使用flutter_screenutil遇LateInitializationError问题求助

问题原因 #

你在ScreenUtilInit的child属性中直接传入MaterialApp，且在MaterialApp的theme里使用了.sp、.h这类flutter_screenutil的扩展方法。但theme会在ScreenUtilInit完成初始化之前被构建，导致内部的_minTextAdapt字段未初始化，从而抛出错误。

解决方案 #

改用ScreenUtilInit的builder属性替代child，确保ScreenUtil初始化完成后再构建MaterialApp及其中的theme：

修改后的完整代码：

import 'package:flutter/material.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
import 'package:spoon_app/screens/splash_screen/mobile.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(const Spoon());
}

class Spoon extends StatelessWidget {
  const Spoon({super.key});

  @override
  Widget build(BuildContext context) {
    return ScreenUtilInit(
      designSize: const Size(375, 812),
      minTextAdapt: true,
      splitScreenMode: true,
      // 使用builder替代child，确保ScreenUtil初始化完成后再构建MaterialApp
      builder: (context, child) {
        return MaterialApp(
          theme: ThemeData(
            scaffoldBackgroundColor: const Color(0XFFFFFFFF),
            textTheme: TextTheme(
              bodySmall: TextStyle(
                fontSize: 14.sp,
                fontFamily: "Alex",
                fontWeight: FontWeight.w400,
                height: 1.3.h,
              ),
              bodyMedium: TextStyle(
                fontSize: 12.sp,
                fontFamily: "Alex",
                fontWeight: FontWeight.w700,
              ),
              bodyLarge: const TextStyle(
                color: Colors.white,
                fontSize: 18,
                fontFamily: "Alex",
                fontWeight: FontWeight.w700,
              ),
              headlineMedium: const TextStyle(
                fontSize: 32,
                fontWeight: FontWeight.w500,
              ),
              headlineLarge: TextStyle(
                fontFamily: "Alex",
                fontSize: 32.sp,
                fontWeight: FontWeight.w500,
              )
            ),
          ),
          debugShowCheckedModeBanner: false,
          title: "SpoonApp",
          home: MobileWelcomeScreen(),
        );
      },
    );
  }
}

补充说明 #

builder回调会在ScreenUtil完成所有初始化工作后触发，此时context已包含ScreenUtil的状态，调用.sp、.h等扩展方法时能正常访问到初始化后的_minTextAdapt字段，不会再抛出未初始化错误。

内容的提问来源于stack exchange，提问作者maak akasha