+
+  @override
+  void setMessageHandler(String channel, MessageHandler handler) {
+    if (handler == null)
+      _handlers.remove(channel);
+    else
+      _handlers[channel] = handler;
+  }
+
+  @override
+  void setMockMessageHandler(String channel, MessageHandler handler) {
+    if (handler == null)
+      _mockHandlers.remove(channel);
+    else
+      _mockHandlers[channel] = handler;
+  }
+}

packages/flutter/lib/src/services/platform_channel.dart

@@ -8,6 +8,7 @@ import 'dart:typed_data';
 import 'package:flutter/foundation.dart';
 
 import 'binary_messenger.dart';
+import 'binding.dart';
 import 'message_codec.dart';
 import 'message_codecs.dart';
 
@@ -31,11 +32,12 @@ import 'message_codecs.dart';
 class BasicMessageChannel<T> {
   /// Creates a [BasicMessageChannel] with the specified [name], [codec] and [binaryMessenger].
   ///
-  /// None of [name], [codec], or [binaryMessenger] may be null.
-  const BasicMessageChannel(this.name, this.codec, { this.binaryMessenger = defaultBinaryMessenger })
-    : assert(name != null),
-      assert(codec != null),
-      assert(binaryMessenger != null);
+  /// The [name] and [codec] arguments cannot be null. The default [ServicesBinding.defaultBinaryMessenger]
+  /// instance is used if [binaryMessenger] is null.
+  const BasicMessageChannel(this.name, this.codec, { BinaryMessenger binaryMessenger })
+      : assert(name != null),
+        assert(codec != null),
+        _binaryMessenger = binaryMessenger;
 
   /// The logical channel on which communication happens, not null.
   final String name;
@@ -44,7 +46,8 @@ class BasicMessageChannel<T> {
   final MessageCodec<T> codec;
 
   /// The messenger which sends the bytes for this channel, not null.
-  final BinaryMessenger binaryMessenger;
+  BinaryMessenger get binaryMessenger => _binaryMessenger ?? defaultBinaryMessenger; // ignore: deprecated_member_use_from_same_package
+  final BinaryMessenger _binaryMessenger;
 
   /// Sends the specified [message] to the platform plugins on this channel.
   ///
@@ -118,11 +121,12 @@ class MethodChannel {
   /// The [codec] used will be [StandardMethodCodec], unless otherwise
   /// specified.
   ///
-  /// None of [name], [binaryMessenger], or [codec] may be null.
-  const MethodChannel(this.name, [this.codec = const StandardMethodCodec(), this.binaryMessenger = defaultBinaryMessenger ])
-    : assert(name != null),
-      assert(binaryMessenger != null),
-      assert(codec != null);
+  /// The [name] and [codec] arguments cannot be null. The default [ServicesBinding.defaultBinaryMessenger]
+  /// instance is used if [binaryMessenger] is null.
+  const MethodChannel(this.name, [this.codec = const StandardMethodCodec(), BinaryMessenger binaryMessenger ])
+      : assert(name != null),
+        assert(codec != null),
+        _binaryMessenger = binaryMessenger;
 
   /// The logical channel on which communication happens, not null.
   final String name;
@@ -133,7 +137,8 @@ class MethodChannel {
   /// The messenger used by this channel to send platform messages.
   ///
   /// The messenger may not be null.
-  final BinaryMessenger binaryMessenger;
+  BinaryMessenger get binaryMessenger => _binaryMessenger ?? defaultBinaryMessenger; // ignore: deprecated_member_use_from_same_package
+  final BinaryMessenger _binaryMessenger;
 
   /// Invokes a [method] on this channel with the specified [arguments].
   ///
@@ -462,8 +467,12 @@ class EventChannel {
   /// The [codec] used will be [StandardMethodCodec], unless otherwise
   /// specified.
   ///
-  /// Neither [name] nor [codec] may be null.
-  const EventChannel(this.name, [this.codec = const StandardMethodCodec()]);
+  /// Neither [name] nor [codec] may be null. The default [ServicesBinding.defaultBinaryMessenger]
+  /// instance is used if [binaryMessenger] is null.
+  const EventChannel(this.name, [this.codec = const StandardMethodCodec(), BinaryMessenger binaryMessenger])
+      : assert(name != null),
+        assert(codec != null),
+        _binaryMessenger = binaryMessenger;
 
