Introduce null safety

Author: Kamil Klyta

example/pubspec.lock

@@ -7,42 +7,42 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.2"
+    version: "2.5.0"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0"
   characters:
     dependency: transitive
     description:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.0"
+    version: "1.1.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.3"
+    version: "1.2.0"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.1"
+    version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.13"
+    version: "1.15.0"
   confetti:
     dependency: "direct main"
     description:
@@ -51,7 +51,7 @@ packages:
     source: hosted
     version: "0.4.0"
   custom_refresh_indicator:
-    dependency: "direct dev"
+    dependency: "direct main"
     description:
       path: ".."
       relative: true
@@ -63,7 +63,7 @@ packages:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -80,21 +80,21 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.8"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.0"
   random_color:
     dependency: transitive
     description:
@@ -113,55 +113,55 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.5"
+    version: "1.10.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.17"
+    version: "0.2.19"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
+    version: "2.1.0"
 sdks:
-  dart: ">=2.9.0-14.0.dev <3.0.0"
+  dart: ">=2.12.0-0.0 <3.0.0"

example/pubspec.yaml

@@ -10,12 +10,12 @@ dependencies:
   flutter:
     sdk: flutter
   confetti: 0.4.0
+  custom_refresh_indicator:
+    path: ../
 
 dev_dependencies:
   flutter_test:
     sdk: flutter
-  custom_refresh_indicator:
-    path: ../
 
 flutter:
   uses-material-design: true

lib/src/controller.dart

@@ -61,16 +61,16 @@ class IndicatorController extends ChangeNotifier {
 
   /// Creates [CustomRefreshIndicator] controller class
   factory IndicatorController({
-    bool refreshEnabled,
+    bool? refreshEnabled,
   }) =>
       IndicatorController._(refreshEnabled: refreshEnabled);
 
   IndicatorController._({
-    double value,
-    AxisDirection direction,
-    ScrollDirection scrollingDirection,
-    IndicatorState state,
-    bool refreshEnabled,
+    double? value,
+    AxisDirection? direction,
+    ScrollDirection? scrollingDirection,
+    IndicatorState? state,
+    bool? refreshEnabled,
   })  : _currentState = state ?? IndicatorState.idle,
         _previousState = state ?? IndicatorState.idle,
         _scrollingDirection = scrollingDirection ?? ScrollDirection.idle,
@@ -181,10 +181,10 @@ class IndicatorController extends ChangeNotifier {
   }
 
   /// Returns `true` when state did change [from] to [to].
-  bool didStateChange({IndicatorState from, IndicatorState to}) {
+  bool didStateChange({IndicatorState? from, IndicatorState? to}) {
     final stateChanged = _previousState != _currentState;
-    if (to == null) return _previousState == from && stateChanged;
-    if (from == null) return _currentState == to && stateChanged;
+    if (to == null && from != null) return _previousState == from && stateChanged;
+    if (to != null && from == null ) return _currentState == to && stateChanged;
     if (to == null && from == null) return stateChanged;
     return _previousState == from && _currentState == to;
   }

lib/src/custom_refresh_indicator.dart

@@ -27,7 +27,7 @@ class CustomRefreshIndicator extends StatefulWidget {
   final Duration loadingToIdleDuration;
 
   /// {@macro custom_refresh_indicator.complete_state}
-  final Duration completeStateDuration;
+  final Duration? completeStateDuration;
 
   /// A check that specifies whether a [ScrollNotification] should be
   /// handled by this widget.
@@ -43,11 +43,11 @@ class CustomRefreshIndicator extends StatefulWidget {
   final bool trailingGlowVisible;
 
   /// Number of pixels that user should drag to change [IndicatorState] from idle to armed.
-  final double offsetToArmed;
+  final double? offsetToArmed;
 
   /// Value from 0.0 to 1.0 that describes the percentage of scroll container extent
   /// that user should drag to change [IndicatorState] from idle to armed.
-  final double extentPercentageToArmed;
+  final double? extentPercentageToArmed;
 
   /// Part of widget tree that contains scrollable element (like ListView).
   /// Scroll notifications from the first scrollable element will be used
@@ -79,13 +79,13 @@ class CustomRefreshIndicator extends StatefulWidget {
   /// The indicator controller will be passed as the third argument to the [builder] method.
   ///
   /// To better understand this data, look at example app.
-  final IndicatorController controller;
+  final IndicatorController? controller;
 
   CustomRefreshIndicator({
-    Key key,
-    @required this.child,
-    @required this.onRefresh,
-    @required this.builder,
+    Key? key,
+    required this.child,
+    required this.onRefresh,
+    required this.builder,
     this.notificationPredicate = defaultScrollNotificationPredicate,
     this.controller,
     this.offsetToArmed,
@@ -96,9 +96,7 @@ class CustomRefreshIndicator extends StatefulWidget {
     this.completeStateDuration,
     this.leadingGlowVisible = false,
     this.trailingGlowVisible = true,
-  })  : assert(child != null, '`child` argument cannot be null.'),
-        assert(builder != null, '`builder` argument cannot be null.'),
-        assert(
+  })  : assert(
           extentPercentageToArmed == null || offsetToArmed == null,
           'Providing `extentPercentageToArmed` argument take no effect when `offsetToArmed` is provided. '
           'Remove redundant argument.',
@@ -120,10 +118,10 @@ class _CustomRefreshIndicatorState extends State<CustomRefreshIndicator>
     __canStart = canStart;
   }
 
-  double _dragOffset;
+  late double _dragOffset;
 
-  AnimationController _animationController;
-  IndicatorController _customRefreshIndicatorController;
+  late AnimationController _animationController;
+  late IndicatorController _customRefreshIndicatorController;
 
   /// Current [IndicatorController]
   IndicatorController get controller => _customRefreshIndicatorController;
@@ -157,11 +155,8 @@ class _CustomRefreshIndicatorState extends State<CustomRefreshIndicator>
   }
 
   /// Notifies the listeners of the controller
-  void _updateCustomRefreshIndicatorValue() {
-    _customRefreshIndicatorController._setValue(
-      _animationController?.value ?? _kInitialValue,
-    );
-  }
+  void _updateCustomRefreshIndicatorValue() =>
+      _customRefreshIndicatorController._setValue(_animationController.value);
 
   bool _handleGlowNotification(OverscrollIndicatorNotification notification) {
     if (notification.depth != 0) return false;
@@ -190,7 +185,7 @@ class _CustomRefreshIndicatorState extends State<CustomRefreshIndicator>
       if (notification.metrics.extentBefore > 0.0) {
         _hide();
       } else {
-        _dragOffset -= notification.scrollDelta;
+        _dragOffset -= notification.scrollDelta!;
         _calculateDragOffset(notification.metrics.viewportDimension);
       }
       if (controller.state == IndicatorState.armed &&
@@ -229,10 +224,12 @@ class _CustomRefreshIndicatorState extends State<CustomRefreshIndicator>
 
     double newValue;
 
+    final offsetToArmed = widget.offsetToArmed;
+
     /// If [offestToArmed] is provided then it will be used otherwise
     /// [extentPercentageToArmed]
-    if (widget.offsetToArmed != null) {
-      newValue = _dragOffset / widget.offsetToArmed;
+    if (offsetToArmed != null) {
+      newValue = _dragOffset / offsetToArmed;
     } else {
       final extentPercentageToArmed = widget.extentPercentageToArmed ??
           CustomRefreshIndicator.defaultExtentPercentageToArmed;
@@ -281,9 +278,10 @@ class _CustomRefreshIndicatorState extends State<CustomRefreshIndicator>
     if (!mounted) return;
 
     /// optional complete state
-    if (widget.completeStateDuration != null) {
+    final completeStateDuration = widget.completeStateDuration;
+    if (completeStateDuration != null) {
       controller._setIndicatorState(IndicatorState.complete);
-      await Future.delayed(widget.completeStateDuration);
+      await Future.delayed(completeStateDuration);
     }
 
     if (!mounted) return;