预览页面的修改

lib/src/provider/selected_provider.dart

     return selectedList.remove(entity);
   }
 
+  void compareAndRemoveEntities(List<ImageEntity> previewSelectedList) {
+    var srcList = List.of(selectedList);
+    selectedList.clear();
+    srcList.forEach((entity) {
+      if (previewSelectedList.contains(entity)){
+        selectedList.add(entity);
+      }
+    });
+  }
+
+
   void sure();
 }

lib/src/ui/page/photo_main_page.dart

             options: options,
             galleryName: currentPath.name,
             onGalleryChange: _onGalleryChange,
-            onTapPreview: _onTapPreview,
+            onTapPreview: selectedList.isEmpty ? null : _onTapPreview,
             selectedProvider: this,
             galleryListProvider: this,
           ),
   Widget _buildItem(BuildContext context, int index) {
     var data = list[index];
     return GestureDetector(
-      onTap: () => _onItemClick(data),
+      onTap: () => _onItemClick(data, index),
       child: Stack(
         children: <Widget>[
           ImageItem(
     setState(() {});
   }
 
-  void _onItemClick(ImageEntity data) {}
-
   void _onGalleryChange(ImagePathEntity value) {
     _currentPath = value;
 
     });
   }
 
-  void _onTapPreview() {
+  void _onItemClick(ImageEntity data, int index) {
+    var result = new PhotoPreviewResult();
     Navigator.of(context).push(
+      MaterialPageRoute(
+        builder: (ctx) {
+          return ConfigProvider(
+            provider: ConfigProvider.of(context).provider,
+            options: options,
+            child: PhotoPreviewPage(
+              selectedProvider: this,
+              list: List.of(list),
+              initIndex: index,
+              changeProviderOnCheckChange: true,
+              result: result,
+            ),
+          );
+        },
+      ),
+    ).then((v) {
+      setState(() {});
+    });
+  }
+
+  void _onTapPreview() {
+    var result = new PhotoPreviewResult();
+    Navigator.of(context)
+        .push(
       MaterialPageRoute(
         builder: (ctx) => ConfigProvider(
               provider: ConfigProvider.of(context).provider,
               child: PhotoPreviewPage(
                 selectedProvider: this,
                 list: List.of(selectedList),
+                changeProviderOnCheckChange: false,
+                result: result,
               ),
             ),
       ),
+    )
+        .then(
+      (v) {
+        compareAndRemoveEntities(result.previewSelectedList);
+      },
     );
   }
 }
 
   @override
   Widget build(BuildContext context) {
-    var textStyle = TextStyle(fontSize: 14.0, color: options.textColor);
+    var textStyle = TextStyle(fontSize: 14.0);
     const textPadding = const EdgeInsets.symmetric(horizontal: 16.0);
     return Container(
       color: options.themeColor,
         bottom: true,
         top: false,
         child: Container(
-          height: 44.0,
+          height: 52.0,
           child: Row(
             children: <Widget>[
               GestureDetector(
                   padding: textPadding,
                   child: Text(
                     widget.galleryName,
-                    style: textStyle,
+                    style: textStyle.copyWith(color: options.textColor),
                   ),
                 ),
               ),
               Expanded(
                 child: Container(),
               ),
-              GestureDetector(
-                behavior: HitTestBehavior.translucent,
-                onTap: widget.onTapPreview,
+              FlatButton(
+                onPressed: widget.onTapPreview,
+                textColor: options.textColor,
+                disabledTextColor: options.disableColor,
                 child: Container(
                   height: 44.0,
                   alignment: Alignment.center,

lib/src/ui/page/photo_preview_page.dart

 import 'package:photo/src/entity/options.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';
 import 'package:photo_manager/photo_manager.dart';
 
 class PhotoPreviewPage extends StatefulWidget {
 
   final List<ImageEntity> list;
 
-  const PhotoPreviewPage({Key key, this.selectedProvider, this.list})
-      : super(key: key);
+  final int initIndex;
+
+  /// 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;
+
+  /// 这里封装了结果
+  final PhotoPreviewResult result;
+
+  const PhotoPreviewPage({
+    Key key,
+    @required this.selectedProvider,
+    @required this.list,
+    @required this.changeProviderOnCheckChange,
+    @required this.result,
+    this.initIndex = 0,
+  }) : super(key: key);
 
   @override
   _PhotoPreviewPageState createState() => _PhotoPreviewPageState();
 
   Color get textColor => options.textColor;
 
+  SelectedProvider get selectedProvider => widget.selectedProvider;
+
   List<ImageEntity> get list => widget.list;
 
   StreamController<int> pageChangeController = StreamController.broadcast();
 
+  Stream<int> get pageStream => pageChangeController.stream;
+
+  bool get changeProviderOnCheckChange => widget.changeProviderOnCheckChange;
+
+  List<ImageEntity> get previewSelectedList =>
+      widget.result.previewSelectedList;
+
+  PageController pageController;
+
   @override
   void initState() {
     super.initState();
     pageChangeController.add(0);
+    previewSelectedList.clear();
+    previewSelectedList.addAll(selectedProvider.selectedList);
+    pageController = PageController(
+      initialPage: widget.initIndex,
+    );
   }
 
   @override
         appBar: AppBar(
           backgroundColor: config.options.themeColor,
           title: StreamBuilder(
-            stream: pageChangeController.stream,
-            initialData: 0,
+            stream: pageStream,
+            initialData: widget.initIndex,
             builder: (ctx, snap) => Text(
                   "${snap.data + 1}/${widget.list.length}",
                 ),
           ),
         ),
         body: PageView.builder(
+          controller: pageController,
           itemBuilder: _buildItem,
           itemCount: list.length,
           onPageChanged: _onPageChanged,
         ),
         bottomNavigationBar: _buildBottom(),
+        bottomSheet: _buildThumb(),
       ),
     );
   }
 
   Widget _buildBottom() {
     return Container(
-      height: 44.0,
+      height: 52.0,
       color: themeColor,
+      child: Row(
+        children: <Widget>[
+          Expanded(
+            child: Container(),
+          ),
+          _buildCheckbox(),
+        ],
+      ),
+    );
+  }
+
+  Container _buildCheckbox() {
+    return Container(
+      constraints: BoxConstraints(
+        maxWidth: 150.0,
+      ),
+      child: StreamBuilder<int>(
+        builder: (ctx, snapshot) {
+          var index = snapshot.data;
+          var data = list[index];
+          return CheckboxListTile(
+            value: previewSelectedList.contains(data),
+            onChanged: (bool check) {
+              if (changeProviderOnCheckChange) {
+                _onChangeProvider(check, index);
+              } else {
+                _onCheckInOnlyPreview(check, index);
+              }
+            },
+            activeColor: Color.lerp(textColor, themeColor, 0.6),
+            title: Text(
+              config.provider.getSelectedOptionsText(options),
+              textAlign: TextAlign.end,
+              style: TextStyle(color: options.textColor),
+            ),
+          );
+        },
+        initialData: widget.initIndex,
+        stream: pageStream,
+      ),
     );
   }
 
+  /// 仅仅修改预览时的状态,在退出时,再更新provider的顺序,这里无论添加与否不修改顺序
+  void _onCheckInOnlyPreview(bool check, int index) {
+    var item = list[index];
+    if (check) {
+      previewSelectedList.add(item);
+    } else {
+      previewSelectedList.remove(item);
+    }
+    pageChangeController.add(index);
+  }
+
+  /// 直接修改预览状态,会直接移除item
+  void _onChangeProvider(bool check, int index) {
+    var item = list[index];
+    if (check) {
+      if (selectedProvider.addSelectEntity(item)) {
+        previewSelectedList.add(item);
+      }
+    } else {
+      selectedProvider.removeSelectEntity(item);
+      previewSelectedList.remove(item);
+    }
+    pageChangeController.add(index);
+  }
+
   Widget _buildItem(BuildContext context, int index) {
     var data = list[index];
     return BigPhotoImage(
   void _onPageChanged(int value) {
     pageChangeController.add(value);
   }
+
+  Widget _buildThumb() {
+    return Container(
+      height: 80.0,
+      child: ListView.builder(
+        itemBuilder: _buildThumbItem,
+        itemCount: previewSelectedList.length,
+        scrollDirection: Axis.horizontal,
+      ),
+    );
+  }
+
+  Widget _buildThumbItem(BuildContext context, int index) {
+    // todo 这里需要一个遮盖
+    var item = previewSelectedList[index];
+    return GestureDetector(
+      onTap: () => changeSelected(item, index),
+      child: Container(
+        width: 80.0,
+        child: ImageItem(
+          themeColor: themeColor,
+          entity: item,
+        ),
+      ),
+    );
+  }
+
+  void changeSelected(ImageEntity entity, int index) {
+    var itemIndex = list.indexOf(entity);
+    if (itemIndex != -1) pageController.jumpToPage(itemIndex);
+  }
 }
 
 class BigPhotoImage extends StatefulWidget {
   @override
   bool get wantKeepAlive => true;
 }
+
+class PhotoPreviewResult {
+  List<ImageEntity> previewSelectedList = [];
+}