null safety support and test on different platforms

tip_003_popup_card/lib/add_todo_button.dart

@@ -13,7 +13,7 @@ import 'hero_dialog_route.dart';
 /// {@endtemplate}
 class AddTodoButton extends StatelessWidget {
   /// {@macro add_todo_button}
-  const AddTodoButton({Key key}) : super(key: key);
+  const AddTodoButton({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {
@@ -57,7 +57,7 @@ const String _heroAddTodo = 'add-todo-hero';
 /// {@endtemplate}
 class _AddTodoPopupCard extends StatelessWidget {
   /// {@macro add_todo_popup_card}
-  const _AddTodoPopupCard({Key key}) : super(key: key);
+  const _AddTodoPopupCard({Key? key}) : super(key: key);
 
   @override
   Widget build(BuildContext context) {

tip_003_popup_card/lib/custom_rect_tween.dart

@@ -10,18 +10,18 @@ import 'package:flutter/widgets.dart';
 class CustomRectTween extends RectTween {
   /// {@macro custom_rect_tween}
   CustomRectTween({
-    @required Rect begin,
-    @required Rect end,
+    required Rect? begin,
+    required Rect? end,
   }) : super(begin: begin, end: end);
 
   @override
   Rect lerp(double t) {
     final elasticCurveValue = Curves.easeOut.transform(t);
     return Rect.fromLTRB(
-      lerpDouble(begin.left, end.left, elasticCurveValue),
-      lerpDouble(begin.top, end.top, elasticCurveValue),
-      lerpDouble(begin.right, end.right, elasticCurveValue),
-      lerpDouble(begin.bottom, end.bottom, elasticCurveValue),
+      lerpDouble(begin!.left, end!.left, elasticCurveValue)!,
+      lerpDouble(begin!.top, end!.top, elasticCurveValue)!,
+      lerpDouble(begin!.right, end!.right, elasticCurveValue)!,
+      lerpDouble(begin!.bottom, end!.bottom, elasticCurveValue)!,
     );
   }
 }

tip_003_popup_card/lib/hero_dialog_route.dart

@@ -10,8 +10,8 @@ import 'package:flutter/material.dart';
 class HeroDialogRoute<T> extends PageRoute<T> {
   /// {@macro hero_dialog_route}
   HeroDialogRoute({
-    @required WidgetBuilder builder,
-    RouteSettings settings,
+    required WidgetBuilder builder,
+    RouteSettings? settings,
     bool fullscreenDialog = false,
   })  : _builder = builder,
         super(settings: settings, fullscreenDialog: fullscreenDialog);

tip_003_popup_card/lib/main.dart

@@ -33,7 +33,7 @@ class MyApp extends StatelessWidget {
 class Home extends StatelessWidget {
   /// {@macro home}
   const Home({
-    Key key,
+    Key? key,
   }) : super(key: key);
 
   @override
@@ -74,8 +74,8 @@ class Home extends StatelessWidget {
 /// {@endtemplate}
 class _TodoListContent extends StatelessWidget {
   const _TodoListContent({
-    Key key,
-    @required this.todos,
+    Key? key,
+    required this.todos,
   }) : super(key: key);
 
   final List<Todo> todos;
@@ -101,8 +101,8 @@ class _TodoListContent extends StatelessWidget {
 class _TodoCard extends StatelessWidget {
   /// {@macro todo_card}
   const _TodoCard({
-    Key key,
-    @required this.todo,
+    Key? key,
+    required this.todo,
   }) : super(key: key);
 
   final Todo todo;
@@ -157,8 +157,8 @@ class _TodoCard extends StatelessWidget {
 class _TodoTitle extends StatelessWidget {
   /// {@macro todo_title}
   const _TodoTitle({
-    Key key,
-    @required this.title,
+    Key? key,
+    required this.title,
   }) : super(key: key);
 
   final String title;
@@ -178,13 +178,13 @@ class _TodoTitle extends StatelessWidget {
 /// Activated from [_TodoCard].
 /// {@endtemplate}
 class _TodoPopupCard extends StatelessWidget {
-  const _TodoPopupCard({Key key, this.todo}) : super(key: key);
-  final Todo todo;
+  const _TodoPopupCard({Key? key, this.todo}) : super(key: key);
+  final Todo? todo;
 
