refactor: applying lint suggestions

No breaking changes.

analysis_options.yaml

@@ -1,6 +1,239 @@
+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
 include: package:flutter_lints/flutter.yaml
 
-# Additional information about this file can be found at
-# https://dart.dev/guides/language/analysis-options
 analyzer:
-  exclude: [lib/generated_bindings.dart]
+  language:
+    strict-casts: false
+    strict-raw-types: true
+  errors:
+    # treat missing required parameters as a warning (not a hint)
+    missing_required_param: warning
+    # treat missing returns as a warning (not a hint)
+    missing_return: warning
+    # not allowing having TODO comments in the code
+    # todo: warning
+    # allow self-reference to deprecated members (we do this because otherwise we have
+    # to annotate every member in every test, assert, etc, when we deprecate something)
+    deprecated_member_use_from_same_package: ignore
+    # Turned off until null-safe rollout is complete.
+    unnecessary_null_comparison: warning
+  exclude:
+    - "bin/cache/**"
+      # Ignore protoc generated files
+    - "dev/conductor/lib/proto/*"
+    - "lib/generated_bindings.dart"
+    
+linter:
+  rules:
+    # This list is derived from the list of all available lints located at
+    # https://github.com/dart-lang/linter/blob/master/example/all.yaml
+    - always_declare_return_types
+    - always_put_control_body_on_new_line
+    # - always_put_required_named_parameters_first # we prefer having parameters in the same order as fields https://github.com/flutter/flutter/issues/10219
+    - always_require_non_null_named_parameters
+    - always_specify_types
+    # - always_use_package_imports # we do this commonly
+    - annotate_overrides
+    # - avoid_annotating_with_dynamic # conflicts with always_specify_types
+    - avoid_bool_literals_in_conditional_expressions
+    # - avoid_catches_without_on_clauses # blocked on https://github.com/dart-lang/linter/issues/3023
+    # - avoid_catching_errors # blocked on https://github.com/dart-lang/linter/issues/3023
+    - avoid_classes_with_only_static_members
+    - avoid_double_and_int_checks
+    - avoid_dynamic_calls
+    - avoid_empty_else
+    - avoid_equals_and_hash_code_on_mutable_classes
+    - avoid_escaping_inner_quotes
+    - avoid_field_initializers_in_const_classes
+    # - avoid_final_parameters # incompatible with prefer_final_parameters
+    - avoid_function_literals_in_foreach_calls
+    - avoid_implementing_value_types
+    - avoid_init_to_null
+    - avoid_js_rounded_ints
+    # - avoid_multiple_declarations_per_line # seems to be a stylistic choice we don't subscribe to
+    - avoid_null_checks_in_equality_operators
+    # - avoid_positional_boolean_parameters # would have been nice to enable this but by now there's too many places that break it
+    - avoid_print
+    # - avoid_private_typedef_functions # we prefer having typedef (discussion in https://github.com/flutter/flutter/pull/16356)
+    - avoid_redundant_argument_values
+    - avoid_relative_lib_imports
+    - avoid_renaming_method_parameters
+    - avoid_return_types_on_setters
+    # - avoid_returning_null # still violated by some pre-nnbd code that we haven't yet migrated
+    - avoid_returning_null_for_future
+    - avoid_returning_null_for_void
+    # - avoid_returning_this # there are enough valid reasons to return `this` that this lint ends up with too many false positives
+    - avoid_setters_without_getters
+    - avoid_shadowing_type_parameters
+    - avoid_single_cascade_in_expression_statements
+    - avoid_slow_async_io
+    - avoid_type_to_string
+    - avoid_types_as_parameter_names
+    # - avoid_types_on_closure_parameters # conflicts with always_specify_types
+    - avoid_unnecessary_containers
+    - avoid_unused_constructor_parameters
+    - avoid_void_async
+    # - avoid_web_libraries_in_flutter # we use web libraries in web-specific code, and our tests prevent us from using them elsewhere
+    - await_only_futures
+    - camel_case_extensions
+    - camel_case_types
+    - cancel_subscriptions
+    # - cascade_invocations # doesn't match the typical style of this repo
+    - cast_nullable_to_non_nullable
+    # - close_sinks # not reliable enough
+    # - comment_references # blocked on https://github.com/dart-lang/linter/issues/1142
+    # - conditional_uri_does_not_exist # not yet tested
+    # - constant_identifier_names # needs an opt-out https://github.com/dart-lang/linter/issues/204
+    - control_flow_in_finally
+    # - curly_braces_in_flow_control_structures # not required by flutter style
+    - depend_on_referenced_packages
+    - deprecated_consistency
+    # - diagnostic_describe_all_properties # enabled only at the framework level (packages/flutter/lib)
+    - directives_ordering
+    # - do_not_use_environment # there are appropriate times to use the environment, especially in our tests and build logic
+    - empty_catches
+    - empty_constructor_bodies
+    - empty_statements
+    - eol_at_end_of_file
+    - exhaustive_cases
+    - file_names
+    - hash_and_equals
+    - implementation_imports
+    # - invariant_booleans # too many false positives: https://github.com/dart-lang/linter/issues/811
+    - iterable_contains_unrelated_type
+    # - join_return_with_assignment # not required by flutter style
+    - leading_newlines_in_multiline_strings
+    - library_names
+    - library_prefixes
+    - library_private_types_in_public_api
+    # - lines_longer_than_80_chars # not required by flutter style
+    - list_remove_unrelated_type
