feat: null safety

Author: Gordon Hayes

section_4/login_example_sequence_animation/lib/main.dart

@@ -5,7 +5,7 @@ import 'pages/auth_page.dart';
 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_4/login_example_sequence_animation/lib/pages/auth_page.dart

@@ -18,7 +18,7 @@ enum AuthState {
 }
 
 class AuthPage extends StatefulWidget {
-  const AuthPage({Key key}) : super(key: key);
+  const AuthPage({Key? key}) : super(key: key);
 
   @override
   _AuthPageState createState() => _AuthPageState();
@@ -27,8 +27,8 @@ class AuthPage extends StatefulWidget {
 class _AuthPageState extends State<AuthPage>
     with SingleTickerProviderStateMixin {
   // animation variables
-  AnimationController _controller;
-  SequenceAnimation _sequenceAnimation;
+  late AnimationController _controller;
+  late SequenceAnimation _sequenceAnimation;
 
   // variables to control the transition effect to the home page
   double _expandingWidth = 0;
@@ -47,15 +47,15 @@ class _AuthPageState extends State<AuthPage>
 
   @override
   void initState() {
+    super.initState();
+
     _controller = AnimationController(
       vsync: this,
       duration: const Duration(milliseconds: 1200),
     )..addStatusListener(_animationStatusListener);
 
     _initSequenceAnimation();
     _controller.forward(from: 0);
-
-    super.initState();
   }
 
   @override
@@ -211,7 +211,7 @@ class _AuthPageState extends State<AuthPage>
                       decoration: BoxDecoration(
                         color: Colors.grey.shade300.withOpacity(0.1),
                         borderRadius: _sequenceAnimation['borderRadius'].value
-                            as BorderRadiusGeometry,
+                            as BorderRadiusGeometry?,
                       ),
                       child: Stack(
                         children: <Widget>[

section_4/login_example_sequence_animation/lib/pages/home_page.dart

@@ -3,7 +3,7 @@ import 'package:flutter/material.dart';
 import '../styles/backgrounds.dart';
 
 class HomePage extends StatefulWidget {
-  const HomePage({Key key}) : super(key: key);
+  const HomePage({Key? key}) : super(key: key);
 
   @override
   _HomePageState createState() => _HomePageState();
@@ -22,13 +22,13 @@ class _HomePageState extends State<HomePage> {
           children: <Widget>[
             Text(
               'Success!',
-              style: Theme.of(context).textTheme.headline4.copyWith(
+              style: Theme.of(context).textTheme.headline4!.copyWith(
                     color: Colors.white,
                   ),
             ),
             Text(
               'This is the home page',
-              style: Theme.of(context).textTheme.headline6.copyWith(
+              style: Theme.of(context).textTheme.headline6!.copyWith(
                     color: Colors.white,
                   ),
             ),

section_4/login_example_sequence_animation/lib/styles/backgrounds.dart

@@ -9,9 +9,9 @@ BoxDecoration backgroundAuthDecoration() {
       end: Alignment.topRight,
       stops: const [0.1, 0.5, 0.9],
       colors: [
-        authPageBackgroundColor[700],
-        authPageBackgroundColor[600],
-        authPageBackgroundColor[400],
+        authPageBackgroundColor[700]!,
+        authPageBackgroundColor[600]!,
+        authPageBackgroundColor[400]!,
       ],
     ),
   );
@@ -27,10 +27,10 @@ LinearGradient linearGradientHomeDecoration() {
     end: Alignment.topRight,
     stops: const [0.1, 0.5, 0.7, 0.9],
     colors: [
-      homePageBackgroundColor[800],
-      homePageBackgroundColor[700],
-      homePageBackgroundColor[600],
-      homePageBackgroundColor[400],
+      homePageBackgroundColor[800]!,
+      homePageBackgroundColor[700]!,
+      homePageBackgroundColor[600]!,
+      homePageBackgroundColor[400]!,
     ],
   );
 }

section_4/login_example_sequence_animation/lib/utils/fade_route.dart

@@ -6,10 +6,10 @@ class FadeRoute extends PageRoute<dynamic> {
   final Widget child;
 
   @override
-  Color get barrierColor => null;
+  Color? get barrierColor => null;
 
   @override
-  String get barrierLabel => null;
+  String? get barrierLabel => null;
 
   @override
   Widget buildPage(BuildContext context, Animation<double> animation,

section_4/login_example_sequence_animation/lib/widgets/expanding_page_animation.dart

