[Gallery] Crane focus (#254)

* Add debugLabel to HighlightFocus

* Remove decrated property

* Add focus to DestinationCards

* Add index property to Forms

* Move BackLayer stuff to its own file

* Add focus

* Revert deprecated change

* Address feedback

gallery/gallery/lib/layout/highlight_focus.dart

@@ -15,6 +15,7 @@ class HighlightFocus extends StatefulWidget {
     this.highlightColor,
     this.borderColor,
     this.hasFocus = true,
+    this.debugLabel,
   });
 
   /// [onPressed] is called when you press space, enter, or numpad-enter
@@ -37,6 +38,8 @@ class HighlightFocus extends StatefulWidget {
   /// Set to false if you want the child to skip focus.
   final bool hasFocus;
 
+  final String debugLabel;
+
   @override
   _HighlightFocusState createState() => _HighlightFocusState();
 }
@@ -67,6 +70,7 @@ class _HighlightFocusState extends State<HighlightFocus> {
 
     return Focus(
       canRequestFocus: widget.hasFocus,
+      debugLabel: widget.debugLabel,
       onFocusChange: (newValue) {
         setState(() {
           isFocused = newValue;

gallery/gallery/lib/studies/crane/app.dart

@@ -41,10 +41,10 @@ class _CraneAppState extends State<CraneApp> {
       home: ApplyTextOptions(
         child: Backdrop(
           frontLayer: Container(),
-          backLayer: [
-            FlyForm(),
-            SleepForm(),
-            EatForm(),
+          backLayerItems: [
+            FlyForm(index: 0),
+            SleepForm(index: 1),
+            EatForm(index: 2),
           ],
           frontTitle: Text('CRANE'),
           backTitle: Text('MENU'),

gallery/gallery/lib/studies/crane/backdrop.dart

@@ -13,6 +13,7 @@ import 'package:gallery/data/gallery_options.dart';
 import 'package:gallery/l10n/gallery_localizations.dart';
 import 'package:gallery/layout/adaptive.dart';
 import 'package:gallery/studies/crane/border_tab_indicator.dart';
+import 'package:gallery/studies/crane/backlayer.dart';
 import 'package:gallery/studies/crane/colors.dart';
 import 'package:gallery/studies/crane/item_cards.dart';
 
@@ -32,26 +33,29 @@ class _FrontLayer extends StatelessWidget {
   Widget build(BuildContext context) {
     final isDesktop = isDisplayDesktop(context);
 
-    return PhysicalShape(
-      elevation: 16,
-      color: cranePrimaryWhite,
-      clipper: ShapeBorderClipper(
-        shape: RoundedRectangleBorder(
-          borderRadius: BorderRadius.only(
-            topLeft: Radius.circular(frontLayerBorderRadius),
-            topRight: Radius.circular(frontLayerBorderRadius),
+    return DefaultFocusTraversal(
+      policy: ReadingOrderTraversalPolicy(),
+      child: PhysicalShape(
+        elevation: 16,
+        color: cranePrimaryWhite,
+        clipper: ShapeBorderClipper(
+          shape: RoundedRectangleBorder(
+            borderRadius: BorderRadius.only(
+              topLeft: Radius.circular(frontLayerBorderRadius),
+              topRight: Radius.circular(frontLayerBorderRadius),
+            ),
           ),
         ),
-      ),
-      child: ListView(
-        padding: isDesktop
-            ? EdgeInsets.symmetric(horizontal: 120, vertical: 22)
-            : EdgeInsets.all(20),
-        children: [
-          Text(title, style: Theme.of(context).textTheme.subtitle),
-          SizedBox(height: 20),
-          ItemCards(index: index),
-        ],
+        child: ListView(
+          padding: isDesktop
+              ? EdgeInsets.symmetric(horizontal: 120, vertical: 22)
+              : EdgeInsets.all(20),
+          children: [
+            Text(title, style: Theme.of(context).textTheme.subtitle),
+            SizedBox(height: 20),
+            ItemCards(index: index),
+          ],
+        ),
       ),
     );
   }
@@ -65,17 +69,17 @@ class _FrontLayer extends StatelessWidget {
 /// front or back layer is showing.
 class Backdrop extends StatefulWidget {
   final Widget frontLayer;
-  final List<Widget> backLayer;
+  final List<BackLayerItem> backLayerItems;
   final Widget frontTitle;
   final Widget backTitle;
 
   const Backdrop({
     @required this.frontLayer,
-    @required this.backLayer,
+    @required this.backLayerItems,
     @required this.frontTitle,
     @required this.backTitle,
   })  : assert(frontLayer != null),
-        assert(backLayer != null),
+        assert(backLayerItems != null),
         assert(frontTitle != null),
         assert(backTitle != null);
 