+    # - literal_only_boolean_expressions # too many false positives: https://github.com/dart-lang/linter/issues/453
+    - missing_whitespace_between_adjacent_strings
+    - no_adjacent_strings_in_list
+    - no_default_cases
+    - no_duplicate_case_values
+    - no_leading_underscores_for_library_prefixes
+    - no_leading_underscores_for_local_identifiers
+    - no_logic_in_create_state
+    # - no_runtimeType_toString # ok in tests; we enable this only in packages/
+    - non_constant_identifier_names
+    - noop_primitive_operations
+    - null_check_on_nullable_type_parameter
+    - null_closures
+    # - omit_local_variable_types # opposite of always_specify_types
+    # - one_member_abstracts # too many false positives
+    - only_throw_errors # this does get disabled in a few places where we have legacy code that uses strings et al
+    - overridden_fields
+    - package_api_docs
+    - package_names
+    - package_prefixed_library_names
+    # - parameter_assignments # we do this commonly
+    - prefer_adjacent_string_concatenation
+    - prefer_asserts_in_initializer_lists
+    # - prefer_asserts_with_message # not required by flutter style
+    - prefer_collection_literals
+    - prefer_conditional_assignment
+    - prefer_const_constructors
+    - prefer_const_constructors_in_immutables
+    - prefer_const_declarations
+    - prefer_const_literals_to_create_immutables
+    # - prefer_constructors_over_static_methods # far too many false positives
+    - prefer_contains
+    # - prefer_double_quotes # opposite of prefer_single_quotes
+    - prefer_equal_for_default_values
+    # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
+    - prefer_final_fields
+    - prefer_final_in_for_each
+    - prefer_final_locals
+    # - prefer_final_parameters # we should enable this one day when it can be auto-fixed (https://github.com/dart-lang/linter/issues/3104), see also parameter_assignments
+    - prefer_for_elements_to_map_fromIterable
+    - prefer_foreach
+    - prefer_function_declarations_over_variables
+    - prefer_generic_function_type_aliases
+    - prefer_if_elements_to_conditional_expressions
+    - prefer_if_null_operators
+    - prefer_initializing_formals
+    - prefer_inlined_adds
+    # - prefer_int_literals # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#use-double-literals-for-double-constants
+    - prefer_interpolation_to_compose_strings
+    - prefer_is_empty
+    - prefer_is_not_empty
+    - prefer_is_not_operator
+    - prefer_iterable_whereType
+    # - prefer_mixin # Has false positives, see https://github.com/dart-lang/linter/issues/3018
+    # - prefer_null_aware_method_calls # "call()" is confusing to people new to the language since it's not documented anywhere
+    - prefer_null_aware_operators
+    - prefer_relative_imports
+    - prefer_single_quotes
+    - prefer_spread_collections
+    - prefer_typing_uninitialized_variables
+    - prefer_void_to_null
+    - provide_deprecation_message
+    # - public_member_api_docs # enabled on a case-by-case basis; see e.g. packages/analysis_options.yaml
+    - recursive_getters
+    # - require_trailing_commas # blocked on https://github.com/dart-lang/sdk/issues/47441
+    - secure_pubspec_urls
+    - sized_box_for_whitespace
+    # - sized_box_shrink_expand # not yet tested
+    - slash_for_doc_comments
+    - sort_child_properties_last
+    - sort_constructors_first
+    # - sort_pub_dependencies # prevents separating pinned transitive dependencies
+    - sort_unnamed_constructors_first
+    - test_types_in_equals
+    - throw_in_finally
+    - tighten_type_of_initializing_formals
+    # - type_annotate_public_apis # subset of always_specify_types
+    - type_init_formals
+    # - unawaited_futures # too many false positives, especially with the way AnimationController works
+    - unnecessary_await_in_return
+    - unnecessary_brace_in_string_interps
+    - unnecessary_const
+    - unnecessary_constructor_name
+    # - unnecessary_final # conflicts with prefer_final_locals
+    - unnecessary_getters_setters
+    # - unnecessary_lambdas # has false positives: https://github.com/dart-lang/linter/issues/498
+    - unnecessary_late
+    - unnecessary_new
+    - unnecessary_null_aware_assignments
+    - unnecessary_null_checks
+    - unnecessary_null_in_if_null_operators
+    - unnecessary_nullable_for_final_variable_declarations
+    - unnecessary_overrides
+    - unnecessary_parenthesis
+    # - unnecessary_raw_strings # what's "necessary" is a matter of opinion; consistency across strings can help readability more than this lint
+    - unnecessary_statements
+    - unnecessary_string_escapes
+    - unnecessary_string_interpolations
+    - unnecessary_this
+    - unrelated_type_equality_checks
+    - unsafe_html
+    - use_build_context_synchronously
+    # - use_colored_box # not yet tested
+    # - use_decorated_box # not yet tested
+    # - use_enums # not yet tested
+    - use_full_hex_values_for_flutter_colors
+    - use_function_type_syntax_for_parameters
+    - use_if_null_to_convert_nulls_to_bools
+    - use_is_even_rather_than_modulo
+    - use_key_in_widget_constructors
+    - use_late_for_private_fields_and_variables
+    - use_named_constants
+    - use_raw_strings
+    - use_rethrow_when_possible
+    - use_setters_to_change_properties
+    # - use_string_buffers # has false positives: https://github.com/dart-lang/sdk/issues/34182
+    - use_super_parameters
+    - use_test_throws_matchers
+    # - use_to_and_as_if_applicable # has false positives, so we prefer to catch this by code-review
+    - valid_regexps
+    - void_checks

example/pubspec.lock

@@ -14,7 +14,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.8.2"
+    version: "2.9.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -141,7 +141,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.3.1"
+    version: "0.3.2"
   font_awesome_flutter:
     dependency: "direct main"
     description:

lib/flutter_zxing.dart

@@ -13,11 +13,13 @@ import 'generated_bindings.dart';
 import 'isolate_utils.dart';
 
 export 'generated_bindings.dart';
-export 'reader_widget.dart';
-export 'writer_widget.dart';
 export 'image_converter.dart';
+export 'reader_widget.dart';
 export 'scanner_overlay.dart';
+export 'writer_widget.dart';
 
+// TODO: fix below warning from lint
+// ignore: avoid_classes_with_only_static_members
 /// The main class for reading barcodes from images or camera.
 class FlutterZxing {
   static const MethodChannel _channel = MethodChannel('flutter_zxing');
@@ -27,7 +29,7 @@ class FlutterZxing {
     return version;
   }
 
-  static final bindings = GeneratedBindings(dylib);
+  static final GeneratedBindings bindings = GeneratedBindings(dylib);
 
   static IsolateUtils? isolateUtils;
 
@@ -39,7 +41,7 @@ class FlutterZxing {
   static String version() => bindings.version().cast<Utf8>().toDartString();
 
   /// Starts reading barcode from the camera
-  static Future startCameraProcessing() async {
+  static Future<void> startCameraProcessing() async {
     // Spawn a new isolate
     isolateUtils = IsolateUtils();
     await isolateUtils?.startReadingBarcode();
@@ -66,7 +68,7 @@ class FlutterZxing {
     int cropHeight = 0,
   }) async {
     final Uint8List imageBytes = await path.readAsBytes();
-    imglib.Image? image = imglib.decodeImage(imageBytes);
+    final imglib.Image? image = imglib.decodeImage(imageBytes);
     if (image == null) {
       return null;
     }
@@ -91,7 +93,7 @@ class FlutterZxing {
         (await NetworkAssetBundle(Uri.parse(url)).load(url))
             .buffer
             .asUint8List();
-    imglib.Image? image = imglib.decodeImage(imageBytes);
+    final imglib.Image? image = imglib.decodeImage(imageBytes);
     if (image == null) {
       return null;
     }
@@ -113,9 +115,9 @@ class FlutterZxing {
 
   static List<CodeResult> readBarcodes(Uint8List bytes, int format, int width,
       int height, int cropWidth, int cropHeight) {
-    final result = bindings.readBarcodes(
+    final CodeResults result = bindings.readBarcodes(
         bytes.allocatePointer(), format, width, height, cropWidth, cropHeight);
-    List<CodeResult> results = [];
+    final List<CodeResult> results = <CodeResult>[];
     for (int i = 0; i < result.count; i++) {
       results.add(result.results.elementAt(i).ref);
     }
@@ -124,24 +126,31 @@ class FlutterZxing {
 
