[Gallery] Fix directory structure (#312)

gallery/lib/demos/material/bottom_navigation_demo.dart

@@ -0,0 +1,212 @@
+// 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';
+
+import 'package:gallery/l10n/gallery_localizations.dart';
+
+// BEGIN bottomNavigationDemo
+
+enum BottomNavigationDemoType {
+  withLabels,
+  withoutLabels,
+}
+
+class BottomNavigationDemo extends StatefulWidget {
+  BottomNavigationDemo({Key key, @required this.type}) : super(key: key);
+
+  final BottomNavigationDemoType type;
+
+  @override
+  _BottomNavigationDemoState createState() => _BottomNavigationDemoState();
+}
+
+class _BottomNavigationDemoState extends State<BottomNavigationDemo>
+    with TickerProviderStateMixin {
+  int _currentIndex = 0;
+  List<_NavigationIconView> _navigationViews;
+
+  String _title(BuildContext context) {
+    switch (widget.type) {
+      case BottomNavigationDemoType.withLabels:
+        return GalleryLocalizations.of(context)
+            .demoBottomNavigationPersistentLabels;
+      case BottomNavigationDemoType.withoutLabels:
+        return GalleryLocalizations.of(context)
+            .demoBottomNavigationSelectedLabel;
+    }
+    return '';
+  }
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    if (_navigationViews == null) {
+      _navigationViews = <_NavigationIconView>[
+        _NavigationIconView(
+          icon: const Icon(Icons.add_comment),
+          title: GalleryLocalizations.of(context).bottomNavigationCommentsTab,
+          vsync: this,
+        ),
+        _NavigationIconView(
+          icon: const Icon(Icons.calendar_today),
+          title: GalleryLocalizations.of(context).bottomNavigationCalendarTab,
+          vsync: this,
+        ),
+        _NavigationIconView(
+          icon: const Icon(Icons.account_circle),
+          title: GalleryLocalizations.of(context).bottomNavigationAccountTab,
+          vsync: this,
+        ),
+        _NavigationIconView(
+          icon: const Icon(Icons.alarm_on),
+          title: GalleryLocalizations.of(context).bottomNavigationAlarmTab,
+          vsync: this,
+        ),
+        _NavigationIconView(
+          icon: const Icon(Icons.camera_enhance),
+          title: GalleryLocalizations.of(context).bottomNavigationCameraTab,
+          vsync: this,
+        ),
+      ];
+
+      _navigationViews[_currentIndex].controller.value = 1;
+    }
+  }
+
+  @override
+  void dispose() {
+    for (_NavigationIconView view in _navigationViews) {
+      view.controller.dispose();
+    }
+    super.dispose();
+  }
+
+  Widget _buildTransitionsStack() {
+    final List<FadeTransition> transitions = <FadeTransition>[];
+
+    for (_NavigationIconView view in _navigationViews) {
+      transitions.add(view.transition(context));
+    }
+
+    // We want to have the newly animating (fading in) views on top.
+    transitions.sort((a, b) {
+      final aAnimation = a.opacity;
+      final bAnimation = b.opacity;
+      final aValue = aAnimation.value;
+      final bValue = bAnimation.value;
+      return aValue.compareTo(bValue);
+    });
+
+    return Stack(children: transitions);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final textTheme = Theme.of(context).textTheme;
+
+    var bottomNavigationBarItems = _navigationViews
+        .map<BottomNavigationBarItem>((navigationView) => navigationView.item)
+        .toList();
+    if (widget.type == BottomNavigationDemoType.withLabels) {
+      bottomNavigationBarItems =
+          bottomNavigationBarItems.sublist(0, _navigationViews.length - 2);
+      _currentIndex =
+          _currentIndex.clamp(0, bottomNavigationBarItems.length - 1).toInt();
+    }
+
+    return Scaffold(
+      appBar: AppBar(
+        automaticallyImplyLeading: false,
+        title: Text(_title(context)),
+      ),
+      body: Center(
+        child: _buildTransitionsStack(),
+      ),
+      bottomNavigationBar: BottomNavigationBar(
+        showUnselectedLabels:
+            widget.type == BottomNavigationDemoType.withLabels,
+        items: bottomNavigationBarItems,
+        currentIndex: _currentIndex,
+        type: BottomNavigationBarType.fixed,
+        selectedFontSize: textTheme.caption.fontSize,
+        unselectedFontSize: textTheme.caption.fontSize,
+        onTap: (index) {
+          setState(() {
+            _navigationViews[_currentIndex].controller.reverse();
+            _currentIndex = index;
+            _navigationViews[_currentIndex].controller.forward();
+          });
+        },
+        selectedItemColor: colorScheme.onPrimary,
+        unselectedItemColor: colorScheme.onPrimary.withOpacity(0.38),
+        backgroundColor: colorScheme.primary,
+      ),
+    );
+  }
+}
+
+class _NavigationIconView {
+  _NavigationIconView({
+    this.title,
+    this.icon,
+    TickerProvider vsync,
+  })  : item = BottomNavigationBarItem(
+          icon: icon,
+          title: Text(title),
+        ),
+        controller = AnimationController(
+          duration: kThemeAnimationDuration,
+          vsync: vsync,
+        ) {
+    _animation = controller.drive(CurveTween(
+      curve: const Interval(0.5, 1.0, curve: Curves.fastOutSlowIn),
+    ));
+  }
+
+  final String title;
+  final Widget icon;
+  final BottomNavigationBarItem item;
+  final AnimationController controller;
+  Animation<double> _animation;
+
+  FadeTransition transition(BuildContext context) {
+    return FadeTransition(
+      opacity: _animation,
+      child: Stack(
+        children: [
+          ExcludeSemantics(
+            child: Center(
+              child: Padding(
+                padding: const EdgeInsets.all(16),
+                child: ClipRRect(
+                  borderRadius: BorderRadius.circular(8),
+                  child: Image.asset(
+                    'assets/demos/bottom_navigation_background.png',
+                  ),
+                ),
+              ),
+            ),
+          ),
+          Center(
+            child: IconTheme(
+              data: IconThemeData(
+                color: Colors.white,
+                size: 80,
+              ),
+              child: Semantics(
+                label: GalleryLocalizations.of(context)
+                    .bottomNavigationContentPlaceholder(title),
+                child: icon,
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+// END