feat: null safety

Author: Gordon Hayes

section_2/built_in_explicit_animations/lib/main.dart

@@ -9,7 +9,7 @@ import 'package:transition_widgets_example/transitions.dart/slide_transition.dar
 void main() => runApp(const MyApp());
 
 class MyApp extends StatelessWidget {
-  const MyApp({Key key}) : super(key: key);
+  const MyApp({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

section_2/built_in_explicit_animations/lib/transitions.dart/align_transition.dart

@@ -2,19 +2,20 @@ import 'package:flutter/material.dart';
 import 'package:transition_widgets_example/styles.dart';
 
 class AlignTransitionExample extends StatefulWidget {
-  const AlignTransitionExample({Key key}) : super(key: key);
+  const AlignTransitionExample({Key? key}) : super(key: key);
 
   @override
   _AlignTransitionExampleState createState() => _AlignTransitionExampleState();
 }
 
 class _AlignTransitionExampleState extends State<AlignTransitionExample>
     with SingleTickerProviderStateMixin {
-  AnimationController _controller;
-  Animation<AlignmentGeometry> _animation;
+  late AnimationController _controller;
+  late Animation<AlignmentGeometry> _animation;
 
   @override
   void initState() {
+    super.initState();
     _controller = AnimationController(
       vsync: this,
       duration: const Duration(seconds: 2),
@@ -24,7 +25,6 @@ class _AlignTransitionExampleState extends State<AlignTransitionExample>
         .chain(CurveTween(curve: Curves.bounceOut))
         .animate(_controller);
     _controller.repeat(reverse: true);
-    super.initState();
   }
 
   @override

section_2/built_in_explicit_animations/lib/transitions.dart/fade_transition.dart

@@ -1,27 +1,27 @@
 import 'package:flutter/material.dart';
 
 class FadeTransitionExample extends StatefulWidget {
-  const FadeTransitionExample({Key key}) : super(key: key);
+  const FadeTransitionExample({Key? key}) : super(key: key);
 
   @override
   _FadeTransitionExampleState createState() => _FadeTransitionExampleState();
 }
 
 class _FadeTransitionExampleState extends State<FadeTransitionExample>
     with SingleTickerProviderStateMixin {
-  AnimationController _controller;
+  late AnimationController _controller;
 
   String _text = 'Fade In';
   String _key = 'fadein';
 
   @override
   void initState() {
+    super.initState();
     _controller =
         AnimationController(vsync: this, duration: const Duration(seconds: 5));
     _controller
       ..repeat(reverse: true)
       ..addStatusListener(_animationStatusListener);
-    super.initState();
   }
 
   void _animationStatusListener(AnimationStatus status) {

section_2/built_in_explicit_animations/lib/transitions.dart/rotate_and_scale_transition.dart

@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:transition_widgets_example/styles.dart';
 
 class RotateAndScaleTransitionExample extends StatefulWidget {
-  const RotateAndScaleTransitionExample({Key key}) : super(key: key);
+  const RotateAndScaleTransitionExample({Key? key}) : super(key: key);
 
   @override
   _RotateAndScaleTransitionExampleState createState() =>
@@ -12,13 +12,14 @@ class RotateAndScaleTransitionExample extends StatefulWidget {
 class _RotateAndScaleTransitionExampleState
     extends State<RotateAndScaleTransitionExample>
     with TickerProviderStateMixin {
-  AnimationController _controller;
-  AnimationController _controller2;
-  Animation<double> _rotateAnimation;
-  Animation<double> _scaleAnimation;
+  late AnimationController _controller;
+  late AnimationController _controller2;
+  late Animation<double> _rotateAnimation;
+  late Animation<double> _scaleAnimation;
 
   @override
   void initState() {
+    super.initState();
     _controller = AnimationController(
       vsync: this,
       duration: const Duration(seconds: 3),
@@ -33,12 +34,12 @@ class _RotateAndScaleTransitionExampleState
         .animate(CurvedAnimation(parent: _controller2, curve: Curves.ease));
     _controller.repeat(reverse: true);
     _controller2.forward();
-    super.initState();
   }
 
   @override
   void dispose() {
     _controller.dispose();
+    _controller2.dispose();
     super.dispose();
   }
 

section_2/built_in_explicit_animations/lib/transitions.dart/scale_transition.dart

@@ -3,7 +3,7 @@ import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:transition_widgets_example/styles.dart';
 
 class ScaleTransitionExample extends HookWidget {
-  const ScaleTransitionExample({Key key}) : super(key: key);
+  const ScaleTransitionExample({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

section_2/built_in_explicit_animations/lib/transitions.dart/slide_transition.dart

@@ -1,21 +1,22 @@
 import 'package:flutter/material.dart';
 
 class SlideTransitionExample extends StatefulWidget {
-  const SlideTransitionExample({Key key, this.child}) : super(key: key);
+  const SlideTransitionExample({Key? key, this.child}) : super(key: key);
 
-  final Widget child;
+  final Widget? child;
 
   @override
   _SlideTransitionExampleState createState() => _SlideTransitionExampleState();
 }
 
 class _SlideTransitionExampleState extends State<SlideTransitionExample>
     with SingleTickerProviderStateMixin {
-  AnimationController _controller;
-  Animation<Offset> _animation;
+  late AnimationController _controller;
+  late Animation<Offset> _animation;
 
   @override
   void initState() {
+    super.initState();
     _controller = AnimationController(
       vsync: this,
       duration: const Duration(seconds: 1),
@@ -30,8 +31,6 @@ class _SlideTransitionExampleState extends State<SlideTransitionExample>
       ),
     );
     _controller.forward();
-
-    super.initState();
   }
 
   @override

section_2/built_in_explicit_animations/pubspec.lock

@@ -49,7 +49,7 @@ packages:
       name: cupertino_icons
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.2"
+    version: "1.0.3"
   fake_async:
     dependency: transitive
     description:
@@ -68,7 +68,7 @@ packages:
       name: flutter_hooks
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.7.0"
+    version: "0.18.0"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -165,4 +165,4 @@ packages:
     version: "2.1.2"
 sdks:
   dart: ">=2.12.0 <3.0.0"
-  flutter: ">=1.5.8"
+  flutter: ">=1.20.0"

section_2/built_in_explicit_animations/pubspec.yaml

@@ -14,13 +14,13 @@ description: A new Flutter project.
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
     sdk: flutter
-  cupertino_icons: ^0.1.2
-  flutter_hooks: ^0.7.0
+  cupertino_icons: ^1.0.3
+  flutter_hooks: ^0.18.0
 
 dev_dependencies:
   flutter_test: