🐛 Make sort delegate a static constant same as text delegate.

Related to #24 .

Author: AlexV525

lib/src/constants/constants.dart

@@ -2,7 +2,7 @@
 /// [Author] Alex (https://github.com/AlexVincent525)
 /// [Date] 2020/3/31 16:02
 ///
-import '../delegates/text_delegate.dart';
+import 'constants.dart';
 
 export '../delegates/sort_path_delegate.dart';
 export '../delegates/text_delegate.dart';
@@ -16,4 +16,5 @@ class Constants {
   const Constants._();
 
   static TextDelegate textDelegate = DefaultTextDelegate();
+  static SortPathDelegate sortPathDelegate = SortPathDelegate.common;
 }

lib/src/provider/asset_picker_provider.dart

@@ -27,6 +27,7 @@ class AssetPickerProvider extends ChangeNotifier {
     if (selectedAssets?.isNotEmpty ?? false) {
       _selectedAssets = List<AssetEntity>.from(selectedAssets);
     }
+    Constants.sortPathDelegate = sortPathDelegate ?? SortPathDelegate.common;
     Future<void>.delayed(routeDuration).then(
       (dynamic _) async {
         await getAssetPathList();
@@ -212,7 +213,7 @@ class AssetPickerProvider extends ChangeNotifier {
     );
 
     /// Sort path using sort path delegate.
-    sortPathDelegate.sort(_list);
+    Constants.sortPathDelegate.sort(_list);
 
     for (final AssetPathEntity pathEntity in _list) {
       // Use sync method to avoid unnecessary wait.