   /// The logical channel on which communication happens, not null.
   final String name;
@@ -471,6 +480,10 @@ class EventChannel {
   /// The message codec used by this channel, not null.
   final MethodCodec codec;
 
+  /// The messenger used by this channel to send platform messages, not null.
+  BinaryMessenger get binaryMessenger => _binaryMessenger ?? defaultBinaryMessenger; // ignore: deprecated_member_use_from_same_package
+  final BinaryMessenger _binaryMessenger;
+
   /// Sets up a broadcast stream for receiving events on this channel.
   ///
   /// Returns a broadcast [Stream] which emits events to listeners as follows:
@@ -488,7 +501,7 @@ class EventChannel {
     final MethodChannel methodChannel = MethodChannel(name, codec);
     StreamController<dynamic> controller;
     controller = StreamController<dynamic>.broadcast(onListen: () async {
-      defaultBinaryMessenger.setMessageHandler(name, (ByteData reply) async {
+      binaryMessenger.setMessageHandler(name, (ByteData reply) async {
         if (reply == null) {
           controller.close();
         } else {
@@ -511,7 +524,7 @@ class EventChannel {
         ));
       }
     }, onCancel: () async {
-      defaultBinaryMessenger.setMessageHandler(name, null);
+      binaryMessenger.setMessageHandler(name, null);
       try {
         await methodChannel.invokeMethod<void>('cancel', arguments);
       } catch (exception, stack) {

packages/flutter/lib/src/services/platform_messages.dart

@@ -7,7 +7,6 @@ import 'dart:typed_data';
 import 'dart:ui' as ui;
 
 import 'binary_messenger.dart';
-import 'binding.dart' show ServicesBinding;
 import 'platform_channel.dart';
 
 /// Sends binary messages to and receives binary messages from platform plugins.
@@ -31,6 +30,9 @@ import 'platform_channel.dart';
 class BinaryMessages {
   BinaryMessages._();
 
+  /// The messenger which sends the platform messages, not null.
+  static final BinaryMessenger _binaryMessenger = defaultBinaryMessenger;
+
   /// Calls the handler registered for the given channel.
   ///
   /// Typically called by [ServicesBinding] to handle platform messages received
@@ -43,7 +45,7 @@ class BinaryMessages {
     ByteData data,
     ui.PlatformMessageResponseCallback callback,
   ) {
-    return defaultBinaryMessenger.handlePlatformMessage(channel, data, callback);
+    return _binaryMessenger.handlePlatformMessage(channel, data, callback);
   }
 
   /// Send a binary message to the platform plugins on the given channel.
@@ -52,7 +54,7 @@ class BinaryMessages {
   /// binary form.
   @Deprecated('Use defaultBinaryMessenger.send instead.')
   static Future<ByteData> send(String channel, ByteData message) {
-    return defaultBinaryMessenger.send(channel, message);
+    return _binaryMessenger.send(channel, message);
   }
 
   /// Set a callback for receiving messages from the platform plugins on the
@@ -65,7 +67,7 @@ class BinaryMessages {
   /// The handler's return value, if non-null, is sent as a response, unencoded.
   @Deprecated('Use defaultBinaryMessenger.setMessageHandler instead.')
   static void setMessageHandler(String channel, Future<ByteData> handler(ByteData message)) {
-    defaultBinaryMessenger.setMessageHandler(channel, handler);
+    _binaryMessenger.setMessageHandler(channel, handler);
   }
 