   static EncodeResult encodeBarcode(String contents, int width, int height,
       int format, int margin, int eccLevel) {
-    var result = bindings.encodeBarcode(contents.toNativeUtf8().cast<Char>(),
-        width, height, format, margin, eccLevel);
+    final EncodeResult result = bindings.encodeBarcode(
+        contents.toNativeUtf8().cast<Char>(),
+        width,
+        height,
+        format,
+        margin,
+        eccLevel);
     return result;
   }
 
   static Future<CodeResult> processCameraImage(CameraImage image,
       {int format = Format.Any, double cropPercent = 0.5}) async {
-    var isolateData = IsolateData(image, format, cropPercent);
-    CodeResult result = await _inference(isolateData);
+    final IsolateData isolateData = IsolateData(image, format, cropPercent);
+    final CodeResult result = await _inference(isolateData);
     return result;
   }
 
   /// Runs inference in another isolate
   static Future<CodeResult> _inference(IsolateData isolateData) async {
-    ReceivePort responsePort = ReceivePort();
+    final ReceivePort responsePort = ReceivePort();
     isolateUtils?.sendPort
         ?.send(isolateData..responsePort = responsePort.sendPort);
-    var results = await responsePort.first;
+    // TODO: fix below warning from lint
+    // ignore: always_specify_types
+    final results = await responsePort.first;
     return results;
   }
 
@@ -153,7 +162,7 @@ DynamicLibrary _openDynamicLibrary() {
   if (Platform.isAndroid) {
     return DynamicLibrary.open('libflutter_zxing.so');
   } else if (Platform.isWindows) {
-    return DynamicLibrary.open("flutter_zxing_windows_plugin.dll");
+    return DynamicLibrary.open('flutter_zxing_windows_plugin.dll');
   }
   return DynamicLibrary.process();
 }
@@ -163,8 +172,8 @@ DynamicLibrary dylib = _openDynamicLibrary();
 extension Uint8ListBlobConversion on Uint8List {
   /// Allocates a pointer filled with the Uint8List data.
   Pointer<Char> allocatePointer() {
-    final blob = calloc<Int8>(length);
-    final blobBytes = blob.asTypedList(length);
+    final Pointer<Int8> blob = calloc<Int8>(length);
+    final Int8List blobBytes = blob.asTypedList(length);
     blobBytes.setAll(0, this);
     return blob.cast<Char>();
   }
@@ -189,7 +198,7 @@ extension EncodeExt on EncodeResult {
 extension CodeFormat on Format {
   String get name => _formatNames[this] ?? 'Unknown';
 
-  static final writerFormats = [
+  static final List<int> writerFormats = <int>[
     Format.QRCode,
     Format.DataMatrix,
     Format.Aztec,
@@ -209,7 +218,7 @@ extension CodeFormat on Format {
   ];
 }
 
-final _formatNames = {
+final Map<int, String> _formatNames = <int, String>{
   Format.None: 'None',
   Format.Aztec: 'Aztec',
   Format.Codabar: 'CodaBar',

lib/image_converter.dart

@@ -17,7 +17,7 @@ Future<Uint8List> convertImage(CameraImage image) async {
     }
     return img.getBytes(format: imglib.Format.luminance);
   } catch (e) {
-    debugPrint(">>>>>>>>>>>> ERROR: $e");
+    debugPrint('>>>>>>>>>>>> ERROR: $e');
   }
   return Uint8List(0);
 }
@@ -33,21 +33,25 @@ imglib.Image convertBGRA8888(CameraImage image) {
 
 // ignore: unused_element
 imglib.Image convertYUV420(CameraImage image) {
-  var img = imglib.Image(image.width, image.height); // Create Image buffer
+  final imglib.Image img =
+      imglib.Image(image.width, image.height); // Create Image buffer
 
-  Plane plane = image.planes[0];
-  const int shift = (0xFF << 24);
+  final Plane plane = image.planes[0];
+  const int shift = 0xFF << 24;
 
   // Fill image buffer with plane[0] from YUV420_888
   for (int x = 0; x < image.width; x++) {
     for (int planeOffset = 0;
         planeOffset < image.height * image.width;
         planeOffset += image.width) {
+      // TODO: fix below warning from lint
+      // ignore: always_specify_types
       final pixelColor = plane.bytes[planeOffset + x];
       // color: 0x FF  FF  FF  FF
       //           A   B   G   R
       // Calculate pixel color
-      var newVal = shift | (pixelColor << 16) | (pixelColor << 8) | pixelColor;
+      final int newVal =
+          shift | (pixelColor << 16) | (pixelColor << 8) | pixelColor;
 
       img.data[planeOffset + x] = newVal;
     }

lib/isolate_utils.dart

@@ -1,5 +1,6 @@
 import 'dart:isolate';
 import 'dart:math';
+import 'dart:typed_data';
 
 import 'package:camera/camera.dart';
 