@@ -125,61 +129,68 @@ class _BackdropState extends State<Backdrop> with TickerProviderStateMixin {
       color: cranePurple800,
       child: Padding(
         padding: EdgeInsets.only(top: 12),
-        child: Scaffold(
-          backgroundColor: cranePurple800,
-          appBar: AppBar(
-            brightness: Brightness.dark,
-            elevation: 0,
-            titleSpacing: 0,
-            flexibleSpace: CraneAppBar(
-              tabController: _tabController,
-              tabHandler: _handleTabs,
-            ),
-          ),
-          body: Stack(
-            children: [
-              BackLayer(
+        child: DefaultFocusTraversal(
+          policy: ReadingOrderTraversalPolicy(),
+          child: Scaffold(
+            backgroundColor: cranePurple800,
+            appBar: AppBar(
+              brightness: Brightness.dark,
+              elevation: 0,
+              titleSpacing: 0,
+              flexibleSpace: CraneAppBar(
                 tabController: _tabController,
-                backLayers: widget.backLayer,
+                tabHandler: _handleTabs,
               ),
-              Container(
-                margin: EdgeInsets.only(
-                  top: isDesktop
-                      ? 60 + 20 * textScaleFactor / 2
-                      : 175 + 140 * textScaleFactor / 2,
-                ),
-                child: TabBarView(
-                  physics: isDesktop
-                      ? NeverScrollableScrollPhysics()
-                      : null, // use default TabBarView physics
-                  controller: _tabController,
-                  children: [
-                    SlideTransition(
-                      position: _flyLayerOffset,
-                      child: _FrontLayer(
-                        title: GalleryLocalizations.of(context).craneFlySubhead,
-                        index: 0,
-                      ),
-                    ),
-                    SlideTransition(
-                      position: _sleepLayerOffset,
-                      child: _FrontLayer(
-                        title:
-                            GalleryLocalizations.of(context).craneSleepSubhead,
-                        index: 1,
-                      ),
+            ),
+            body: FocusScope(
+              child: Stack(
+                children: [
+                  BackLayer(
+                    tabController: _tabController,
+                    backLayerItems: widget.backLayerItems,
+                  ),
+                  Container(
+                    margin: EdgeInsets.only(
+                      top: isDesktop
+                          ? 60 + 20 * textScaleFactor / 2
+                          : 175 + 140 * textScaleFactor / 2,
                     ),
-                    SlideTransition(
-                      position: _eatLayerOffset,
-                      child: _FrontLayer(
-                        title: GalleryLocalizations.of(context).craneEatSubhead,
-                        index: 2,
-                      ),
+                    child: TabBarView(
+                      physics: isDesktop
+                          ? NeverScrollableScrollPhysics()
+                          : null, // use default TabBarView physics
+                      controller: _tabController,
+                      children: [
+                        SlideTransition(
+                          position: _flyLayerOffset,
+                          child: _FrontLayer(
+                            title: GalleryLocalizations.of(context)
+                                .craneFlySubhead,
+                            index: 0,
+                          ),
+                        ),
+                        SlideTransition(
+                          position: _sleepLayerOffset,
+                          child: _FrontLayer(
+                            title: GalleryLocalizations.of(context)
+                                .craneSleepSubhead,
+                            index: 1,
+                          ),
+                        ),
+                        SlideTransition(
+                          position: _eatLayerOffset,
+                          child: _FrontLayer(
+                            title: GalleryLocalizations.of(context)
+                                .craneEatSubhead,
+                            index: 2,
+                          ),
+                        ),
+                      ],
                     ),
-                  ],
-                ),
+                  ),
+                ],
               ),
-            ],
+            ),
           ),
         ),
       ),
@@ -187,33 +198,6 @@ class _BackdropState extends State<Backdrop> with TickerProviderStateMixin {
   }
 }
 