   /// Set a mock callback for intercepting messages from the `send*` methods on
@@ -81,6 +83,6 @@ class BinaryMessages {
   /// sent to platform plugins.
   @Deprecated('Use defaultBinaryMessenger.setMockMessageHandler instead.')
   static void setMockMessageHandler(String channel, Future<ByteData> handler(ByteData message)) {
-    defaultBinaryMessenger.setMockMessageHandler(channel, handler);
+    _binaryMessenger.setMockMessageHandler(channel, handler);
   }
 }

packages/flutter/lib/src/widgets/binding.dart

@@ -251,6 +251,10 @@ mixin WidgetsBinding on BindingBase, SchedulerBinding, GestureBinding, RendererB
   void initInstances() {
     super.initInstances();
     _instance = this;
+    // Initialization of [_buildOwner] has to be done after
+    // [super.initInstances] is called, as it requires [ServicesBinding] to
+    // properly setup the [defaultBinaryMessenger] instance.
+    _buildOwner = BuildOwner();
     buildOwner.onBuildScheduled = _handleBuildScheduled;
     window.onLocaleChanged = handleLocaleChanged;
     window.onAccessibilityFeaturesChanged = handleAccessibilityFeaturesChanged;
@@ -371,7 +375,10 @@ mixin WidgetsBinding on BindingBase, SchedulerBinding, GestureBinding, RendererB
   /// The [BuildOwner] in charge of executing the build pipeline for the
   /// widget tree rooted at this binding.
   BuildOwner get buildOwner => _buildOwner;
-  final BuildOwner _buildOwner = BuildOwner();
+  // Initialization of [_buildOwner] has to be done within the [initInstances]
+  // method, as it requires [ServicesBinding] to properly setup the
+  // [defaultBinaryMessenger] instance.
+  BuildOwner _buildOwner;
 
   /// The object in charge of the focus tree.
   ///

packages/flutter/test/cupertino/text_field_test.dart

@@ -125,6 +125,7 @@ class PathPointsMatcher extends Matcher {
 
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
   final MockClipboard mockClipboard = MockClipboard();
   SystemChannels.platform.setMockMethodCallHandler(mockClipboard.handleMethodCall);
 

packages/flutter/test/foundation/service_extensions_test.dart

@@ -433,7 +433,7 @@ void main() {
     bool completed;
 
     completed = false;
-    defaultBinaryMessenger.setMockMessageHandler('flutter/assets', (ByteData message) async {
+    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', (ByteData message) async {
       expect(utf8.decode(message.buffer.asUint8List()), 'test');
       completed = true;
       return ByteData(5); // 0x0000000000
@@ -452,7 +452,7 @@ void main() {
     data = await rootBundle.loadStructuredData<bool>('test', (String value) async { expect(value, '\x00\x00\x00\x00\x00'); return false; });
     expect(data, isFalse);
     expect(completed, isTrue);
-    defaultBinaryMessenger.setMockMessageHandler('flutter/assets', null);
+    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', null);
   });
 
   test('Service extensions - exit', () async {

packages/flutter/test/material/search_test.dart

@@ -72,7 +72,7 @@ void main() {
 
     // Simulate system back button
     final ByteData message = const JSONMethodCodec().encodeMethodCall(const MethodCall('popRoute'));
-    await defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
+    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
 
     expect(selectedResults, <void>[null]);

packages/flutter/test/material/text_field_test.dart

@@ -129,6 +129,7 @@ double getOpacity(WidgetTester tester, Finder finder) {
 }
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
   final MockClipboard mockClipboard = MockClipboard();
   SystemChannels.platform.setMockMethodCallHandler(mockClipboard.handleMethodCall);
 
@@ -3391,7 +3392,7 @@ void main() {
   });
 
   void sendFakeKeyEvent(Map<String, dynamic> data) {
-    defaultBinaryMessenger.handlePlatformMessage(
+    ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
       SystemChannels.keyEvent.name,
       SystemChannels.keyEvent.codec.encodeMessage(data),
           (ByteData data) { },

packages/flutter/test/scheduler/ticker_test.dart

@@ -129,7 +129,7 @@ void main() {
     expect(tickCount, equals(0));
 
     final ByteData message = const StringCodec().encodeMessage('AppLifecycleState.paused');
-    await defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) { });
+    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', message, (_) { });
     expect(ticker.isTicking, isFalse);
     expect(ticker.isActive, isTrue);
 
