load asset paged.

lib/src/provider/asset_provider.dart

+import 'dart:async';
+
+import 'package:photo_manager/photo_manager.dart';
+
+class AssetProvider {
+  Map<AssetPathEntity, AssetPaging> _dataMap = {};
+
+  AssetPathEntity _current;
+
+  AssetPathEntity get current => _current;
+
+  set current(AssetPathEntity current) {
+    _current = current;
+    if (_dataMap[current] == null) {
+      final paging = AssetPaging(current);
+      _dataMap[current] = paging;
+    }
+  }
+
+  List<AssetEntity> get data => _dataMap[current]?.data ?? [];
+
+  Future<void> loadMore() async {
+    final paging = getPaging();
+    if (paging != null) {
+      await paging.loadMore();
+    }
+  }
+
+  AssetPaging getPaging() => _dataMap[current];
+
+  bool get noMore => getPaging()?.noMore ?? false;
+
+  int get count => data?.length ?? 0;
+}
+
+class AssetPaging {
+  int page = 0;
+
+  List<AssetEntity> data = [];
+
+  final AssetPathEntity path;
+
+  final int pageCount;
+
+  bool noMore = false;
+
+  AssetPaging(this.path, {this.pageCount = 50});
+
+  Future<void> loadMore() async {
+    if (noMore == true) {
+      return;
+    }
+    var data = await path.getAssetListPaged(page, pageCount);
+    if (data.length == 0) {
+      noMore = true;
+    }
+    page++;
+    this.data.addAll(data);
+  }
+}

lib/src/provider/config_provider.dart

 import 'package:flutter/material.dart';
 import 'package:photo/src/entity/options.dart';
+import 'package:photo/src/provider/asset_provider.dart';
 import 'package:photo/src/provider/i18n_provider.dart';
 
-class ConfigProvider extends InheritedWidget {
+class PhotoPickerProvider extends InheritedWidget {
   final Options options;
   final I18nProvider provider;
+  final AssetProvider assetProvider = AssetProvider();
 
-  ConfigProvider({
+  PhotoPickerProvider({
     @required this.options,
     @required this.provider,
     @required Widget child,
     return true;
   }
 
-  static ConfigProvider of(BuildContext context) =>
-      context.inheritFromWidgetOfExactType(ConfigProvider);
+  static PhotoPickerProvider of(BuildContext context) =>
+      context.inheritFromWidgetOfExactType(PhotoPickerProvider);
+
+  static AssetProvider assetProviderOf(BuildContext context) =>
+      of(context).assetProvider;
 }

lib/src/ui/page/photo_main_page.dart

 import 'package:photo/src/engine/lru_cache.dart';
 import 'package:photo/src/engine/throttle.dart';
 import 'package:photo/src/entity/options.dart';
+import 'package:photo/src/provider/asset_provider.dart';
 import 'package:photo/src/provider/config_provider.dart';
 import 'package:photo/src/provider/gallery_list_provider.dart';
 import 'package:photo/src/provider/i18n_provider.dart';
     with SelectedProvider, GalleryListProvider {
   Options get options => widget.options;
 
-  I18nProvider get i18nProvider => ConfigProvider.of(context).provider;
+  I18nProvider get i18nProvider => PhotoPickerProvider.of(context).provider;
+  AssetProvider get assetProvider =>
+      PhotoPickerProvider.of(context).assetProvider;
 
-  List<AssetEntity> list = [];
+  List<AssetEntity> get list => assetProvider.data;
 
   Color get themeColor => options.themeColor;
 
     galleryPathList.clear();
     galleryPathList.addAll(pathList);
 
-    List<AssetEntity> imageList;
-
     if (pathList.isNotEmpty) {
-      imageList = await pathList[0].assetList;
-      _sortAssetList(imageList);
-      _currentPath = pathList[0];
+      assetProvider.current = pathList[0];
+      await assetProvider.loadMore();
     }
 
     for (var path in pathList) {
       }
     }
 
-    this.list.clear();
-    if (imageList != null) {
-      this.list.addAll(imageList);
-    }
     setState(() {
       _isInit = true;
     });
       return _buildLoading();
     }
 
