Updated example and v2 of lazy_load_scrollview

analysis_options.yaml

@@ -0,0 +1,21 @@
+include: package:flutter_lints/flutter.yaml
+
+analyzer:
+  strong-mode:
+    implicit-casts: false
+    implicit-dynamic: false
+
+linter:
+  rules:
+    # - public_member_api_docs
+    - require_trailing_commas
+    - parameter_assignments
+    - only_throw_errors
+    - always_use_package_imports
+    - avoid_dynamic_calls
+    - prefer_void_to_null
+    - always_declare_return_types
+    - avoid_classes_with_only_static_members
+    - unnecessary_lambdas
+    - unnecessary_const
+    - avoid_void_async

example/ios/Flutter/AppFrameworkInfo.plist

@@ -21,6 +21,6 @@
   <key>CFBundleVersion</key>
   <string>1.0</string>
   <key>MinimumOSVersion</key>
-  <string>8.0</string>
+  <string>9.0</string>
 </dict>
 </plist>

example/lib/main.dart

@@ -1,74 +1,84 @@
 import 'package:flutter/material.dart';
 import 'package:lazy_load_scrollview/lazy_load_scrollview.dart';
 
-void main() => runApp(new MyApp());
+void main() => runApp(const MyApp());
 
 class MyApp extends StatelessWidget {
-  // This widget is the root of your application.
+  const MyApp({Key? key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
-    return new MaterialApp(
+    return const MaterialApp(
       title: 'Lazy Load Demo',
-      home: new MyHomePage(title: 'Lazy Load Demo'),
+      home: MyHomePage(title: 'Lazy Load Demo'),
     );
   }
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({Key? key, required this.title}) : super(key: key);
+  const MyHomePage({Key? key, required this.title}) : super(key: key);
 
   final String title;
 
   @override
-  _MyHomePageState createState() => new _MyHomePageState();
+  _MyHomePageState createState() => _MyHomePageState();
 }
 
 class _MyHomePageState extends State<MyHomePage> {
+  final scrollController = ScrollController();
+
   List<int> verticalData = [];
   List<int> horizontalData = [];
 
   final int increment = 10;
 
-  bool isLoadingVertical = false;
-  bool isLoadingHorizontal = false;
-
   @override
   void initState() {
     _loadMoreVertical();
-    _loadMoreHorizontal();
+    _loadMoreHorizontalAfter();
     super.initState();
   }
 
-  Future _loadMoreVertical() async {
-    setState(() {
-      isLoadingVertical = true;
-    });
+  @override
+  void dispose() {
+    scrollController.dispose();
+    super.dispose();
+  }
 
+  Future _loadMoreVertical() async {
     // Add in an artificial delay
-    await new Future.delayed(const Duration(seconds: 2));
+    await Future<void>.delayed(const Duration(seconds: 2));
 
     verticalData.addAll(
-        List.generate(increment, (index) => verticalData.length + index));
-
-    setState(() {
-      isLoadingVertical = false;
-    });
+      List.generate(increment, (index) => verticalData.length + index),
+    );
+    setState(() {});
   }
 
-  Future _loadMoreHorizontal() async {
-    setState(() {
-      isLoadingHorizontal = true;
-    });
+  Future _loadMoreHorizontalBefore() async {
+    // Add in an artificial delay
+    await Future<void>.delayed(const Duration(seconds: 2));
+
+    final firstIndex = horizontalData.first - 1;
+
+    final previousToAdd = List.generate(
+      increment,
+      (index) => firstIndex - index,
+    );
+
+    horizontalData = [...previousToAdd.reversed, ...horizontalData];
+
+    setState(() {});
+  }
 
+  Future _loadMoreHorizontalAfter() async {
     // Add in an artificial delay
-    await new Future.delayed(const Duration(seconds: 2));
+    await Future<void>.delayed(const Duration(seconds: 2));
 
     horizontalData.addAll(
-        List.generate(increment, (index) => horizontalData.length + index));
-
-    setState(() {
-      isLoadingHorizontal = false;
-    });
+      List.generate(increment, (index) => horizontalData.length + index),
+    );
+    setState(() {});
   }
 
