add sort asset delegate

lib/src/delegate/sort_asset_delegate.dart

+part of './sort_delegate.dart';
+
+abstract class SortAssetDelegate {
+  const SortAssetDelegate();
+
+  void sort(List<AssetEntity> list);
+}
+
+class DefaultAssetDelegate extends SortAssetDelegate {
+  const DefaultAssetDelegate();
+
+  @override
+  void sort(List<AssetEntity> list) {
+    list.sort((entity1, entity2) {
+      return entity2.createTime.compareTo(entity1.createTime);
+    });
+  }
+}

lib/src/delegate/sort_delegate.dart

 import 'package:photo_manager/photo_manager.dart';
 
+part './sort_asset_delegate.dart';
+
+/// SortPathDelegate
 abstract class SortDelegate {
-  const SortDelegate();
+  final SortAssetDelegate assetDelegate;
+
+  const SortDelegate({
+    this.assetDelegate = const DefaultAssetDelegate(),
+  });
 
   void sort(List<AssetPathEntity> list);
 
 }
 
 class DefaultSortDelegate extends SortDelegate {
-  const DefaultSortDelegate();
+  const DefaultSortDelegate({
+    SortAssetDelegate assetDelegate = const DefaultAssetDelegate(),
+  }) : super(assetDelegate: assetDelegate);
 
   @override
   void sort(List<AssetPathEntity> list) {}
 }
 
 class CommonSortDelegate extends SortDelegate {
-  const CommonSortDelegate();
+  const CommonSortDelegate({
+    SortAssetDelegate assetDelegate = const DefaultAssetDelegate(),
+  }) : super(assetDelegate: assetDelegate);
 
   @override
   void sort(List<AssetPathEntity> list) {

lib/src/ui/page/photo_main_page.dart

     galleryPathList.addAll(widget.photoList);
     this.list.clear();
     var assetList = await galleryPathList[0].assetList;
+    _sortAssetList(assetList);
     this.list.addAll(assetList);
     setState(() {
       _isInit = true;
 
     if (pathList.isNotEmpty) {
       imageList = await pathList[0].assetList;
+      _sortAssetList(imageList);
       _currentPath = pathList[0];
     }
 
     });
   }
 
+  void _sortAssetList(List<AssetEntity> assetList) {
+    options?.sortDelegate?.assetDelegate?.sort(assetList);
+  }
+
   Widget _buildBody() {
     if (!_isInit) {
       return _buildLoading();
     _currentPath = value;
 
     _currentPath.assetList.then((v) {
+      _sortAssetList(v);
       list.clear();
       list.addAll(v);
       scrollController.jumpTo(0.0);