+    final noMore = assetProvider.noMore;
+
+    final count = assetProvider.count + (noMore ? 0 : 1);
+
     return Container(
       color: options.dividerColor,
       child: GridView.builder(
           mainAxisSpacing: options.padding,
         ),
         itemBuilder: _buildItem,
-        itemCount: list.length,
+        itemCount: count,
       ),
     );
   }
 
   Widget _buildItem(BuildContext context, int index) {
+    final noMore = assetProvider.noMore;
+    if (!noMore && index == assetProvider.count) {
+      _loadMore();
+      return _buildLoading();
+    }
+
     var data = list[index];
     return RepaintBoundary(
       child: GestureDetector(
     );
   }
 
+  _loadMore() async {
+    await assetProvider.loadMore();
+    setState(() {});
+  }
+
   _buildMask(bool showMask) {
     return IgnorePointer(
       child: AnimatedContainer(
     setState(() {});
   }
 
-  void _onGalleryChange(AssetPathEntity assetPathEntity) {
-    _currentPath = assetPathEntity;
-
-    _currentPath.assetList.then((v) async {
-      _sortAssetList(v);
-      list.clear();
-      list.addAll(v);
-      scrollController.jumpTo(0.0);
-      await checkPickImageEntity();
+  void _onGalleryChange(AssetPathEntity assetPathEntity) async {
+    // _currentPath = assetPathEntity;
+
+    // _currentPath.assetList.then((v) async {
+    //   _sortAssetList(v);
+    //   list.clear();
+    //   list.addAll(v);
+    //   scrollController.jumpTo(0.0);
+    //   await checkPickImageEntity();
+    //   setState(() {});
+    // });
+    if (assetPathEntity != assetProvider.current) {
+      assetProvider.current = assetPathEntity;
+      await assetProvider.loadMore();
       setState(() {});
-    });
+    }
   }
 
   void _onItemClick(AssetEntity data, int index) {
     Navigator.of(context).push(
       MaterialPageRoute(
         builder: (ctx) {
-          return ConfigProvider(
-            provider: ConfigProvider.of(context).provider,
+          return PhotoPickerProvider(
+            provider: PhotoPickerProvider.of(context).provider,
             options: options,
             child: PhotoPreviewPage(
               selectedProvider: this,
               initIndex: index,
               changeProviderOnCheckChange: true,
               result: result,
+              isPreview: false,
+              assetProvider: assetProvider,
             ),
           );
         },
     isPushed = true;
     var v = await Navigator.of(context).push(
       MaterialPageRoute(
-        builder: (ctx) => ConfigProvider(
-          provider: ConfigProvider.of(context).provider,
+        builder: (ctx) => PhotoPickerProvider(
+          provider: PhotoPickerProvider.of(context).provider,
           options: options,
           child: PhotoPreviewPage(
             selectedProvider: this,
             list: List.of(selectedList),
             changeProviderOnCheckChange: false,
             result: result,
+            isPreview: true,
+            assetProvider: assetProvider,
           ),
         ),
       ),

lib/src/ui/page/photo_preview_page.dart

 
 import 'package:flutter/material.dart';
 import 'package:photo/src/entity/options.dart';
+import 'package:photo/src/provider/asset_provider.dart';
 import 'package:photo/src/provider/config_provider.dart';
 import 'package:photo/src/provider/selected_provider.dart';
 import 'package:photo/src/ui/page/photo_main_page.dart';
   /// 这个参数是控制在内部点击check后是否实时修改provider状态
   final bool changeProviderOnCheckChange;
 
+  /// 是否通过预览进来的
+  final bool isPreview;
+
   /// 这里封装了结果
   final PhotoPreviewResult result;
 
+  final AssetProvider assetProvider;
+
   const PhotoPreviewPage({
     Key key,
     @required this.selectedProvider,
     @required this.list,
     @required this.changeProviderOnCheckChange,
     @required this.result,
+    @required this.assetProvider,
     this.initIndex = 0,
+    this.isPreview = false,
   }) : super(key: key);
 