@@ -9,26 +10,25 @@ import 'flutter_zxing.dart';
 
 /// Bundles data to pass between Isolate
 class IsolateData {
-  CameraImage cameraImage;
-  int format;
-  double cropPercent;
-
-  SendPort? responsePort;
-
   IsolateData(
     this.cameraImage,
     this.format,
     this.cropPercent,
   );
+  CameraImage cameraImage;
+  int format;
+  double cropPercent;
+
+  SendPort? responsePort;
 }
 
 /// Manages separate Isolate instance for inference
 class IsolateUtils {
-  static const String kDebugName = "ZxingIsolate";
+  static const String kDebugName = 'ZxingIsolate';
 
   // ignore: unused_field
   Isolate? _isolate;
-  final _receivePort = ReceivePort();
+  final ReceivePort _receivePort = ReceivePort();
   SendPort? _sendPort;
 
   SendPort? get sendPort => _sendPort;
@@ -49,21 +49,26 @@ class IsolateUtils {
     _sendPort = null;
   }
 
-  static void readBarcodeEntryPoint(SendPort sendPort) async {
-    final port = ReceivePort();
+  static Future<void> readBarcodeEntryPoint(SendPort sendPort) async {
+    final ReceivePort port = ReceivePort();
     sendPort.send(port.sendPort);
 
     await for (final IsolateData? isolateData in port) {
       if (isolateData != null) {
         try {
-          final image = isolateData.cameraImage;
-          final cropPercent = isolateData.cropPercent;
-          final bytes = await convertImage(image);
-          final cropSize =
+          final CameraImage image = isolateData.cameraImage;
+          final double cropPercent = isolateData.cropPercent;
+          final Uint8List bytes = await convertImage(image);
+          final int cropSize =
               (min(image.width, image.height) * cropPercent).round();
 
-          final result = FlutterZxing.readBarcode(bytes, isolateData.format,
-              image.width, image.height, cropSize, cropSize);
+          final CodeResult result = FlutterZxing.readBarcode(
+              bytes,
+              isolateData.format,
+              image.width,
+              image.height,
+              cropSize,
+              cropSize);
 
           isolateData.responsePort?.send(result);
         } catch (e) {

lib/reader_widget.dart

@@ -12,7 +12,7 @@ import 'isolate_utils.dart';
 
 class ReaderWidget extends StatefulWidget {
   const ReaderWidget({
-    Key? key,
+    super.key,
     required this.onScan,
     this.onControllerCreated,
     this.codeFormat = Format.Any,
@@ -24,7 +24,7 @@ class ReaderWidget extends StatefulWidget {
     this.scanDelay = const Duration(milliseconds: 1000), // 1000ms delay
     this.cropPercent = 0.5, // 50% of the screen
     this.resolution = ResolutionPreset.high,
-  }) : super(key: key);
+  });
 
   final Function(CodeResult) onScan;
   final Function(CameraController?)? onControllerCreated;
@@ -46,7 +46,7 @@ class _ReaderWidgetState extends State<ReaderWidget>
     with TickerProviderStateMixin {
   List<CameraDescription>? cameras;
   CameraController? controller;
-  var _cameraOn = false;
+  bool _cameraOn = false;
 
   double _zoom = 1.0;
   double _scaleFactor = 1.0;
@@ -68,11 +68,11 @@ class _ReaderWidgetState extends State<ReaderWidget>
     initStateAsync();
   }
 
-  void initStateAsync() async {
+  Future<void> initStateAsync() async {
     // Spawn a new isolate
     await FlutterZxing.startCameraProcessing();
 
-    availableCameras().then((cameras) {
+    availableCameras().then((List<CameraDescription> cameras) {
       setState(() {
         this.cameras = cameras;
         if (cameras.isNotEmpty) {
@@ -81,7 +81,7 @@ class _ReaderWidgetState extends State<ReaderWidget>
       });
     });
 
-    SystemChannels.lifecycle.setMessageHandler((message) async {
+    SystemChannels.lifecycle.setMessageHandler((String? message) async {
       debugPrint(message);
       final CameraController? cameraController = controller;
       if (cameraController == null || !cameraController.value.isInitialized) {
@@ -110,7 +110,7 @@ class _ReaderWidgetState extends State<ReaderWidget>
     super.dispose();
   }
 
