feat: null safety

Author: Gordon Hayes

section_6/routes_and_the_rest/lib/main.dart

@@ -7,7 +7,7 @@ import 'ux/pages/home.dart';
 void main() => runApp(const MyApp());
 
 class MyApp extends StatefulWidget {
-  const MyApp({Key key}) : super(key: key);
+  const MyApp({Key? key}) : super(key: key);
 
   @override
   _MyAppState createState() => _MyAppState();

section_6/routes_and_the_rest/lib/models/content_model.dart

@@ -1,10 +1,10 @@
 class ContentModel {
   const ContentModel({
-    this.title,
-    this.description,
-    this.logoLocation,
-    this.logoTag,
-    this.titleTag,
+    required this.title,
+    required this.description,
+    required this.logoLocation,
+    required this.logoTag,
+    required this.titleTag,
   });
 
   final String title;

section_6/routes_and_the_rest/lib/ux/extensions/bounce_extensions.dart

@@ -9,7 +9,10 @@ extension BounceExtension on Widget {
 }
 
 class _BounceOutAnimation extends StatefulWidget {
-  const _BounceOutAnimation({Key key, this.child}) : super(key: key);
+  const _BounceOutAnimation({
+    Key? key,
+    required this.child,
+  }) : super(key: key);
 
   final Widget child;
 
@@ -19,8 +22,8 @@ class _BounceOutAnimation extends StatefulWidget {
 
 class _BounceOutAnimationState extends State<_BounceOutAnimation>
     with SingleTickerProviderStateMixin {
-  AnimationController _controller;
-  Animation<double> _animation;
+  late AnimationController _controller;
+  late Animation<double> _animation;
 
   static final TweenSequence<double> _offsetTween = TweenSequence(
     <TweenSequenceItem<double>>[
@@ -40,12 +43,13 @@ class _BounceOutAnimationState extends State<_BounceOutAnimation>
 
   @override
   void initState() {
+    super.initState();
+
     _controller =
         AnimationController(vsync: this, duration: const Duration(seconds: 2));
     _animation = _offsetTween.animate(_controller);
 
     _controller.repeat();
-    super.initState();
   }
 
   @override

section_6/routes_and_the_rest/lib/ux/pages/home.dart

@@ -12,7 +12,7 @@ import '../widgets/zoom_page_view.dart';
 import 'learn_more_page.dart';
 
 class Home extends StatefulWidget {
-  const Home({Key key}) : super(key: key);
+  const Home({Key? key}) : super(key: key);
 
   @override
   _HomeState createState() => _HomeState();
@@ -26,19 +26,19 @@ class _HomeState extends State<Home>
 
   final ValueNotifier<double> _valueNotifier = ValueNotifier(0.5);
 
-  PageController _pageController;
-  AnimationController _controller;
+  late PageController _pageController;
+  late AnimationController _controller;
 
   @override
   void initState() {
+    super.initState();
+
     _pageController = PageController(
         initialPage: _initialPage, viewportFraction: _viewPortFraction);
     _controller = AnimationController(
       vsync: this,
       duration: _transitionDuration,
     );
-
-    super.initState();
   }
 
   @override
@@ -120,7 +120,7 @@ class _HomeState extends State<Home>
           children: <Widget>[
             ValueListenableBuilder(
               valueListenable: _valueNotifier,
-              builder: (BuildContext context, double value, Widget child) {
+              builder: (BuildContext context, double value, Widget? child) {
                 return BinarayBackround(value: _valueNotifier.value);
               },
             ),

section_6/routes_and_the_rest/lib/ux/pages/info_page.dart

@@ -7,8 +7,8 @@ import '../styles/styles.dart';
 
 class InfoPage extends StatelessWidget {
   const InfoPage({
-    Key key,
-    @required this.content,
+    Key? key,
+    required this.content,
   }) : super(key: key);
 
   final ContentModel content;

section_6/routes_and_the_rest/lib/ux/pages/learn_more_page.dart

@@ -9,7 +9,7 @@ import '../paint/line_painter.dart';
 import '../styles/styles.dart';
 
 class LearnMorePage extends StatefulWidget {
-  const LearnMorePage({Key key}) : super(key: key);
+  const LearnMorePage({Key? key}) : super(key: key);
 
   @override
   _LearnMorePageState createState() => _LearnMorePageState();
@@ -19,17 +19,17 @@ class _LearnMorePageState extends State<LearnMorePage>
     with SingleTickerProviderStateMixin {
   final ScrollController _scrollController = ScrollController();
 
-  ParticleController _particleController;
-  AnimationController _animationController;
+  late ParticleController _particleController;
+  late AnimationController _animationController;
 
-  double _pixels;
-  int _timestamp;
+  double? _pixels;
+  late int _timestamp;
 
   void _scrollListener() {
     final pixels = _scrollController.position.pixels;
     final timestamp = DateTime.now().millisecondsSinceEpoch;
     if (_pixels != null) {
-      var velocity = ((pixels - _pixels) / (timestamp - _timestamp)) / 100;
+      var velocity = ((pixels - _pixels!) / (timestamp - _timestamp)) / 100;
       if (velocity > 0) {
         velocity = min(velocity, 0.1);
       } else {
@@ -43,6 +43,8 @@ class _LearnMorePageState extends State<LearnMorePage>
 
   @override
   void initState() {
+    super.initState();
+
     _particleController = ParticleController();
     _animationController = AnimationController(
       vsync: this,
@@ -52,14 +54,14 @@ class _LearnMorePageState extends State<LearnMorePage>
     );
     _animationController.repeat();
 
-    // _scrollController.position.
     _scrollController.addListener(_scrollListener);
-    super.initState();
   }
 
   @override
   void dispose() {
     _animationController.dispose();
+    _scrollController.removeListener(_scrollListener);
+
     super.dispose();
   }
 
@@ -135,7 +137,10 @@ class _LearnMorePageState extends State<LearnMorePage>
 }
 
 class LearnMoreHeader extends StatefulWidget {
-  const LearnMoreHeader({Key key, this.visibility = 1}) : super(key: key);
+  const LearnMoreHeader({
+    Key? key,
+    this.visibility = 1,
+  }) : super(key: key);
   final double visibility;
 
   @override
@@ -144,22 +149,23 @@ class LearnMoreHeader extends StatefulWidget {
 
 class _LearnMoreHeaderState extends State<LearnMoreHeader>
     with SingleTickerProviderStateMixin {
-  AnimationController _animationController;
-  CurvedAnimation _animation;
+  late AnimationController _animationController;
+  late CurvedAnimation _animation;
 
   @override
   void initState() {
+    super.initState();
     _animationController =
         AnimationController(vsync: this, duration: const Duration(seconds: 3));
     _animation =
         CurvedAnimation(parent: _animationController, curve: Curves.slowMiddle);
     _animationController.repeat();
-    super.initState();
   }
 
   @override
   void dispose() {
     _animationController.dispose();
+
     super.dispose();
   }
 
@@ -206,11 +212,11 @@ class ParticleController {
   int numberOfParticles;
   List<Particle> particles = [];
 
-  void update({double force}) {
+  void update({double? force}) {
     for (final particle in particles) {
       particle.applyForceUp(force: force);
       if (particle.position.dy < 0.0) {
-        final yPos = 1 + lerpDouble(0.1, 0.3, random.nextDouble());
+        final yPos = 1 + lerpDouble(0.1, 0.3, random.nextDouble())!;
         particle.reset(y: yPos);
       }
     }
@@ -222,10 +228,10 @@ class Particle {
     _init();
   }
 
-  Offset _position;
-  double radius;
-  Paint paint;
-  double _force;
+  late Offset _position;
+  late double radius;
+  late Paint paint;
+  double? _force;
 
   final Random random;
 
@@ -240,19 +246,19 @@ class Particle {
     _force = _randomForce();
   }
 
-  void applyForceUp({double force}) {
-    final newForce = _force + (force ?? 0);
+  void applyForceUp({double? force}) {
+    final newForce = (_force ?? 0) + (force ?? 0);
     _position += Offset(0, -newForce);
   }
 
-  void reset({double y}) {
+  void reset({double? y}) {
     y ??= random.nextDouble();
     _position = Offset(random.nextDouble(), y);
     _force = _randomForce();
   }
 
   double _randomForce() {
-    return lerpDouble(0.001, 0.005, random.nextDouble());
+    return lerpDouble(0.001, 0.005, random.nextDouble())!;
   }
 }
 
@@ -275,11 +281,11 @@ class ParticlePainter extends CustomPainter {
   }
 }
 
-class LearnMoreSliverDelegateHeader implements SliverPersistentHeaderDelegate {
+class LearnMoreSliverDelegateHeader extends SliverPersistentHeaderDelegate {
   LearnMoreSliverDelegateHeader({
-    @required this.minExtent,
-    @required this.maxExtent,
-    this.onDownPressed,
+    required this.minExtent,
+    required this.maxExtent,
+    required this.onDownPressed,
   });
 
   @override
@@ -326,17 +332,8 @@ class LearnMoreSliverDelegateHeader implements SliverPersistentHeaderDelegate {
   }
 
   @override
-  FloatingHeaderSnapConfiguration get snapConfiguration => null;
-
-  @override
-  OverScrollHeaderStretchConfiguration get stretchConfiguration => null;
-
-  @override
-  // TODO: implement showOnScreenConfiguration
-  PersistentHeaderShowOnScreenConfiguration get showOnScreenConfiguration =>
-      null;
+  FloatingHeaderSnapConfiguration? get snapConfiguration => null;
 
   @override
-  // TODO: implement vsync
-  TickerProvider get vsync => null;
+  OverScrollHeaderStretchConfiguration? get stretchConfiguration => null;
 }

section_6/routes_and_the_rest/lib/ux/transitions/flip_transition.dart

@@ -5,9 +5,9 @@ import 'package:flutter/material.dart';
 
 class FlipTransition extends AnimatedWidget {
   FlipTransition({
-    Key key,
-    Animation<double> animation,
-    this.child,
+    Key? key,
+    required Animation<double> animation,
+    required this.child,
     bool isEntry = true,
   })  : offsetXTween = Tween<double>(begin: isEntry ? -15 : 15, end: 2),
         scaleSequence = TweenSequence(
@@ -135,8 +135,11 @@ class FlipTransition extends AnimatedWidget {
 }
 
 class RotationY extends StatelessWidget {
-  const RotationY({Key key, @required this.child, this.rotationY = 0})
-      : super(key: key);
+  const RotationY({
+    Key? key,
+    required this.child,
+    this.rotationY = 0,
+  }) : super(key: key);
 
   //Degrees to rads constant
   static const double degrees2Radians = pi / 180;

section_6/routes_and_the_rest/lib/ux/widgets/binary_background.dart

@@ -4,8 +4,8 @@ import '../styles/styles.dart';
 
 class BinarayBackround extends StatelessWidget {
   const BinarayBackround({
-    Key key,
-    @required this.value,
+    Key? key,
+    required this.value,
   }) : super(key: key);
 
   final double value;
@@ -26,7 +26,7 @@ class BinarayBackround extends StatelessWidget {
               const Alignment(-0.9, 0),
               const Alignment(0.9, 0),
               value,
-            ),
+            )!,
             fit: BoxFit.cover,
           ),
         ),

section_6/routes_and_the_rest/lib/ux/widgets/learn_more_button/learn_more_button.dart

@@ -8,7 +8,10 @@ import 'wiggle_painter.dart';
 import 'wiggle_path.dart';
 
 class LearnMoreButton extends StatefulWidget {
-  const LearnMoreButton({Key key, this.onPressed}) : super(key: key);
+  const LearnMoreButton({
+    Key? key,
+    required this.onPressed,
+  }) : super(key: key);
 
   final VoidCallback onPressed;
 
@@ -18,15 +21,17 @@ class LearnMoreButton extends StatefulWidget {
 
 class _LearnMoreButtonState extends State<LearnMoreButton>
     with SingleTickerProviderStateMixin {
-  WigglePath _wigglePath;
-  AnimationController _controller;
-  Animation<double> _animation;
+  late WigglePath _wigglePath;
+  late AnimationController _controller;
+  late Animation<double> _animation;
 
   static const buttonWidth = 300.0;
   static const buttonHeight = 200.0;
 
   @override
   void initState() {
+    super.initState();
+
     _wigglePath = WigglePath(width: buttonWidth, height: buttonHeight);
     _controller =
         AnimationController(vsync: this, duration: const Duration(seconds: 5));
@@ -39,7 +44,13 @@ class _LearnMoreButtonState extends State<LearnMoreButton>
           _controller.forward(from: 0);
         }
       });
-    super.initState();
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+
+    super.dispose();
   }
 
   @override