01.修改手机顶部状态栏样式

import 'package:flutter/services.dart';
SystemUiOverlayStyle systemUiOverlayStyle = const SystemUiOverlayStyle(
    statusBarColor:Colors.transparent, // 设置状态栏背景为透明色
    statusBarIconBrightness: Brightness.light, // 设置状态栏颜色为白色; Brightness.dark 设置字体为黑色
);
SystemChrome.setSystemUIOverlayStyle(systemUiOverlayStyle);