@@ -138,7 +138,7 @@ void main() {
 
   testWidgets('Ticker can be created before application unpauses', (WidgetTester tester) async {
     final ByteData pausedMessage = const StringCodec().encodeMessage('AppLifecycleState.paused');
-    await defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', pausedMessage, (_) { });
+    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', pausedMessage, (_) { });
 
     int tickCount = 0;
     void handleTick(Duration duration) {
@@ -157,7 +157,7 @@ void main() {
     expect(ticker.isTicking, isFalse);
 
     final ByteData resumedMessage = const StringCodec().encodeMessage('AppLifecycleState.resumed');
-    await defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', resumedMessage, (_) { });
+    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/lifecycle', resumedMessage, (_) { });
 
     await tester.pump(const Duration(milliseconds: 10));
 

packages/flutter/test/semantics/semantics_service_test.dart

@@ -6,10 +6,13 @@ import 'dart:ui' show TextDirection;
 
 import 'package:flutter/semantics.dart';
 import 'package:flutter/services.dart' show SystemChannels;
+import 'package:flutter_test/flutter_test.dart' show TestWidgetsFlutterBinding;
 
 import '../flutter_test_alternative.dart';
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
   test('Semantic announcement', () async {
     final List<Map<dynamic, dynamic>> log = <Map<dynamic, dynamic>>[];
 

packages/flutter/test/services/fake_platform_views.dart

@@ -71,7 +71,7 @@ class FakeAndroidPlatformViewsController {
   void invokeViewFocused(int viewId) {
     final MethodCodec codec = SystemChannels.platform_views.codec;
     final ByteData data = codec.encodeMethodCall(MethodCall('viewFocused', viewId));
-    defaultBinaryMessenger.handlePlatformMessage(SystemChannels.platform_views.name, data, (ByteData data) {});
+    ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(SystemChannels.platform_views.name, data, (ByteData data) {});
   }
 
   Future<dynamic> _onMethodCall(MethodCall call) {

packages/flutter/test/services/haptic_feedback_test.dart

@@ -6,6 +6,8 @@ import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
   test('Haptic feedback control test', () async {
     final List<MethodCall> log = <MethodCall>[];
 

packages/flutter/test/services/platform_channel_test.dart

@@ -6,14 +6,18 @@ import 'dart:async';
 import 'dart:typed_data';
 
 import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart' show TestWidgetsFlutterBinding;
+
 import '../flutter_test_alternative.dart';
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
   group('BasicMessageChannel', () {
     const MessageCodec<String> string = StringCodec();
     const BasicMessageChannel<String> channel = BasicMessageChannel<String>('ch', string);
     test('can send string message and get reply', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch',
         (ByteData message) async => string.encodeMessage(string.decodeMessage(message) + ' world'),
       );
@@ -23,7 +27,7 @@ void main() {
     test('can receive string message and send reply', () async {
       channel.setMessageHandler((String message) async => message + ' world');
       String reply;
-      await defaultBinaryMessenger.handlePlatformMessage(
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
         'ch',
         const StringCodec().encodeMessage('hello'),
         (ByteData replyBinary) {
@@ -39,7 +43,7 @@ void main() {
     const MethodCodec jsonMethod = JSONMethodCodec();
     const MethodChannel channel = MethodChannel('ch7', jsonMethod);
     test('can invoke method and get result', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch7',
         (ByteData message) async {
           final Map<dynamic, dynamic> methodCall = jsonMessage.decodeMessage(message);
@@ -54,7 +58,7 @@ void main() {
       expect(result, equals('hello world'));
     });
     test('can invoke list method and get result', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch7',
         (ByteData message) async {
           final Map<dynamic, dynamic> methodCall = jsonMessage.decodeMessage(message);
@@ -70,7 +74,7 @@ void main() {
     });
 
