✨ Add SpecialPickerType.

Fix #37 .

Author: AlexV525

example/lib/pages/single_assets_page.dart

@@ -131,6 +131,23 @@ class _SingleAssetPageState extends State<SingleAssetPage> {
             );
           },
         ),
+        PickMethodModel(
+          icon: '🎭',
+          name: 'Wechat moment',
+          description: 'Pick assets just like the wechat moment pattern.',
+          method: (
+            BuildContext context,
+            List<AssetEntity> assets,
+          ) async {
+            return await AssetPicker.pickAssets(
+              context,
+              maxAssets: maxAssetsCount,
+              selectedAssets: assets,
+              themeColor: themeColor,
+              specialPickerType: SpecialPickerType.wechatMoment,
+            );
+          },
+        ),
       ];
 
   Future<void> selectAssets(PickMethodModel model) async {

lib/src/constants/constants.dart

@@ -11,6 +11,7 @@ export '../delegates/text_delegate.dart';
 
 export 'colors.dart';
 export 'custom_scroll_physics.dart';
+export 'enums.dart';
 
 class Constants {
   const Constants._();

lib/src/constants/enums.dart

@@ -0,0 +1,9 @@
+///
+/// [Author] Alex (https://github.com/AlexVincent525)
+/// [Date] 2020/7/8 12:32
+///
+
+/// Provide some special picker types to integrate
+/// un-common pick pattern.
+/// 提供一些特殊的选择器类型以整合非常规的选择行为。
+enum SpecialPickerType { wechatMoment }

lib/src/constants/zoom_page_transition.dart

@@ -119,7 +119,7 @@ class _ZoomPageTransitionState extends State<ZoomPageTransition> {
       builder: (BuildContext context, Widget child) {
         if (widget.animation.status == AnimationStatus.forward ||
             _transitionWasInterrupted) {
-          return Container(
+          return ColoredBox(
             color:
                 Colors.black.withOpacity(_forwardScrimOpacityAnimation.value),
             child: FadeTransition(

lib/src/widget/asset_picker.dart

@@ -7,8 +7,8 @@ import 'dart:math' as math;
 import 'dart:typed_data';
 import 'dart:ui' as ui;
 
-import 'package:flutter/material.dart';
 import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:extended_image/extended_image.dart';
 import 'package:photo_manager/photo_manager.dart';
@@ -28,6 +28,7 @@ class AssetPicker extends StatelessWidget {
     int gridCount = 4,
     Color themeColor,
     TextDelegate textDelegate,
+    this.specialPickerType,
   })  : assert(
           provider != null,
           'AssetPickerProvider must be provided and not null.',
@@ -63,6 +64,17 @@ class AssetPicker extends StatelessWidget {
   /// 通常情况下微信选择器使用的是暗色（暗色背景）的主题，但某些情况下开发者需要亮色或自定义主题。
   final ThemeData pickerTheme;
 
+  /// The current special picker type for the viewer.
+  /// 当前特殊选择类型
+  ///
+  /// There're several types which are special:
+  /// * [SpecialPickerType.wechatMoment] When user selected video, no more images
+  /// can be selected.
+  ///
+  /// 这里包含一些特殊选择类型：
+  /// * [SpecialPickerType.wechatMoment] 微信朋友圈模式。当用户选择了视频，将不能选择图片。
+  final SpecialPickerType specialPickerType;
+
   /// Static method to push with the navigator.
   /// 跳转至选择器的静态方法
   static Future<List<AssetEntity>> pickAssets(
@@ -72,7 +84,8 @@ class AssetPicker extends StatelessWidget {
     int pageSize = 320,
     int pathThumbSize = 200,
     int gridCount = 4,
-    RequestType requestType = RequestType.image,
+    RequestType requestType,
+    SpecialPickerType specialPickerType,
     List<AssetEntity> selectedAssets,
     Color themeColor,
     ThemeData pickerTheme,
@@ -82,15 +95,32 @@ class AssetPicker extends StatelessWidget {
     Duration routeDuration = const Duration(milliseconds: 300),
   }) async {
     if (maxAssets == null || maxAssets < 1) {
-      throw ArgumentError('maxAssets must be greater than 1.');
+      throw ArgumentError(
+        'maxAssets must be greater than 1.',
+      );
     }
     if (pageSize != null && pageSize % gridCount != 0) {
-      throw ArgumentError('pageSize must be a multiple of gridCount.');
+      throw ArgumentError(
+        'pageSize must be a multiple of gridCount.',
+      );
     }
     if (pickerTheme != null && themeColor != null) {
       throw ArgumentError(
-          'Theme and theme color cannot be set at the same time.');
+        'Theme and theme color cannot be set at the same time.',
+      );
     }
+    if (specialPickerType != null && requestType != null) {
+      throw ArgumentError(
+        'specialPickerType and requestType cannot be set at the same time.',
+      );
+    } else {
+      if (specialPickerType == SpecialPickerType.wechatMoment) {
+        requestType = RequestType.common;
+      } else {
+        requestType ??= RequestType.image;
+      }
+    }
+
     try {
       final bool isPermissionGranted = await PhotoManager.requestPermission();
       if (isPermissionGranted) {
@@ -110,6 +140,7 @@ class AssetPicker extends StatelessWidget {
           textDelegate: textDelegate,
           themeColor: themeColor,
           pickerTheme: pickerTheme,
+          specialPickerType: specialPickerType,
         );
         final List<AssetEntity> result = await Navigator.of(
           context,
@@ -272,7 +303,7 @@ class AssetPicker extends StatelessWidget {
                       ),
                     Padding(
                       padding: const EdgeInsets.only(left: 5.0),
-                      child: Container(
+                      child: DecoratedBox(
                         decoration: BoxDecoration(
                           shape: BoxShape.circle,
                           color: theme.iconTheme.color.withOpacity(0.5),
@@ -665,13 +696,19 @@ class AssetPicker extends StatelessWidget {
         final bool selected = selectedAssets.contains(asset);
         return Positioned.fill(
           child: GestureDetector(
-            onTap: () {
-              AssetPickerViewer.pushToViewer(
+            onTap: () async {
+              final List<AssetEntity> result =
+                  await AssetPickerViewer.pushToViewer(
                 context,
                 currentIndex: index,
                 assets: provider.currentAssets,
                 themeData: theme,
+                specialPickerType:
+                    asset.type == AssetType.video ? specialPickerType : null,
               );
+              if (result != null) {
+                Navigator.of(context).pop(result);
+              }
             },
             child: AnimatedContainer(
               duration: switchingPathDuration,
@@ -766,7 +803,7 @@ class AssetPicker extends StatelessWidget {
 
   /// [GridView] for assets under [AssetPickerProvider.currentPathEntity].
   /// 正在查看的目录下的资源网格部件
-  Widget assetsGrid(BuildContext context) => Container(
+  Widget assetsGrid(BuildContext context) => ColoredBox(
         color: theme.canvasColor,
         child: Selector<AssetPickerProvider, List<AssetEntity>>(
           selector: (BuildContext _, AssetPickerProvider provider) =>
@@ -811,7 +848,9 @@ class AssetPicker extends StatelessWidget {
                 return Stack(
                   children: <Widget>[
                     builder,
-                    _selectIndicator(asset),
+                    if (specialPickerType != SpecialPickerType.wechatMoment ||
+                        asset.type != AssetType.video)
+                      _selectIndicator(asset),
                   ],
                 );
               },
@@ -876,7 +915,7 @@ class AssetPicker extends StatelessWidget {
           Widget loader;
           switch (state.extendedImageLoadState) {
             case LoadState.loading:
-              loader = Container(color: const Color(0x10ffffff));
+              loader = const ColoredBox(color: Color(0x10ffffff));
               break;
             case LoadState.completed:
               SpecialImageType type;

lib/src/widget/asset_picker_viewer.dart

@@ -30,6 +30,7 @@ class AssetPickerViewer extends StatefulWidget {
     @required this.themeData,
     this.selectedAssets,
     this.selectorProvider,
+    this.specialPickerType,
   }) : super(key: key);
 
   /// Current previewing index in assets.
@@ -52,6 +53,13 @@ class AssetPickerViewer extends StatefulWidget {
   /// 主题
   final ThemeData themeData;
 
+  /// The current special picker type for the viewer.
+  /// 当前特殊选择类型
+  ///
+  /// If the type is not null, the title of the viewer will not display.
+  /// 如果类型不为空，则标题将不会显示。
+  final SpecialPickerType specialPickerType;
+
   @override
   AssetPickerViewerState createState() => AssetPickerViewerState();
 