-  void onNewCameraSelected(CameraDescription cameraDescription) async {
+  Future<void> onNewCameraSelected(CameraDescription cameraDescription) async {
     if (controller != null) {
       await controller!.dispose();
     }
@@ -137,7 +137,9 @@ class _ReaderWidgetState extends State<ReaderWidget>
     }
 
     cameraController.addListener(() {
-      if (mounted) setState(() {});
+      if (mounted) {
+        setState(() {});
+      }
     });
 
     if (mounted) {
@@ -148,11 +150,11 @@ class _ReaderWidgetState extends State<ReaderWidget>
     widget.onControllerCreated?.call(cameraController);
   }
 
-  processCameraImage(CameraImage image) async {
+  Future<void> processCameraImage(CameraImage image) async {
     if (!_isProcessing) {
       _isProcessing = true;
       try {
-        CodeResult result = await FlutterZxing.processCameraImage(
+        final CodeResult result = await FlutterZxing.processCameraImage(
           image,
           format: widget.codeFormat,
           cropPercent: widget.cropPercent,
@@ -163,28 +165,30 @@ class _ReaderWidgetState extends State<ReaderWidget>
           }
           widget.onScan(result);
           setState(() {});
-          await Future.delayed(const Duration(seconds: 1));
+          await Future<void>.delayed(const Duration(seconds: 1));
         }
       } on FileSystemException catch (e) {
         debugPrint(e.message);
       } catch (e) {
         debugPrint(e.toString());
       }
-      await Future.delayed(widget.scanDelay);
+      await Future<void>.delayed(widget.scanDelay);
       _isProcessing = false;
     }
 
-    return null;
+    return;
   }
 
   @override
   Widget build(BuildContext context) {
-    final size = MediaQuery.of(context).size;
-    final cropSize = min(size.width, size.height) * widget.cropPercent;
+    final Size size = MediaQuery.of(context).size;
+    final double cropSize = min(size.width, size.height) * widget.cropPercent;
     return Stack(
-      children: [
+      children: <Widget>[
         // Camera preview
-        Center(child: _cameraPreviewWidget(cropSize)),
+        Center(
+          child: _cameraPreviewWidget(cropSize),
+        ),
       ],
     );
   }
@@ -192,23 +196,22 @@ class _ReaderWidgetState extends State<ReaderWidget>
   // Display the preview from the camera.
   Widget _cameraPreviewWidget(double cropSize) {
     final CameraController? cameraController = controller;
-    if (cameras != null && cameras?.isEmpty == true) {
+    if (cameras != null && (cameras?.isEmpty ?? false)) {
       return const Text('No cameras found');
     } else if (cameraController == null ||
         !cameraController.value.isInitialized ||
         !_cameraOn) {
       return const CircularProgressIndicator();
     } else {
-      final size = MediaQuery.of(context).size;
-      var cameraMaxSize = max(size.width, size.height);
+      final Size size = MediaQuery.of(context).size;
+      final double cameraMaxSize = max(size.width, size.height);
       return Stack(
-        children: [
+        children: <Widget>[
           SizedBox(
             width: cameraMaxSize,
             height: cameraMaxSize,
             child: ClipRRect(
               child: OverflowBox(
-                alignment: Alignment.center,
                 child: FittedBox(
                   fit: BoxFit.cover,
                   child: SizedBox(
@@ -237,10 +240,10 @@ class _ReaderWidgetState extends State<ReaderWidget>
             ),
           if (widget.allowPinchZoom)
             GestureDetector(
-              onScaleStart: (details) {
+              onScaleStart: (ScaleStartDetails details) {
                 _zoom = _scaleFactor;
               },
-              onScaleUpdate: (details) {
+              onScaleUpdate: (ScaleUpdateDetails details) {
                 _scaleFactor =
                     (_zoom * details.scale).clamp(_minZoomLevel, _maxZoomLevel);
                 cameraController.setZoomLevel(_scaleFactor);
@@ -253,14 +256,10 @@ class _ReaderWidgetState extends State<ReaderWidget>
               child: FloatingActionButton(
                 onPressed: () {
                   FlashMode mode = cameraController.value.flashMode;
-                  switch (mode) {
-                    case FlashMode.torch:
-                      mode = FlashMode.off;
-                      break;
-                    case FlashMode.off:
-                      mode = FlashMode.torch;
-                      break;
-                    default:
+                  if (mode == FlashMode.torch) {
+                    mode = FlashMode.off;
+                  } else {
+                    mode = FlashMode.torch;
                   }
                   cameraController.setFlashMode(mode);
                   setState(() {});
@@ -281,8 +280,10 @@ class _ReaderWidgetState extends State<ReaderWidget>
         return Icons.flash_on;
       case FlashMode.off:
         return Icons.flash_off;
-      default:
-        return Icons.flash_off;
+      case FlashMode.always:
+        return Icons.flash_on;
+      case FlashMode.auto:
+        return Icons.flash_auto;
     }
   }
 }