   @override
@@ -78,49 +88,87 @@ class _MyHomePageState extends State<MyHomePage> {
         title: Text(widget.title),
       ),
       body: LazyLoadScrollView(
-        isLoading: isLoadingVertical,
-        onEndOfPage: () => _loadMoreVertical(),
-        child: Scrollbar(
-          child: ListView(
-            children: [
-              Padding(
-                padding: const EdgeInsets.all(8.0),
-                child: Text(
-                  'Nested horizontal ListView',
-                  textAlign: TextAlign.center,
+        onLoadAfter: _loadMoreVertical,
+        controller: scrollController,
+        builder: (context, isLoadingAfter, _) {
+          // FIXME: I don't think this is true
+          // Scrollbar eats notifications ?? so we'll just use a scroll controller
+          return Scrollbar(
+            child: ListView(
+              controller: scrollController,
+              children: [
+                const Padding(
+                  padding: EdgeInsets.all(8.0),
+                  child: Text(
+                    'Nested horizontal ListView',
+                    textAlign: TextAlign.center,
+                  ),
                 ),
-              ),
-              Container(
-                  height: 180,
+                SizedBox(
+                  height: 300.0,
                   child: LazyLoadScrollView(
-                      isLoading: isLoadingHorizontal,
-                      scrollDirection: Axis.horizontal,
-                      onEndOfPage: () => _loadMoreHorizontal(),
-                      child: Scrollbar(
-                          child: ListView.builder(
-                              itemCount: horizontalData.length,
-                              scrollDirection: Axis.horizontal,
-                              itemBuilder: (context, position) {
-                                return DemoItem(position);
-                              })))),
-              Padding(
-                padding: const EdgeInsets.all(8.0),
-                child: Text(
-                  'Vertical ListView',
-                  textAlign: TextAlign.center,
+                    onLoadAfter: _loadMoreHorizontalAfter,
+                    onLoadBefore: _loadMoreHorizontalBefore,
+                    builder: (
+                      BuildContext context,
+                      bool isLoadingAfter,
+                      bool isLoadingBefore,
+                    ) {
+                      return CustomScrollView(
+                        scrollDirection: Axis.horizontal,
+                        slivers: [
+                          if (isLoadingBefore)
+                            const SliverToBoxAdapter(
+                              child: Center(child: CircularProgressIndicator()),
+                            ),
+                          SliverList(
+                            delegate: SliverChildBuilderDelegate(
+                              (context, index) {
+                                final position = horizontalData[index];
+
+                                return DemoItem(
+                                  position,
+                                  key: ValueKey(position),
+                                );
+                              },
+                              childCount: horizontalData.length,
+                              findChildIndexCallback: (key) {
+                                final valueKey = (key as ValueKey<int>).value;
+
+                                return horizontalData.indexOf(valueKey);
+                              },
+                            ),
+                          ),
+                          if (isLoadingAfter)
+                            const SliverToBoxAdapter(
+                              child: Center(child: CircularProgressIndicator()),
+                            ),
+                        ],
+                      );
+                    },
+                  ),
                 ),
-              ),
-              ListView.builder(
-                shrinkWrap: true,
-                physics: NeverScrollableScrollPhysics(),
-                itemCount: verticalData.length,
-                itemBuilder: (context, position) {
-                  return DemoItem(position);
-                },
-              ),
-            ],
-          ),
-        ),
+                const Padding(
+                  padding: EdgeInsets.all(8.0),
+                  child: Text(
+                    'Vertical ListView',
+                    textAlign: TextAlign.center,
+                  ),
+                ),
+                ListView.builder(
+                  shrinkWrap: true,
+                  physics: const NeverScrollableScrollPhysics(),
+                  itemCount: verticalData.length,
+                  itemBuilder: (context, position) {
+                    return DemoItem(position);
+                  },
+                ),
+                if (isLoadingAfter)
+                  const Center(child: CircularProgressIndicator()),
+              ],
+            ),
+          );
+        },
       ),
     );
   }
@@ -152,12 +200,13 @@ class DemoItem extends StatelessWidget {
                     height: 40.0,
                     width: 40.0,
                   ),
-                  SizedBox(width: 8.0),
-                  Text("Item $position"),
+                  const SizedBox(width: 8.0),
+                  Text("Item ${position.toString()}"),
                 ],
               ),
-              Text(
-                  "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque sed vulputate orci. Proin id scelerisque velit. Fusce at ligula ligula. Donec fringilla sapien odio, et faucibus tortor finibus sed. Aenean rutrum ipsum in sagittis auctor. Pellentesque mattis luctus consequat. Sed eget sapien ut nibh rhoncus cursus. Donec eget nisl aliquam, ornare sapien sit amet, lacinia quam."),
+              const Text(
+                "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque sed vulputate orci. Proin id scelerisque velit. Fusce at ligula ligula. Donec fringilla sapien odio, et faucibus tortor finibus sed. Aenean rutrum ipsum in sagittis auctor. Pellentesque mattis luctus consequat. Sed eget sapien ut nibh rhoncus cursus. Donec eget nisl aliquam, ornare sapien sit amet, lacinia quam.",
+              ),
             ],
           ),
         ),

example/pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.5.0"
+    version: "2.7.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -28,7 +28,7 @@ packages:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0"
+    version: "1.3.1"
   clock:
     dependency: transitive
     description:
@@ -55,6 +55,13 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_lints:
+    dependency: "direct dev"
+    description:
+      name: flutter_lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.4"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -66,7 +73,14 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "1.2.0"
+    version: "1.3.0"
+  lints:
+    dependency: transitive
+    description:
+      name: lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
   matcher:
     dependency: transitive
     description:
@@ -80,7 +94,7 @@ packages:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0"
+    version: "1.7.0"
   path:
     dependency: transitive
     description:
@@ -99,7 +113,7 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0"
+    version: "1.8.1"
   stack_trace:
     dependency: transitive
     description:
@@ -134,7 +148,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.19"
+    version: "0.4.1"
   typed_data:
     dependency: transitive
     description:

example/pubspec.yaml

@@ -14,5 +14,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  flutter_lints: ^1.0.0
+
 flutter:
   uses-material-design: true