[platform_channels] Migrate to sound null safety (#803)

platform_channels/android/app/src/main/kotlin/dev/flutter/platform_channels/AccelerometerStreamHandler.kt

@@ -32,6 +32,8 @@ class AccelerometerStreamHandler(sManager: SensorManager, s: Sensor) : EventChan
         if (sensorEvent != null) {
             val axisValues = listOf(sensorEvent.values[0], sensorEvent.values[1], sensorEvent.values[2])
             eventSink.success(axisValues)
+        } else {
+            eventSink.error("DATA_UNAVAILABLE", "Cannot get accelerometer data", null)
         }
     }
 }

platform_channels/ios/Runner.xcodeproj/project.xcworkspace/contents.xcworkspacedata

@@ -2,6 +2,6 @@
 <Workspace
    version = "1.0">
    <FileRef
-      location = "group:Runner.xcodeproj">
+      location = "self:">
    </FileRef>
 </Workspace>

platform_channels/lib/main.dart

@@ -39,9 +39,7 @@ class DemoInfo {
   final String demoTitle;
   final String demoRoute;
 
-  DemoInfo(this.demoTitle, this.demoRoute)
+  DemoInfo(this.demoTitle, this.demoRoute);
-      : assert(demoTitle != null),
-        assert(demoRoute != null);
 }
 
 List<DemoInfo> demoList = [

platform_channels/lib/src/add_pet_details.dart

@@ -64,7 +64,7 @@ class _AddPetDetailsState extends State<AddPetDetails> {
               groupValue: petType,
               onChanged: (value) {
                 setState(() {
-                  petType = value;
+                  petType = value!;
                 });
               },
             ),
@@ -74,7 +74,7 @@ class _AddPetDetailsState extends State<AddPetDetails> {
               groupValue: petType,
               onChanged: (value) {
                 setState(() {
-                  petType = value;
+                  petType = value!;
                 });
               },
             ),

platform_channels/lib/src/counter_method_channel.dart

@@ -14,16 +14,16 @@ class Counter {
   static MethodChannel methodChannel = const MethodChannel('methodChannelDemo');
 
   /// This method is responsible to increment and return the value of count.
-  static Future<int> increment({int counterValue}) async {
+  static Future<int> increment({required int counterValue}) async {
     final result = await methodChannel
         .invokeMethod<int>('increment', {'count': counterValue});
-    return result;
+    return result!;
   }
 
   /// This method is responsible to decrement and return the value of count.
-  static Future<int> decrement({int counterValue}) async {
+  static Future<int> decrement({required int counterValue}) async {
     final result = await methodChannel
         .invokeMethod<int>('decrement', {'count': counterValue});
-    return result;
+    return result!;
   }
 }

platform_channels/lib/src/event_channel_demo.dart

@@ -26,21 +26,21 @@ class EventChannelDemo extends StatelessWidget {
           stream: Accelerometer.readings,
           builder: (context, snapshot) {
             if (snapshot.hasError) {
-              return Text((snapshot.error as PlatformException).message);
+              return Text((snapshot.error as PlatformException).message!);
             } else if (snapshot.hasData) {
               return Column(
                 mainAxisAlignment: MainAxisAlignment.center,
                 children: [
                   Text(
-                    'x axis: ' + snapshot.data.x.toStringAsFixed(3),
+                    'x axis: ' + snapshot.data!.x.toStringAsFixed(3),
                     style: textStyle,
                   ),
                   Text(
-                    'y axis: ' + snapshot.data.y.toStringAsFixed(3),
+                    'y axis: ' + snapshot.data!.y.toStringAsFixed(3),
                     style: textStyle,
                   ),
                   Text(
-                    'z axis: ' + snapshot.data.z.toStringAsFixed(3),
+                    'z axis: ' + snapshot.data!.z.toStringAsFixed(3),
                     style: textStyle,
                   )
                 ],

platform_channels/lib/src/image_basic_message_channel.dart

@@ -15,7 +15,7 @@ class PlatformImageFetcher {
 
   /// Method responsible for providing the platform image.
   static Future<Uint8List> getImage() async {
-    final reply = await _basicMessageChannel.send('getImage') as Uint8List;
+    final reply = await _basicMessageChannel.send('getImage') as Uint8List?;
     if (reply == null) {
       throw PlatformException(
         code: 'Error',

platform_channels/lib/src/method_channel_demo.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:platform_channels/src/counter_method_channel.dart';
 
 /// The widget demonstrates how to use [MethodChannel] to invoke platform methods.
@@ -45,7 +46,7 @@ class _MethodChannelDemoState extends State<MethodChannelDemo> {
                   } catch (error) {
                     showErrorMessage(
                       context,
-                      error.message as String,
+                      (error as PlatformException).message!,
                     );
                   }
                 },
@@ -63,7 +64,7 @@ class _MethodChannelDemoState extends State<MethodChannelDemo> {
                   } catch (error) {
                     showErrorMessage(
                       context,
-                      error.message as String,
+                      (error as PlatformException).message!,
                     );
                   }
                 },

platform_channels/lib/src/pet_list_message_channel.dart

@@ -44,7 +44,7 @@ class PetListMessageChannel {
 /// A model class that provides [petList] which is received from platform.
 class PetListModel {
   PetListModel({
-    this.petList,
+    required this.petList,
   });
 
   final List<PetDetails> petList;
@@ -65,8 +65,8 @@ class PetListModel {
 /// A simple model that provides pet details like [petType] and [breed] of pet.
 class PetDetails {
   PetDetails({
-    this.petType,
+    required this.petType,
-    this.breed,
+    required this.breed,
   });
 
   final String petType;

platform_channels/lib/src/pet_list_screen.dart

@@ -14,7 +14,7 @@ class PetListScreen extends StatefulWidget {
 }
 
 class _PetListScreenState extends State<PetListScreen> {
-  PetListModel petListModel;
+  PetListModel petListModel = PetListModel(petList: []);
   final scaffoldKey = GlobalKey<ScaffoldState>();
 
   @override
@@ -22,7 +22,7 @@ class _PetListScreenState extends State<PetListScreen> {
     super.initState();
     // Receives a string of json object from the platform and converts it
     // to PetModel.
-    const BasicMessageChannel('stringCodecDemo', StringCodec())
+    const BasicMessageChannel<String?>('stringCodecDemo', StringCodec())
         .setMessageHandler((message) async {
       if (message == null) {
         showSnackBar('An error occurred while adding pet details.', context);
@@ -31,7 +31,7 @@ class _PetListScreenState extends State<PetListScreen> {
           petListModel = PetListModel.fromJson(message);
         });
       }
-      return;
+      return null;
     });
   }
 
@@ -48,7 +48,7 @@ class _PetListScreenState extends State<PetListScreen> {
           Navigator.pushNamed(context, '/addPetDetails');
         },
       ),
-      body: petListModel?.petList?.isEmpty ?? true
+      body: petListModel.petList.isEmpty
           ? const Center(child: Text('Enter Pet Details'))
           : BuildPetList(petListModel.petList),
     );
@@ -79,7 +79,7 @@ class BuildPetList extends StatelessWidget {
                 await PetListMessageChannel.removePet(index);
                 showSnackBar('Removed successfully!', context);
               } catch (error) {
-                showSnackBar(error.message.toString(), context);
+                showSnackBar((error as PlatformException).message!, context);
               }
             },
           ),

platform_channels/lib/src/platform_image_demo.dart

@@ -18,7 +18,7 @@ class PlatformImageDemo extends StatefulWidget {
 }
 
 class _PlatformImageDemoState extends State<PlatformImageDemo> {
-  Future<Uint8List> imageData;
+  Future<Uint8List>? imageData;
 
   @override
   Widget build(BuildContext context) {
@@ -41,12 +41,14 @@ class _PlatformImageDemoState extends State<PlatformImageDemo> {
                       return const Placeholder();
                     } else if (snapshot.hasError) {
                       return Center(
-                        child: Text(snapshot.error.toString()),
+                        child: Text(
+                          (snapshot.error as PlatformException).message!,
+                        ),
                       );
                     } else if (snapshot.connectionState ==
                         ConnectionState.done) {
                       return Image.memory(
-                        snapshot.data,
+                        snapshot.data!,
                         fit: BoxFit.fill,
                       );
                     }

platform_channels/pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.6.1"
+    version: "2.5.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -113,7 +113,7 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.1"
+    version: "1.8.0"
   stack_trace:
     dependency: transitive
     description:
@@ -148,7 +148,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.3.0"
+    version: "0.2.19"
   typed_data:
     dependency: transitive
     description:

platform_channels/pubspec.yaml

@@ -4,13 +4,13 @@ description: A new Flutter project.
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter:
     sdk: flutter
 