   @override
   Widget build(BuildContext context) {
     return Hero(
-      tag: todo.id,
+      tag: todo!.id,
       createRectTween: (begin, end) {
         return CustomRectTween(begin: begin, end: end);
       },
@@ -200,13 +200,13 @@ class _TodoPopupCard extends StatelessWidget {
                 child: Column(
                   mainAxisSize: MainAxisSize.min,
                   children: [
-                    _TodoTitle(title: todo.description),
+                    _TodoTitle(title: todo!.description),
                     const SizedBox(
                       height: 8,
                     ),
-                    if (todo.items != null) ...[
+                    if (todo!.items != null) ...[
                       const Divider(),
-                      _TodoItemsBox(items: todo.items),
+                      _TodoItemsBox(items: todo!.items),
                     ],
                     Container(
                       margin: const EdgeInsets.all(8),
@@ -242,17 +242,17 @@ class _TodoPopupCard extends StatelessWidget {
 class _TodoItemsBox extends StatelessWidget {
   /// {@macro todo_items_box}
   const _TodoItemsBox({
-    Key key,
-    @required this.items,
+    Key? key,
+    required this.items,
   }) : super(key: key);
 
-  final List<Item> items;
+  final List<Item>? items;
 
   @override
   Widget build(BuildContext context) {
     return Column(
       children: [
-        for (final item in items) _TodoItemTile(item: item),
+        for (final item in items!) _TodoItemTile(item: item),
       ],
     );
   }
@@ -264,8 +264,8 @@ class _TodoItemsBox extends StatelessWidget {
 class _TodoItemTile extends StatefulWidget {
   /// {@macro todo_item_template}
   const _TodoItemTile({
-    Key key,
-    @required this.item,
+    Key? key,
+    required this.item,
   }) : super(key: key);
 
   final Item item;
@@ -275,7 +275,7 @@ class _TodoItemTile extends StatefulWidget {
 }
 
 class _TodoItemTileState extends State<_TodoItemTile> {
-  void _onChanged(bool val) {
+  void _onChanged(bool? val) {
     setState(() {
       widget.item.completed = val;
     });

tip_003_popup_card/lib/models.dart

@@ -7,8 +7,8 @@ import 'package:meta/meta.dart';
 class Todo {
   /// {@macro todo}
   const Todo({
-    @required this.id,
-    @required this.description,
+    required this.id,
+    required this.description,
     this.items,
   });
 
@@ -19,7 +19,7 @@ class Todo {
   final String description;
 
   /// A list of [Item]s for sub-todos.
-  final List<Item> items;
+  final List<Item>? items;
 }
 
 /// {@template item}
@@ -28,7 +28,7 @@ class Todo {
 class Item {
   /// {@macro item}
   Item({
-    @required this.id,
+    required this.id,
     this.description = '',
     this.completed = false,
   });
@@ -40,5 +40,5 @@ class Item {
   final String description;
 
   /// Indicates if this item has been completed or not.
-  bool completed;
+  bool? completed;
 }

tip_003_popup_card/pubspec.lock

@@ -7,42 +7,42 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.5.0-nullsafety.1"
+    version: "2.5.0"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety.1"
+    version: "2.1.0"
   characters:
     dependency: transitive
     description:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety.3"
+    version: "1.1.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0-nullsafety.1"
+    version: "1.2.0"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety.1"
+    version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.15.0-nullsafety.3"
+    version: "1.15.0"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -56,7 +56,7 @@ packages:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0-nullsafety.1"
+    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: "0.12.10-nullsafety.1"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety.3"
+    version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0-nullsafety.1"
+    version: "1.8.0"
   pedantic:
     dependency: transitive
     description:
@@ -113,56 +113,56 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0-nullsafety.2"
+    version: "1.8.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.10.0-nullsafety.1"
+    version: "1.10.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety.1"
+    version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety.1"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0-nullsafety.1"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.19-nullsafety.2"
+    version: "0.2.19"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety.3"
+    version: "1.3.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety.3"
+    version: "2.1.0"
   very_good_analysis:
     dependency: "direct dev"
     description:
@@ -171,5 +171,5 @@ packages:
     source: hosted
     version: "1.0.4"
 sdks:
-  dart: ">=2.10.0-110 <2.11.0"
+  dart: ">=2.12.0 <3.0.0"
   flutter: ">=1.17.0"

tip_003_popup_card/pubspec.yaml

@@ -18,7 +18,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter: