factor:布局颜色重构

lib/pages/category_page.dart

@@ -38,13 +38,11 @@ class _CategoryPageState extends State<CategoryPage> {
         Expanded(
           child: ListView.separated(
             itemCount: provider.categoryList.length,
+            separatorBuilder: (context, index) => SizedBox(height: 8),
             itemBuilder: (context, index) {
               final category = provider.categoryList[index];
               return buildCategoryCard(context, category);
             },
-            separatorBuilder: (BuildContext context, int index) {
-              return SizedBox(height: 8);
-            },
           ),
         ),
       ],