   @override
 }
 
 class _PhotoPreviewPageState extends State<PhotoPreviewPage> {
-  ConfigProvider get config => ConfigProvider.of(context);
+  PhotoPickerProvider get config => PhotoPickerProvider.of(context);
+  AssetProvider get assetProvider => widget.assetProvider;
 
   Options get options => config.options;
 
 
   SelectedProvider get selectedProvider => widget.selectedProvider;
 
-  List<AssetEntity> get list => widget.list;
+  List<AssetEntity> get list {
+    if (!widget.isPreview) {
+      return assetProvider.data;
+    }
+    return widget.list;
+  }
 
   StreamController<int> pageChangeController = StreamController.broadcast();
 
 
   @override
   Widget build(BuildContext context) {
+    int totalCount = assetProvider.current.assetCount ?? 0;
+    if (!widget.isPreview) {
+      totalCount = assetProvider.current.assetCount;
+    } else {
+      totalCount = list.length;
+    }
+
     var data = Theme.of(context);
     var textStyle = TextStyle(
       color: options.textColor,
           title: StreamBuilder(
             stream: pageStream,
             initialData: widget.initIndex,
-            builder: (ctx, snap) => Text(
-                  "${snap.data + 1}/${widget.list.length}",
-                  style: TextStyle(
-                    color: options.textColor,
-                  ),
+            builder: (ctx, snap) {
+              return Text(
+                "${snap.data + 1}/$totalCount",
+                style: TextStyle(
+                  color: options.textColor,
                 ),
+              );
+            },
           ),
           actions: <Widget>[
             StreamBuilder(
               stream: pageStream,
               builder: (ctx, s) => FlatButton(
-                    splashColor: Colors.transparent,
-                    onPressed: selectedList.length == 0 ? null : sure,
-                    child: Text(
-                      config.provider.getSureText(options, selectedList.length),
-                      style: selectedList.length == 0
-                          ? textStyle.copyWith(color: options.disableColor)
-                          : textStyle,
-                    ),
-                  ),
+                splashColor: Colors.transparent,
+                onPressed: selectedList.length == 0 ? null : sure,
+                child: Text(
+                  config.provider.getSureText(options, selectedList.length),
+                  style: selectedList.length == 0
+                      ? textStyle.copyWith(color: options.disableColor)
+                      : textStyle,
+                ),
+              ),
             ),
           ],
         ),
         body: PageView.builder(
           controller: pageController,
           itemBuilder: _buildItem,
-          itemCount: list.length,
+          itemCount: totalCount,
           onPageChanged: _onPageChanged,
         ),
         bottomSheet: _buildThumb(),
   }
 
   Widget _buildItem(BuildContext context, int index) {
+    if (!widget.isPreview && index >= list.length - 5) {
+      _loadMore();
+    }
+
     var data = list[index];
     return BigPhotoImage(
       assetEntity: data,
     );
   }
 
+  Future<void> _loadMore() async {
+    assetProvider.loadMore();
+  }
+
   Widget _buildLoadingWidget(AssetEntity entity) {
     return options.loadingDelegate
         .buildBigImageLoading(context, entity, themeColor);
   Widget _buildThumb() {
     return StreamBuilder(
       builder: (ctx, snapshot) => Container(
-            height: 80.0,
-            child: ListView.builder(
-              itemBuilder: _buildThumbItem,
-              itemCount: previewList.length,
-              scrollDirection: Axis.horizontal,
-            ),
-          ),
+        height: 80.0,
+        child: ListView.builder(
+          itemBuilder: _buildThumbItem,
+          itemCount: previewList.length,
+          scrollDirection: Axis.horizontal,
+        ),
+      ),
       stream: pageStream,
     );
   }

lib/src/ui/photo_app.dart

 
   @override
   Widget build(BuildContext context) {
-    return ConfigProvider(
+    return PhotoPickerProvider(
       provider: provider,
       options: options,
       child: PhotoMainPage(