在我的简单项目中，有一个按钮可以将主题从浅色变为深色，反之亦然，如下所示:import'package:flutter/material.dart';import'package:shared_preferences/shared_preferences.dart';import'dart:async';voidmain()=>runApp(MyApp());classMyAppextendsStatefulWidget{@overrideMyAppStatecreateState(){returnnewMyAppState();}}classMyAppStateextendsStat
