✨ Implement the default light theme (#234)

Author: AlexV525

example/lib/constants/picker_method.dart

@@ -317,6 +317,25 @@ class PickMethod {
     );
   }
 
+  factory PickMethod.customizableTheme(int maxAssetsCount) {
+    return PickMethod(
+      icon: '🎨',
+      name: 'Customizable theme',
+      description: 'Picking assets with the light theme with different color.',
+      method: (BuildContext context, List<AssetEntity> assets) {
+        return AssetPicker.pickAssets(
+          context,
+          maxAssets: maxAssetsCount,
+          selectedAssets: assets,
+          pickerTheme: AssetPicker.themeData(
+            Colors.lightBlueAccent,
+            light: true,
+          ),
+        );
+      },
+    );
+  }
+
   final String icon;
   final String name;
   final String description;

example/lib/pages/multi_assets_page.dart

@@ -48,6 +48,7 @@ class _MultiAssetsPageState extends State<MultiAssetsPage>
         },
       ),
       PickMethod.noPreview(maxAssetsCount),
+      PickMethod.customizableTheme(maxAssetsCount),
       PickMethod.customFilterOptions(maxAssetsCount),
       PickMethod.preventGIFPicked(maxAssetsCount),
       PickMethod.keepScrollOffset(

example/lib/pages/single_assets_page.dart

@@ -39,6 +39,7 @@ class _SingleAssetPageState extends State<SingleAssetPage>
       PickMethod.customFilterOptions(maxAssetsCount),
       PickMethod.preventGIFPicked(maxAssetsCount),
       PickMethod.noPreview(maxAssetsCount),
+      PickMethod.customizableTheme(maxAssetsCount),
     ];
   }
 

lib/src/delegates/asset_picker_builder_delegate.dart

@@ -759,11 +759,11 @@ class DefaultAssetPickerBuilderDelegate
 
   /// [Duration] when triggering path switching.
   /// 切换路径时的动画时长
-  Duration get switchingPathDuration => kThemeAnimationDuration;
+  Duration get switchingPathDuration => const Duration(milliseconds: 300);
 
   /// [Curve] when triggering path switching.
   /// 切换路径时的动画曲线
-  Curve get switchingPathCurve => Curves.easeInOut;
+  Curve get switchingPathCurve => Curves.easeInOutQuad;
 
   /// Whether the [SpecialPickerType.wechatMoment] is enabled.
   /// 当前是否为微信朋友圈选择模式

lib/src/delegates/asset_picker_viewer_builder_delegate.dart

@@ -983,7 +983,7 @@ class DefaultAssetPickerViewerBuilderDelegate
                   ? SystemUiOverlayStyle.light
                   : SystemUiOverlayStyle.dark),
           child: Material(
-            color: Colors.black,
+            color: themeData.colorScheme.onSecondary,
             child: Stack(
               children: <Widget>[
                 Positioned.fill(child: _pageViewBuilder(context)),

lib/src/widget/asset_picker.dart

@@ -199,7 +199,50 @@ class AssetPicker<Asset, Path> extends StatefulWidget {
 
   /// Build a dark theme according to the theme color.
   /// 通过主题色构建一个默认的暗黑主题
-  static ThemeData themeData(Color themeColor) {
+  static ThemeData themeData(Color themeColor, {bool light = false}) {
+    if (light) {
+      return ThemeData.light().copyWith(
+        primaryColor: Colors.grey[50],
+        primaryColorBrightness: Brightness.dark,
+        primaryColorLight: Colors.grey[50],
+        primaryColorDark: Colors.grey[50],
+        canvasColor: Colors.grey[100],
+        scaffoldBackgroundColor: Colors.grey[50],
+        bottomAppBarColor: Colors.grey[50],
+        cardColor: Colors.grey[50],
+        highlightColor: Colors.transparent,
+        toggleableActiveColor: themeColor,
+        textSelectionTheme: TextSelectionThemeData(
+          cursorColor: themeColor,
+          selectionColor: themeColor.withAlpha(100),
+          selectionHandleColor: themeColor,
+        ),
+        indicatorColor: themeColor,
+        appBarTheme: const AppBarTheme(
+          systemOverlayStyle: SystemUiOverlayStyle(
+            statusBarBrightness: Brightness.light,
+            statusBarIconBrightness: Brightness.dark,
+          ),
+          elevation: 0,
+        ),
+        buttonTheme: ButtonThemeData(buttonColor: themeColor),
+        colorScheme: ColorScheme(
+          primary: Colors.grey[50]!,
+          primaryVariant: Colors.grey[50]!,
+          secondary: themeColor,
+          secondaryVariant: themeColor,
+          background: Colors.grey[50]!,
+          surface: Colors.grey[50]!,
+          brightness: Brightness.light,
+          error: const Color(0xffcf6679),
+          onPrimary: Colors.white,
+          onSecondary: Colors.white,
+          onSurface: Colors.black,
+          onBackground: Colors.black,
+          onError: Colors.white,
+        ),
+      );
+    }
     return ThemeData.dark().copyWith(
       primaryColor: Colors.grey[900],
       primaryColorBrightness: Brightness.dark,