D1APP-93 floating back button added to pageview

lib/widgets/didvan/page_view.dart

@@ -1,9 +1,14 @@
 import 'package:carousel_slider/carousel_slider.dart';
+import 'package:didvan/config/design_config.dart';
+import 'package:didvan/config/theme_data.dart';
+import 'package:didvan/constants/app_icons.dart';
 import 'package:didvan/pages/home/widgets/multitype_overview.dart';
 import 'package:didvan/utils/date_time.dart';
+import 'package:didvan/widgets/animated_visibility.dart';
 import 'package:didvan/widgets/didvan/card.dart';
 import 'package:didvan/widgets/didvan/divider.dart';
 import 'package:didvan/widgets/didvan/text.dart';
+import 'package:didvan/widgets/ink_wrapper.dart';
 import 'package:didvan/widgets/item_title.dart';
 import 'package:didvan/widgets/skeleton_image.dart';
 import 'package:didvan/pages/home/widgets/tag_item.dart';
@@ -36,7 +41,9 @@ class _DidvanPageViewState extends State<DidvanPageView> {
   @override
   Widget build(BuildContext context) {
     final double deviceTopPadding = MediaQuery.of(context).padding.top;
-    return Directionality(
+    return Stack(
+      children: [
+        Directionality(
           textDirection: TextDirection.ltr,
           child: CarouselSlider.builder(
             itemCount: widget.items.length,
@@ -52,8 +59,9 @@ class _DidvanPageViewState extends State<DidvanPageView> {
               child: SizedBox(
                 height: MediaQuery.of(context).size.height,
                 child: SingleChildScrollView(
-              controller:
+                  controller: index == widget.currentIndex
-                  index == widget.currentIndex ? widget.scrollController : null,
+                      ? widget.scrollController
+                      : null,
                   physics: const BouncingScrollPhysics(),
                   padding: EdgeInsets.only(
                     left: 4,
@@ -79,7 +87,8 @@ class _DidvanPageViewState extends State<DidvanPageView> {
                             ),
                             const SizedBox(height: 20),
                             Padding(
-                          padding: const EdgeInsets.symmetric(horizontal: 16),
+                              padding:
+                                  const EdgeInsets.symmetric(horizontal: 16),
                               child: DidvanText(
                                 item.title,
                                 style: Theme.of(context).textTheme.subtitle1,
@@ -87,7 +96,8 @@ class _DidvanPageViewState extends State<DidvanPageView> {
                             ),
                             const SizedBox(height: 8),
                             Padding(
-                          padding: const EdgeInsets.symmetric(horizontal: 16),
+                              padding:
+                                  const EdgeInsets.symmetric(horizontal: 16),
                               child: _subtitle(item),
                             ),
                             for (var i = 0; i < item.contents.length; i++)
@@ -98,9 +108,11 @@ class _DidvanPageViewState extends State<DidvanPageView> {
                                 ),
                                 child: _contentBuilder(item, i),
                               ),
-                        if (item.tags.isNotEmpty) const SizedBox(height: 20),
+                            if (item.tags.isNotEmpty)
+                              const SizedBox(height: 20),
                             Padding(
-                          padding: const EdgeInsets.symmetric(horizontal: 16),
+                              padding:
+                                  const EdgeInsets.symmetric(horizontal: 16),
                               child: Wrap(
                                 spacing: 8,
                                 runSpacing: 8,
@@ -132,7 +144,9 @@ class _DidvanPageViewState extends State<DidvanPageView> {
                                   ),
                                   child: MultitypeOverview.placeholder,
                                 ),
-                        for (var i = 0; i < item.relatedContents.length; i++)
+                            for (var i = 0;
+                                i < item.relatedContents.length;
+                                i++)
                               Padding(
                                 padding: const EdgeInsets.only(
                                   bottom: 8,
@@ -154,6 +168,13 @@ class _DidvanPageViewState extends State<DidvanPageView> {
               ),
             ),
           ),
+        ),
+        Positioned(
+          child: _BackButton(scrollController: widget.scrollController),
+          right: 24,
+          top: 24 + deviceTopPadding,
+        ),
+      ],
     );
   }
 
@@ -219,3 +240,66 @@ class _DidvanPageViewState extends State<DidvanPageView> {
     }
   }
 }
+
+class _BackButton extends StatefulWidget {
+  final ScrollController scrollController;
+  const _BackButton({Key? key, required this.scrollController})
+      : super(key: key);
+
+  @override
+  __BackButtonState createState() => __BackButtonState();
+}
+
+class __BackButtonState extends State<_BackButton> {
+  bool _isVisible = false;
+
+  @override
+  void didUpdateWidget(covariant _BackButton oldWidget) {
+    _isVisible = false;
+    _handleScroll();
+    super.didUpdateWidget(oldWidget);
+  }
+
+  @override
+  void initState() {
+    _handleScroll();
+    super.initState();
+  }
+
+  void _handleScroll() {
+    widget.scrollController.addListener(() {
+      final position = widget.scrollController.position.pixels;
+      final size = MediaQuery.of(context).size.height * 0.3;
+      if (position > size && _isVisible == false) {
+        setState(() {
+          _isVisible = true;
+        });
+      }
+      if (position < size && _isVisible == true) {
+        setState(() {
+          _isVisible = false;
+        });
+      }
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedVisibility(
+      duration: DesignConfig.lowAnimationDuration,
+      isVisible: _isVisible,
+      child: InkWrapper(
+        borderRadius: DesignConfig.lowBorderRadius,
+        onPressed: Navigator.of(context).pop,
+        child: Container(
+          decoration: BoxDecoration(
+            color: Theme.of(context).colorScheme.splash,
+            border: Border.all(color: Theme.of(context).colorScheme.border),
+            borderRadius: DesignConfig.lowBorderRadius,
+          ),
+          child: const Icon(DidvanIcons.back_regular, size: 32),
+        ),
+      ),
+    );
+  }
+}