-  cupertino_icons: ^1.0.0
+  cupertino_icons: ^1.0.3
 
 dev_dependencies:
   flutter_test:

platform_channels/test/src/event_channel_demo_test.dart

@@ -19,8 +19,8 @@ void main() {
       // calls the BinaryMessenger.setMessageHandler registered for the EventChannel
       // and add the incoming message to the StreamController used by the EventChannel
       // after decoding the message with codec used by the EventChannel.
-      void emitValues(ByteData event) {
+      void emitValues(ByteData? event) {
-        ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+        ServicesBinding.instance?.defaultBinaryMessenger.handlePlatformMessage(
           'eventChannelDemo',
           event,
           (reply) {},
@@ -29,7 +29,7 @@ void main() {
 
       // Register a mock for EventChannel. EventChannel under the hood uses
       // MethodChannel to listen and cancel the created stream.
-      ServicesBinding.instance.defaultBinaryMessenger
+      ServicesBinding.instance?.defaultBinaryMessenger
           .setMockMessageHandler('eventChannelDemo', (message) async {
         // Decode the message into MethodCallHandler.
         final methodCall = standardMethod.decodeMethodCall(message);

platform_channels/test/src/pet_list_screen_test.dart

@@ -13,7 +13,7 @@ import 'package:platform_channels/src/pet_list_screen.dart';
 void main() {
   group('PetListScreen tests', () {
     const basicMessageChannel =
-        BasicMessageChannel('stringCodecDemo', StringCodec());
+        BasicMessageChannel<String?>('stringCodecDemo', StringCodec());
 
     var petList = [
       {
@@ -22,21 +22,21 @@ void main() {
       }
     ];
 
-    PetListModel petListModel;
+    PetListModel? petListModel;
 
     setUpAll(() {
       // Mock for the pet list received from the platform.
       basicMessageChannel.setMockMessageHandler((message) async {
-        petListModel = PetListModel.fromJson(message);
+        petListModel = PetListModel.fromJson(message!);
-        return;
+        return null;
       });
 
       // Mock for the index received from the Dart to delete the pet details,
       // and send the updated pet list back to Dart.
-      const BasicMessageChannel('binaryCodecDemo', BinaryCodec())
+      const BasicMessageChannel<ByteData?>('binaryCodecDemo', BinaryCodec())
           .setMockMessageHandler((message) async {
         // Convert the ByteData to String.
-        final index = utf8.decoder.convert(message.buffer
+        final index = utf8.decoder.convert(message!.buffer
             .asUint8List(message.offsetInBytes, message.lengthInBytes));
 
         // Remove the pet details at the given index.
@@ -45,7 +45,8 @@ void main() {
         // Send the updated petList back.
         final map = {'petList': petList};
         await basicMessageChannel.send(json.encode(map));
-        return;
+
+        return null;
       });
     });
 
@@ -60,7 +61,7 @@ void main() {
       basicMessageChannel.send(json.encode(map));
 
       // Get the details of first pet.
-      final petDetails = petListModel.petList.first;
+      final petDetails = petListModel!.petList.first;
       expect(petDetails.petType, 'Dog');
       expect(petDetails.breed, 'Pug');
     });
@@ -68,7 +69,7 @@ void main() {
     testWidgets('BuildPetList test', (tester) async {
       await tester.pumpWidget(MaterialApp(
         home: Scaffold(
-          body: BuildPetList(petListModel.petList),
+          body: BuildPetList(petListModel!.petList),
         ),
       ));
 
@@ -77,7 +78,7 @@ void main() {
 
       // Delete the pet details.
       await tester.tap(find.byIcon(Icons.delete).first);
-      expect(petListModel.petList, isEmpty);
+      expect(petListModel!.petList, isEmpty);
     });
   });
 }