     test('can invoke list method and get null result', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch7',
         (ByteData message) async {
           final Map<dynamic, dynamic> methodCall = jsonMessage.decodeMessage(message);
@@ -86,7 +90,7 @@ void main() {
 
 
     test('can invoke map method and get result', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch7',
         (ByteData message) async {
           final Map<dynamic, dynamic> methodCall = jsonMessage.decodeMessage(message);
@@ -102,7 +106,7 @@ void main() {
     });
 
     test('can invoke map method and get null result', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch7',
         (ByteData message) async {
           final Map<dynamic, dynamic> methodCall = jsonMessage.decodeMessage(message);
@@ -117,7 +121,7 @@ void main() {
     });
 
     test('can invoke method and get error', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch7',
         (ByteData message) async {
           return jsonMessage.encodeMessage(<dynamic>[
@@ -139,7 +143,7 @@ void main() {
       }
     });
     test('can invoke unimplemented method', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch7',
         (ByteData message) async => null,
       );
@@ -157,7 +161,7 @@ void main() {
       channel.setMethodCallHandler(null);
       final ByteData call = jsonMethod.encodeMethodCall(const MethodCall('sayHello', 'hello'));
       ByteData envelope;
-      await defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
         envelope = result;
       });
       expect(envelope, isNull);
@@ -168,7 +172,7 @@ void main() {
       });
       final ByteData call = jsonMethod.encodeMethodCall(const MethodCall('sayHello', 'hello'));
       ByteData envelope;
-      await defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
         envelope = result;
       });
       expect(envelope, isNull);
@@ -177,7 +181,7 @@ void main() {
       channel.setMethodCallHandler((MethodCall call) async => '${call.arguments}, world');
       final ByteData call = jsonMethod.encodeMethodCall(const MethodCall('sayHello', 'hello'));
       ByteData envelope;
-      await defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
         envelope = result;
       });
       expect(jsonMethod.decodeEnvelope(envelope), equals('hello, world'));
@@ -188,7 +192,7 @@ void main() {
       });
       final ByteData call = jsonMethod.encodeMethodCall(const MethodCall('sayHello', 'hello'));
       ByteData envelope;
-      await defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
         envelope = result;
       });
       try {
@@ -207,7 +211,7 @@ void main() {
       });
       final ByteData call = jsonMethod.encodeMethodCall(const MethodCall('sayHello', 'hello'));
       ByteData envelope;
-      await defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
+      await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('ch7', call, (ByteData result) {
         envelope = result;
       });
       try {
@@ -226,7 +230,7 @@ void main() {
     const MethodCodec jsonMethod = JSONMethodCodec();
     const EventChannel channel = EventChannel('ch', jsonMethod);
     void emitEvent(dynamic event) {
-      defaultBinaryMessenger.handlePlatformMessage(
+      ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
         'ch',
         event,
             (ByteData reply) { },
@@ -234,7 +238,7 @@ void main() {
     }
     test('can receive event stream', () async {
       bool canceled = false;
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch',
         (ByteData message) async {
           final Map<dynamic, dynamic> methodCall = jsonMessage.decodeMessage(message);
@@ -258,7 +262,7 @@ void main() {
       expect(canceled, isTrue);
     });
     test('can receive error event', () async {
-      defaultBinaryMessenger.setMockMessageHandler(
+      ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler(
         'ch',
         (ByteData message) async {
           final Map<dynamic, dynamic> methodCall = jsonMessage.decodeMessage(message);

packages/flutter/test/services/platform_messages_test.dart

@@ -16,18 +16,18 @@ void main() {
 
     final List<ByteData> log = <ByteData>[];
 
-    defaultBinaryMessenger.setMockMessageHandler('test1', (ByteData message) async {
+    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('test1', (ByteData message) async {
       log.add(message);
       return null;
     });
 
     final ByteData message = ByteData(2)..setUint16(0, 0xABCD);
-    await defaultBinaryMessenger.send('test1', message);
+    await ServicesBinding.instance.defaultBinaryMessenger.send('test1', message);
     expect(log, equals(<ByteData>[message]));
     log.clear();
 
