🐛 Fix view assets with only selected (#546)

Fixes #536

Author: AlexV525

CHANGELOG.md

@@ -13,6 +13,10 @@ that can be found in the LICENSE file. -->
 
 - Use `wechat_picker_library`.
 
+### Fixes
+
+- Fix previewing selected assets behavior.
+
 ## 9.0.0-dev.2
 
 ### Fixes

example/lib/customs/pickers/directory_file_asset_picker.dart

@@ -381,8 +381,8 @@ class FileAssetPickerBuilder
   @override
   Future<void> viewAsset(
     BuildContext context,
-    int index,
-    AssetEntity currentAsset,
+    int? index,
+    File currentAsset,
   ) async {
     final List<File>? result = await Navigator.of(context).push<List<File>?>(
       PageRouteBuilder<List<File>>(
@@ -393,7 +393,8 @@ class FileAssetPickerBuilder
         ) {
           return AssetPickerViewer<File, Directory>(
             builder: FileAssetPickerViewerBuilderDelegate(
-              currentIndex: index,
+              currentIndex:
+                  index ?? provider.selectedAssets.indexOf(currentAsset),
               previewAssets: provider.selectedAssets,
               provider: FileAssetPickerViewerProvider(provider.selectedAssets),
               themeData: AssetPicker.themeData(themeColor),

example/lib/customs/pickers/insta_asset_picker.dart

@@ -378,9 +378,12 @@ class InstaAssetPickerBuilder extends DefaultAssetPickerBuilderDelegate {
   @override
   Future<void> viewAsset(
     BuildContext context,
-    int index,
+    int? index,
     AssetEntity currentAsset,
   ) async {
+    if (index == null) {
+      return;
+    }
     // if is preview asset, unselect it
     if (provider.selectedAssets.isNotEmpty &&
         _previewAsset.value == currentAsset) {

guides/migration_guide.md

@@ -19,7 +19,14 @@ This document gathered all breaking changes and migrations requirement between m
 
 ## 9.0.0
 
-### Summary
+### View assets signature change
+
+`AssetPickerBuilderDelegate.viewAsset` has 2 changes:
+- It now uses the generic type of the delegate rather than always `AssetEntity`.
+- The `index` of arguments is now nullable,
+  to indicate the behavior of previewing selected assets only.
+
+### Permission request option integration
 
 `PermissionRequestOption` has been added to
 `AssetPickerDelegate.permissionCheck` and
@@ -28,7 +35,7 @@ Classes that extend `AssetPickerDelegate` and override these methods must migrat
 Delegates that use `AssetPicker.permissionCheck`
 should choose whether to pass the request option.
 
-### Details
+#### Details
 
 Before:
 

lib/src/delegates/asset_picker_builder_delegate.dart

@@ -242,11 +242,7 @@ abstract class AssetPickerBuilderDelegate<Asset, Path> {
 
   /// Determine how to browse assets in the viewer.
   /// 定义如何在查看器中浏览资源
-  Future<void> viewAsset(
-    BuildContext context,
-    int index,
-    AssetEntity currentAsset,
-  );
+  Future<void> viewAsset(BuildContext context, int? index, Asset currentAsset);
 
   /// Yes, the build method.
   /// 没错，是它是它就是它，我们亲爱的 build 方法~
@@ -870,7 +866,7 @@ class DefaultAssetPickerBuilderDelegate
   @override
   Future<void> viewAsset(
     BuildContext context,
-    int index,
+    int? index,
     AssetEntity currentAsset,
   ) async {
     final DefaultAssetPickerProvider provider =
@@ -902,6 +898,10 @@ class DefaultAssetPickerBuilderDelegate
         selected = provider.selectedAssets;
         effectiveIndex = current.indexOf(currentAsset);
       }
+    } else if (index == null) {
+      current = provider.selectedAssets;
+      selected = provider.selectedAssets;
+      effectiveIndex = selected.indexOf(currentAsset);
     } else {
       current = provider.currentAssets;
       selected = provider.selectedAssets;
@@ -1936,7 +1936,7 @@ class DefaultAssetPickerBuilderDelegate
       child: Consumer<DefaultAssetPickerProvider>(
         builder: (context, DefaultAssetPickerProvider p, __) => GestureDetector(
           onTap: p.isSelectedNotEmpty
-              ? () => viewAsset(context, 0, p.selectedAssets.first)
+              ? () => viewAsset(context, null, p.selectedAssets.first)
               : null,
           child: Selector<DefaultAssetPickerProvider, String>(
             selector: (_, DefaultAssetPickerProvider p) =>