@@ -64,6 +72,7 @@ class AssetPickerViewer extends StatefulWidget {
     @required ThemeData themeData,
     List<AssetEntity> selectedAssets,
     AssetPickerProvider selectorProvider,
+    SpecialPickerType specialPickerType,
   }) async {
     try {
       final Widget viewer = AssetPickerViewer(
@@ -72,6 +81,7 @@ class AssetPickerViewer extends StatefulWidget {
         themeData: themeData,
         selectedAssets: selectedAssets,
         selectorProvider: selectorProvider,
+        specialPickerType: specialPickerType,
       );
       final PageRouteBuilder<List<AssetEntity>> pageRoute =
           PageRouteBuilder<List<AssetEntity>>(
@@ -302,7 +312,7 @@ class AssetPickerViewerState extends State<AssetPickerViewer>
           child: Row(
             children: <Widget>[
               const BackButton(),
-              if (!isAppleOS)
+              if (!isAppleOS && widget.specialPickerType == null)
                 StreamBuilder<int>(
                   initialData: currentIndex,
                   stream: pageStreamController.stream,
@@ -318,7 +328,9 @@ class AssetPickerViewerState extends State<AssetPickerViewer>
                 ),
               const Spacer(),
               if (isAppleOS && provider != null) selectButton,
-              if (!isAppleOS && provider != null) confirmButton(context),
+              if (!isAppleOS && provider != null ||
+                  widget.specialPickerType == SpecialPickerType.wechatMoment)
+                confirmButton(context),
             ],
           ),
         ),
@@ -341,30 +353,61 @@ class AssetPickerViewerState extends State<AssetPickerViewer>
             Widget __,
           ) {
             return MaterialButton(
-              minWidth: provider.isSelectedNotEmpty ? 48.0 : 20.0,
+              minWidth: () {
+                if (widget.specialPickerType ==
+                    SpecialPickerType.wechatMoment) {
+                  return 48.0;
+                }
+                return provider.isSelectedNotEmpty ? 48.0 : 20.0;
+              }(),
               height: 32.0,
               padding: const EdgeInsets.symmetric(horizontal: 12.0),
-              color: provider.isSelectedNotEmpty
-                  ? widget.themeData.colorScheme.secondary
-                  : widget.themeData.dividerColor,
+              color: () {
+                if (widget.specialPickerType ==
+                    SpecialPickerType.wechatMoment) {
+                  return widget.themeData.colorScheme.secondary;
+                }
+                return provider.isSelectedNotEmpty
+                    ? widget.themeData.colorScheme.secondary
+                    : widget.themeData.dividerColor;
+              }(),
               shape: RoundedRectangleBorder(
                 borderRadius: BorderRadius.circular(3.0),
               ),
               child: Text(
-                provider.isSelectedNotEmpty
-                    ? '${Constants.textDelegate.confirm}(${provider.currentlySelectedAssets.length}'
+                () {
+                  if (widget.specialPickerType ==
+                      SpecialPickerType.wechatMoment) {
+                    return Constants.textDelegate.confirm;
+                  }
+                  if (provider.isSelectedNotEmpty) {
+                    return '${Constants.textDelegate.confirm}'
+                        '(${provider.currentlySelectedAssets.length}'
                         '/'
-                        '${widget.selectorProvider.maxAssets})'
-                    : Constants.textDelegate.confirm,
+                        '${widget.selectorProvider.maxAssets})';
+                  }
+                  return Constants.textDelegate.confirm;
+                }(),
                 style: TextStyle(
-                  color: provider.isSelectedNotEmpty
-                      ? widget.themeData.textTheme.bodyText1.color
-                      : widget.themeData.textTheme.caption.color,
+                  color: () {
+                    if (widget.specialPickerType ==
+                        SpecialPickerType.wechatMoment) {
+                      return widget.themeData.textTheme.bodyText1.color;
+                    }
+                    return provider.isSelectedNotEmpty
+                        ? widget.themeData.textTheme.bodyText1.color
+                        : widget.themeData.textTheme.caption.color;
+                  }(),
                   fontSize: 17.0,
                   fontWeight: FontWeight.normal,
                 ),
               ),
               onPressed: () {
+                if (widget.specialPickerType ==
+                    SpecialPickerType.wechatMoment) {
+                  Navigator.of(context).pop(<AssetEntity>[currentAsset]);
+                  return;
+                }
                 if (provider.isSelectedNotEmpty) {
                   Navigator.of(context).pop(provider.currentlySelectedAssets);
                 }

lib/wechat_assets_picker.dart

@@ -1,8 +1,9 @@
 library wechat_assets_picker;
 
 export 'package:photo_manager/photo_manager.dart'
-    show AssetEntity, RequestType, AssetType;
+    show AssetEntity, AssetType, RequestType;
 
+export 'src/constants/enums.dart';
 export 'src/delegates/sort_path_delegate.dart';
 export 'src/delegates/text_delegate.dart';
 export 'src/provider/asset_entity_image_provider.dart';