-    defaultBinaryMessenger.setMockMessageHandler('test1', null);
-    await defaultBinaryMessenger.send('test1', message);
+    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('test1', null);
+    await ServicesBinding.instance.defaultBinaryMessenger.send('test1', message);
     expect(log, isEmpty);
   });
 }

packages/flutter/test/services/platform_views_test.dart

@@ -4,11 +4,13 @@
 
 import 'package:flutter/painting.dart';
 import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart' show TestWidgetsFlutterBinding;
 import '../flutter_test_alternative.dart';
 
 import 'fake_platform_views.dart';
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
 
   group('Android', () {
     FakeAndroidPlatformViewsController viewsController;

packages/flutter/test/services/system_chrome_test.dart

@@ -61,7 +61,7 @@ void main() {
   test('setApplicationSwitcherDescription missing plugin', () async {
     final List<ByteData> log = <ByteData>[];
 
-    defaultBinaryMessenger.setMockMessageHandler('flutter/platform', (ByteData message) {
+    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('flutter/platform', (ByteData message) {
       log.add(message);
       return null;
     });

packages/flutter/test/services/system_navigator_test.dart

@@ -6,6 +6,8 @@ import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
   test('System navigator control test', () async {
     final List<MethodCall> log = <MethodCall>[];
 

packages/flutter/test/services/system_sound_test.dart

@@ -6,6 +6,8 @@ import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
   test('System sound control test', () async {
     final List<MethodCall> log = <MethodCall>[];
 

packages/flutter/test/services/text_input_test.dart

@@ -3,9 +3,12 @@
 // found in the LICENSE file.
 
 import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart' show TestWidgetsFlutterBinding;
 import '../flutter_test_alternative.dart';
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
   group('TextInputConfiguration', () {
     test('sets expected defaults', () {
       const TextInputConfiguration configuration = TextInputConfiguration();
@@ -103,7 +106,7 @@ void main() {
             'method': 'TextInputClient.onConnectionClosed',
           }
       );
-      defaultBinaryMessenger.handlePlatformMessage(
+      ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
         'flutter/textinput',
         messageBytes,
         (ByteData _) {},

packages/flutter/test/widgets/binding_test.dart

@@ -46,12 +46,13 @@ void main() {
     WidgetsBinding.instance.addObserver(observer);
     final ByteData message = const JSONMessageCodec().encodeMessage(
       <String, dynamic>{'type': 'memoryPressure'});
-    await defaultBinaryMessenger.handlePlatformMessage('flutter/system', message, (_) { });
+    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/system', message, (_) { });
     expect(observer.sawMemoryPressure, true);
     WidgetsBinding.instance.removeObserver(observer);
   });
 
   testWidgets('handleLifecycleStateChanged callback', (WidgetTester tester) async {
+    final BinaryMessenger defaultBinaryMessenger = ServicesBinding.instance.defaultBinaryMessenger;
     final AppLifecycleStateObserver observer = AppLifecycleStateObserver();
     WidgetsBinding.instance.addObserver(observer);
 
@@ -79,13 +80,14 @@ void main() {
     const String testRouteName = 'testRouteName';
     final ByteData message = const JSONMethodCodec().encodeMethodCall(
       const MethodCall('pushRoute', testRouteName));
-    await defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
+    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     expect(observer.pushedRoute, testRouteName);
 