lib/scanner_overlay.dart

@@ -54,31 +54,32 @@ class ScannerOverlay extends ShapeBorder {
 
   @override
   void paint(Canvas canvas, Rect rect, {TextDirection? textDirection}) {
-    final width = rect.width;
-    final borderWidthSize = width / 2;
-    final height = rect.height;
-    final borderOffset = borderWidth / 2;
-    final newBorderLength = borderLength > cutOutSize / 2 + borderWidth * 2
-        ? borderWidthSize / 2
-        : borderLength;
-    final newCutOutSize =
+    final double width = rect.width;
+    final double borderWidthSize = width / 2;
+    final double height = rect.height;
+    final double borderOffset = borderWidth / 2;
+    final double newBorderLength =
+        borderLength > cutOutSize / 2 + borderWidth * 2
+            ? borderWidthSize / 2
+            : borderLength;
+    final double newCutOutSize =
         cutOutSize < width ? cutOutSize : width - borderOffset;
 
-    final backgroundPaint = Paint()
+    final Paint backgroundPaint = Paint()
       ..color = overlayColor
       ..style = PaintingStyle.fill;
 
-    final borderPaint = Paint()
+    final Paint borderPaint = Paint()
       ..color = borderColor
       ..style = PaintingStyle.stroke
       ..strokeWidth = borderWidth;
 
-    final boxPaint = Paint()
+    final Paint boxPaint = Paint()
       ..color = borderColor
       ..style = PaintingStyle.fill
       ..blendMode = BlendMode.dstOut;
 
-    final cutOutRect = Rect.fromLTWH(
+    final Rect cutOutRect = Rect.fromLTWH(
       rect.left + width / 2 - newCutOutSize / 2 + borderOffset,
       rect.top + height / 2 - newCutOutSize / 2 + borderOffset,
       newCutOutSize - borderOffset * 2,

lib/writer_widget.dart

@@ -7,10 +7,10 @@ import 'flutter_zxing.dart';
 
 class WriterWidget extends StatefulWidget {
   const WriterWidget({
-    Key? key,
+    super.key,
     this.onSuccess,
     this.onError,
-  }) : super(key: key);
+  });
 
   final Function(EncodeResult, Uint8List?)? onSuccess;
   final Function(String)? onError;
@@ -24,18 +24,18 @@ class _WriterWidgetState extends State<WriterWidget>
   final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
   final TextEditingController _textController = TextEditingController();
   final TextEditingController _widthController =
-      TextEditingController(text: "300");
+      TextEditingController(text: '300');
   final TextEditingController _heightController =
-      TextEditingController(text: "300");
+      TextEditingController(text: '300');
   final TextEditingController _marginController =
-      TextEditingController(text: "10");
-  final TextEditingController _eccController = TextEditingController(text: "0");
+      TextEditingController(text: '10');
+  final TextEditingController _eccController = TextEditingController(text: '0');
 
   bool isAndroid() => Theme.of(context).platform == TargetPlatform.android;
 
-  final _maxTextLength = 2000;
-  final _supportedFormats = CodeFormat.writerFormats;
-  var _codeFormat = Format.QRCode;
+  final int _maxTextLength = 2000;
+  final List<int> _supportedFormats = CodeFormat.writerFormats;
+  int _codeFormat = Format.QRCode;
 
   @override
   Widget build(BuildContext context) {
@@ -47,7 +47,7 @@ class _WriterWidgetState extends State<WriterWidget>
           child: Column(
             mainAxisSize: MainAxisSize.min,
             mainAxisAlignment: MainAxisAlignment.spaceEvenly,
-            children: [
+            children: <Widget>[
               const SizedBox(height: 20),
               // Input multiline text
               TextFormField(
@@ -55,7 +55,7 @@ class _WriterWidgetState extends State<WriterWidget>
                 keyboardType: TextInputType.multiline,
                 maxLines: null,
                 maxLength: _maxTextLength,
-                onChanged: (value) {
+                onChanged: (String value) {
                   setState(() {});
                 },
                 decoration: InputDecoration(
@@ -65,8 +65,8 @@ class _WriterWidgetState extends State<WriterWidget>
                   counterText:
                       '${_textController.value.text.length} / $_maxTextLength',
                 ),
-                validator: (value) {
-                  if (value?.isEmpty == true) {
+                validator: (String? value) {
+                  if (value?.isEmpty ?? false) {
                     return 'Please enter some text';
                   }
                   return null;
@@ -77,12 +77,12 @@ class _WriterWidgetState extends State<WriterWidget>
               DropdownButtonFormField<int>(
                 value: _codeFormat,
                 items: _supportedFormats
-                    .map((format) => DropdownMenuItem(
+                    .map((int format) => DropdownMenuItem<int>(
                           value: format,
                           child: Text(FlutterZxing.formatName(format)),
                         ))
                     .toList(),
-                onChanged: (format) {
+                onChanged: (int? format) {
                   setState(() {
                     _codeFormat = format ?? Format.QRCode;
                   });
@@ -90,7 +90,7 @@ class _WriterWidgetState extends State<WriterWidget>
               ),
               const SizedBox(height: 20),
               Row(
-                children: [
+                children: <Widget>[
                   Flexible(
                     child: TextFormField(
                       controller: _widthController,
@@ -98,8 +98,8 @@ class _WriterWidgetState extends State<WriterWidget>
                       decoration: const InputDecoration(
                         labelText: 'Width',
                       ),
-                      validator: (value) {
-                        final width = int.tryParse(value ?? '');
+                      validator: (String? value) {
+                        final int? width = int.tryParse(value ?? '');
                         if (width == null) {
                           return 'Invalid number';
                         }
@@ -115,8 +115,8 @@ class _WriterWidgetState extends State<WriterWidget>
                       decoration: const InputDecoration(
                         labelText: 'Height',
                       ),
-                      validator: (value) {
-                        final width = int.tryParse(value ?? '');
+                      validator: (String? value) {
+                        final int? width = int.tryParse(value ?? '');
                         if (width == null) {
                           return 'Invalid number';
                         }
@@ -128,7 +128,7 @@ class _WriterWidgetState extends State<WriterWidget>
               ),
               const SizedBox(height: 20),
               Row(
-                children: [
+                children: <Widget>[
                   Flexible(
                     child: TextFormField(
                       controller: _marginController,
@@ -136,8 +136,8 @@ class _WriterWidgetState extends State<WriterWidget>
                       decoration: const InputDecoration(
                         labelText: 'Margin',
                       ),
-                      validator: (value) {
-                        final width = int.tryParse(value ?? '');
+                      validator: (String? value) {
+                        final int? width = int.tryParse(value ?? '');
                         if (width == null) {
                           return 'Invalid number';
                         }
@@ -153,8 +153,8 @@ class _WriterWidgetState extends State<WriterWidget>
                       decoration: const InputDecoration(
                         labelText: 'ECC Level',
                       ),
-                      validator: (value) {
-                        final width = int.tryParse(value ?? '');
+                      validator: (String? value) {
+                        final int? width = int.tryParse(value ?? '');
                         if (width == null) {
                           return 'Invalid number';
                         }
@@ -182,18 +182,24 @@ class _WriterWidgetState extends State<WriterWidget>
     if (_formKey.currentState?.validate() ?? false) {
       _formKey.currentState?.save();
       FocusScope.of(context).unfocus();
-      final text = _textController.value.text;
-      final width = int.parse(_widthController.value.text);
-      final height = int.parse(_heightController.value.text);
-      final margin = int.parse(_marginController.value.text);
-      final ecc = int.parse(_eccController.value.text);
-      var result = FlutterZxing.encodeBarcode(
+      final String text = _textController.value.text;
+      final int width = int.parse(_widthController.value.text);
+      final int height = int.parse(_heightController.value.text);
+      final int margin = int.parse(_marginController.value.text);
+      final int ecc = int.parse(_eccController.value.text);
+      final EncodeResult result = FlutterZxing.encodeBarcode(
           text, width, height, _codeFormat, margin, ecc);
       String? error;
       if (result.isValidBool) {
         try {
-          final img = imglib.Image.fromBytes(width, height, result.bytes);
-          final encodedBytes = Uint8List.fromList(imglib.encodeJpg(img));
+          final imglib.Image img = imglib.Image.fromBytes(
+            width,
+            height,
+            result.bytes,
+          );
+          final Uint8List encodedBytes = Uint8List.fromList(
+            imglib.encodeJpg(img),
+          );
           widget.onSuccess?.call(result, encodedBytes);
         } catch (e) {
           error = e.toString();

zxscanner/pubspec.lock

@@ -35,7 +35,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.8.2"
+    version: "2.9.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -300,7 +300,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.3.1"
+    version: "0.3.2"
   font_awesome_flutter:
     dependency: "direct main"
     description: