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flutter - 未处理的异常：NoSuchMethodError：类'String'没有实例方法'subString'

问题描述

我无法找到这个问题的解决方案，我的错误是字符串没有包含子字符串的实例。我想打印变量“现在”，但它显示了这个错误。我尝试了很多与这个问题匹配的解决方案，但它没有帮助我。请帮助我错误：E/flutter（6091）：[错误：flutter/ lib/ui/ui_dart_state.cc(186)] 未处理的异常：NoSuchMethodError：类'String'没有实例方法'SubString'。E/flutter (6091): 接收者: "+01:00" E/flutter (6091): 尝试调用: subString(1, 3) E/flutter (6091): #0 Object.noSuchMethod (dart:core-patch/ object_patch.dart:54:5) E/flutter (6091): #1 _LoadingState.getTime (package:world_time/pages/loading.dart:22:40) E/flutter (6091):

import 'package:flutter/material.dart';
import 'package:http/http.dart';
import 'dart:convert';
import 'dart:core';

class Loading extends StatefulWidget {
  @override
  _LoadingState createState() => _LoadingState();
}

class _LoadingState extends State<Loading> {


  void getTime() async {
    //make the request
    Response response = await get(Uri.parse('https://worldtimeapi.org/api/timezone/Europe/London'));
    Map data =jsonDecode(response.body);
    //print(data);

    //get property from data
    String datetime =data['datetime'];
    String offset = data['utc_offset'].subString(1,3);
    //print(datetime);
    //print(offset);

    //create a datetime object
    DateTime now =DateTime.parse(datetime);
    now =now.add(Duration(hours: int.parse(offset)));
    print(now);




  }

  @override
  void initState() {
    super.initState();
    getTime();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Text('loading screen'),
    );
  }
}

标签： flutter

解决方案

尝试将其更改为：

String offset = data['utc_offset'].toString().substring(1,3);

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