-class BackLayer extends StatefulWidget {
-  final List<Widget> backLayers;
-  final TabController tabController;
-
-  const BackLayer({Key key, this.backLayers, this.tabController})
-      : super(key: key);
-
-  @override
-  _BackLayerState createState() => _BackLayerState();
-}
-
-class _BackLayerState extends State<BackLayer> {
-  @override
-  void initState() {
-    super.initState();
-    widget.tabController.addListener(() => setState(() {}));
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return IndexedStack(
-      index: widget.tabController.index,
-      children: widget.backLayers,
-    );
-  }
-}
-
 class CraneAppBar extends StatefulWidget {
   final Function(int) tabHandler;
   final TabController tabController;

gallery/gallery/lib/studies/crane/backlayer.dart

@@ -0,0 +1,49 @@
+// Copyright 2019 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+abstract class BackLayerItem extends StatefulWidget {
+  final int index;
+
+  BackLayerItem({Key key, this.index}) : super(key: key);
+}
+
+class BackLayer extends StatefulWidget {
+  final List<BackLayerItem> backLayerItems;
+  final TabController tabController;
+
+  const BackLayer({Key key, this.backLayerItems, this.tabController})
+      : super(key: key);
+
+  @override
+  _BackLayerState createState() => _BackLayerState();
+}
+
+class _BackLayerState extends State<BackLayer> {
+  @override
+  void initState() {
+    super.initState();
+    widget.tabController.addListener(() => setState(() {}));
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final tabIndex = widget.tabController.index;
+    return DefaultFocusTraversal(
+      policy: WidgetOrderFocusTraversalPolicy(),
+      child: IndexedStack(
+        index: tabIndex,
+        children: [
+          for (BackLayerItem backLayerItem in widget.backLayerItems)
+            Focus(
+              canRequestFocus: backLayerItem.index == tabIndex,
+              debugLabel: 'backLayerItem: $backLayerItem',
+              child: backLayerItem,
+            )
+        ],
+      ),
+    );
+  }
+}

gallery/gallery/lib/studies/crane/eat_form.dart

@@ -5,9 +5,12 @@
 import 'package:flutter/material.dart';
 
 import 'package:gallery/l10n/gallery_localizations.dart';
+import 'package:gallery/studies/crane/backlayer.dart';
 import 'package:gallery/studies/crane/header_form.dart';
 
-class EatForm extends StatefulWidget {
+class EatForm extends BackLayerItem {
+  EatForm({int index}) : super(index: index);
+
   @override
   _EatFormState createState() => _EatFormState();
 }

gallery/gallery/lib/studies/crane/fly_form.dart

@@ -5,9 +5,12 @@
 import 'package:flutter/material.dart';
 
 import 'package:gallery/l10n/gallery_localizations.dart';
+import 'package:gallery/studies/crane/backlayer.dart';
 import 'package:gallery/studies/crane/header_form.dart';
 
-class FlyForm extends StatefulWidget {
+class FlyForm extends BackLayerItem {
+  FlyForm({int index}) : super(index: index);
+
   @override
   _FlyFormState createState() => _FlyFormState();
 }

gallery/gallery/lib/studies/crane/item_cards.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:gallery/layout/adaptive.dart';
+import 'package:gallery/layout/highlight_focus.dart';
 import 'package:gallery/studies/crane/model/data.dart';
 import 'package:gallery/studies/crane/model/destination.dart';
 
@@ -33,8 +34,13 @@ class _ItemCardsState extends State<ItemCards> {
 
     return destinations
         .map(
-          (d) => RepaintBoundary(
-            child: _DestinationCard(destination: d),
+          (d) => HighlightFocus(
+            debugLabel: 'DestinationCard: ${d.destination}',
+            highlightColor: Colors.red.withOpacity(0.5),
+            onPressed: () {},
+            child: RepaintBoundary(
+              child: _DestinationCard(destination: d),
+            ),
           ),
         )
         .toList();

gallery/gallery/lib/studies/crane/sleep_form.dart

@@ -5,9 +5,12 @@
 import 'package:flutter/material.dart';
 import 'package:gallery/l10n/gallery_localizations.dart';
 
+import 'package:gallery/studies/crane/backlayer.dart';
 import 'package:gallery/studies/crane/header_form.dart';
 
-class SleepForm extends StatefulWidget {
+class SleepForm extends BackLayerItem {
+  SleepForm({int index}) : super(index: index);
+
   @override
   _SleepFormState createState() => _SleepFormState();
 }