@@ -4,10 +4,10 @@ import '../styles/backgrounds.dart';
 
 class ExpandingPageAnimation extends StatelessWidget {
   const ExpandingPageAnimation({
-    Key key,
-    @required double width,
-    @required double height,
-    @required double borderRadius,
+    Key? key,
+    required double width,
+    required double height,
+    required double borderRadius,
   })  : _width = width,
         _height = height,
         _borderRadius = borderRadius,

section_4/login_example_sequence_animation/lib/widgets/forms/call_to_action_button.dart

@@ -2,12 +2,11 @@ import 'package:flutter/material.dart';
 
 class CallToActionButton extends StatelessWidget {
   const CallToActionButton({
-    Key key,
-    @required this.onPressed,
-    @required this.text,
-    @required this.color,
-  })  : assert(onPressed != null),
-        super(key: key);
+    Key? key,
+    required this.onPressed,
+    required this.text,
+    required this.color,
+  }) : super(key: key);
 
   final VoidCallback onPressed;
   final String text;
@@ -16,11 +15,7 @@ class CallToActionButton extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return TextButton(
-      onPressed: () {
-        if (onPressed != null) {
-          onPressed();
-        }
-      },
+      onPressed: onPressed,
       child: Text(text, style: TextStyle(color: color, fontSize: 16)),
     );
   }

section_4/login_example_sequence_animation/lib/widgets/forms/call_to_action_text.dart

@@ -1,15 +1,17 @@
 import 'package:flutter/material.dart';
 
 class CallToActionText extends StatelessWidget {
-  const CallToActionText(this.text, {Key key}) : super(key: key);
+  const CallToActionText(this.text, {Key? key}) : super(key: key);
 
   final String text;
   @override
   Widget build(BuildContext context) {
     return Text(
       text,
-      style:
-          Theme.of(context).textTheme.subtitle1.copyWith(color: Colors.white70),
+      style: Theme.of(context)
+          .textTheme
+          .subtitle1!
+          .copyWith(color: Colors.white70),
     );
   }
 }

section_4/login_example_sequence_animation/lib/widgets/forms/login_form.dart

@@ -7,10 +7,10 @@ import 'text_input_box.dart';
 
 class LoginForm extends StatelessWidget {
   const LoginForm({
-    Key key,
-    @required this.onLoginPressed,
-    @required this.onSignUpPressed,
-    @required this.safeArea,
+    Key? key,
+    required this.onLoginPressed,
+    required this.onSignUpPressed,
+    required this.safeArea,
   }) : super(key: key);
 
   final VoidCallback onSignUpPressed;

section_4/login_example_sequence_animation/lib/widgets/forms/signup_form.dart

@@ -6,12 +6,12 @@ import 'call_to_action_text.dart';
 import 'text_input_box.dart';
 
 class SignUpForm extends StatelessWidget {
-  const SignUpForm(
-      {Key key,
-      @required this.onLoginPressed,
-      @required this.onSignUpPressed,
-      @required this.safeArea})
-      : super(key: key);
+  const SignUpForm({
+    Key? key,
+    required this.onLoginPressed,
+    required this.onSignUpPressed,
+    required this.safeArea,
+  }) : super(key: key);
 
   final VoidCallback onLoginPressed;
   final VoidCallback onSignUpPressed;

section_4/login_example_sequence_animation/lib/widgets/forms/text_input_box.dart

@@ -2,9 +2,9 @@ import 'package:flutter/material.dart';
 
 class TextInputBox extends StatelessWidget {
   const TextInputBox({
-    Key key,
-    @required this.icon,
-    @required this.hintText,
+    Key? key,
+    required this.icon,
+    required this.hintText,
     this.obscureText = false,
   }) : super(key: key);
 

section_4/login_example_sequence_animation/lib/widgets/header.dart

@@ -4,10 +4,10 @@ import '../styles/colors.dart';
 
 class Header extends StatelessWidget {
   const Header({
-    Key key,
-    @required double scale,
-    @required double height,
-    @required bool isLogin,
+    Key? key,
+    required double scale,
+    required double height,
+    required bool isLogin,
   })  : _scale = scale,
         _height = height,
         _isLogin = isLogin,
@@ -36,7 +36,7 @@ class Header extends StatelessWidget {
             headerText,
             overflow: TextOverflow.fade,
             maxLines: 1,
-            style: Theme.of(context).textTheme.headline5.copyWith(
+            style: Theme.of(context).textTheme.headline5!.copyWith(
                   color: Colors.white,
                 ),
           ),

section_4/login_example_sequence_animation/pubspec.yaml

@@ -14,7 +14,7 @@ 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: