feature：适配深色模式，现仅支持跟随系统

lib/main.dart

@@ -1,18 +1,18 @@
 import 'package:flutter/material.dart';
 import 'package:fluro/fluro.dart';
+import 'package:flutter_picgo/resources/theme_colors.dart';
 import 'package:flutter_picgo/routers/application.dart';
 import 'package:flutter_picgo/routers/routers.dart';
 import 'package:flutter_picgo/utils/db_provider.dart';
 
 void main() async {
-  WidgetsFlutterBinding.ensureInitialized(); 
+  WidgetsFlutterBinding.ensureInitialized();
   final provider = DbProvider();
   await provider.init();
   runApp(App());
 }
 
 class App extends StatelessWidget {
-
   App() {
     final router = new Router();
     Routes.configureRoutes(router);
@@ -24,24 +24,10 @@ class App extends StatelessWidget {
   Widget build(BuildContext context) {
     return MaterialApp(
       debugShowCheckedModeBanner: false,
-      theme: ThemeData(
-        // This is the theme of your application.
-        //
-        // Try running your application with "flutter run". You'll see the
-        // application has a blue toolbar. Then, without quitting the app, try
-        // changing the primarySwatch below to Colors.green and then invoke
-        // "hot reload" (press "r" in the console where you ran "flutter run",
-        // or simply save your changes to "hot reload" in a Flutter IDE).
-        // Notice that the counter didn't reset back to zero; the application
-        // is not restarted.
-        primarySwatch: Colors.blue,
-        // This makes the visual density adapt to the platform that you run
-        // the app on. For desktop platforms, the controls will be smaller and
-        // closer together (more dense) than on mobile platforms.
-        visualDensity: VisualDensity.adaptivePlatformDensity,
-      ),
+      theme: lightThemeData,
+      darkTheme: darkThemeData,
       initialRoute: '/',
       onGenerateRoute: Application.router.generator,
     );
   }
-}
+}