     WidgetsBinding.instance.removeObserver(observer);
   });
 
   testWidgets('Application lifecycle affects frame scheduling', (WidgetTester tester) async {
+    final BinaryMessenger defaultBinaryMessenger = ServicesBinding.instance.defaultBinaryMessenger;
     ByteData message;
     expect(tester.binding.hasScheduledFrame, isFalse);
 

packages/flutter/test/widgets/focus_manager_test.dart

@@ -10,7 +10,7 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void sendFakeKeyEvent(Map<String, dynamic> data) {
-  defaultBinaryMessenger.handlePlatformMessage(
+  ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
     SystemChannels.keyEvent.name,
     SystemChannels.keyEvent.codec.encodeMessage(data),
     (ByteData data) {},

packages/flutter/test/widgets/raw_keyboard_listener_test.dart

@@ -9,7 +9,7 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void sendFakeKeyEvent(Map<String, dynamic> data) {
-  defaultBinaryMessenger.handlePlatformMessage(
+  ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
     SystemChannels.keyEvent.name,
     SystemChannels.keyEvent.codec.encodeMessage(data),
     (ByteData data) {},

packages/flutter/test/widgets/selectable_text_test.dart

@@ -122,6 +122,7 @@ double getOpacity(WidgetTester tester, Finder finder) {
 }
 
 void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
   final MockClipboard mockClipboard = MockClipboard();
   SystemChannels.platform.setMockMethodCallHandler(mockClipboard.handleMethodCall);
 
@@ -1247,7 +1248,7 @@ void main() {
   });
 
   void sendFakeKeyEvent(Map<String, dynamic> data) {
-    defaultBinaryMessenger.handlePlatformMessage(
+    ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
       SystemChannels.keyEvent.name,
       SystemChannels.keyEvent.codec.encodeMessage(data),
           (ByteData data) { },

packages/flutter/test/widgets/shortcuts_test.dart

@@ -11,7 +11,7 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void sendFakeKeyEvent(Map<String, dynamic> data) {
-  defaultBinaryMessenger.handlePlatformMessage(
+  ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
     SystemChannels.keyEvent.name,
     SystemChannels.keyEvent.codec.encodeMessage(data),
     (ByteData data) {},

packages/flutter_test/lib/src/binding.dart

@@ -207,10 +207,10 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
 
   @override
   void initInstances() {
+    super.initInstances();
     timeDilation = 1.0; // just in case the developer has artificially changed it for development
     HttpOverrides.global = _MockHttpOverrides();
     _testTextInput = TestTextInput(onCleared: _resetFocusedEditable)..register();
-    super.initInstances();
   }
 
   @override
@@ -812,7 +812,7 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
     /// platform messages.
     SystemChannels.navigation.setMockMethodCallHandler((MethodCall methodCall) async {});
 
-    defaultBinaryMessenger.setMockMessageHandler('flutter/assets', (ByteData message) {
+    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', (ByteData message) {
       String key = utf8.decode(message.buffer.asUint8List());
       File asset = File(path.join(assetFolderPath, key));
 

packages/flutter_test/lib/src/test_text_input.dart

@@ -36,6 +36,9 @@ class TestTextInput {
   /// first be requested, e.g. using [WidgetTester.showKeyboard].
   final VoidCallback onCleared;
 
+  /// The messenger which sends the bytes for this channel, not null.
+  BinaryMessenger get _binaryMessenger => ServicesBinding.instance.defaultBinaryMessenger;
+
   /// Installs this object as a mock handler for [SystemChannels.textInput].
   void register() {
     SystemChannels.textInput.setMockMethodCallHandler(_handleTextInputCall);
@@ -108,7 +111,7 @@ class TestTextInput {
     // test this code does not run in a package:test test zone.
     if (_client == 0)
       throw TestFailure('Tried to use TestTextInput with no keyboard attached. You must use WidgetTester.showKeyboard() first.');
-    defaultBinaryMessenger.handlePlatformMessage(
+    _binaryMessenger.handlePlatformMessage(
       SystemChannels.textInput.name,
       SystemChannels.textInput.codec.encodeMethodCall(
         MethodCall(
@@ -140,7 +143,7 @@ class TestTextInput {
 
       final Completer<void> completer = Completer<void>();
 
-      defaultBinaryMessenger.handlePlatformMessage(
+      _binaryMessenger.handlePlatformMessage(
         SystemChannels.textInput.name,
         SystemChannels.textInput.codec.encodeMethodCall(
           MethodCall(