我正在构建一个带有颤音的天气应用程序，我遇到了这个错误＆quot“实例成员”窗口＆＃x27;可以在初始化器中访问。 ＆quot

Question

我正在构建一个带有颤音的天气应用程序，为此，我必须将位置数据从一个屏幕传输到另一个屏幕，即从Splash屏幕到欢迎屏幕，从欢迎屏幕到Main_screen_navigation，该屏幕具有我的底部导航栏，并从此屏幕到HomeScreen。但是问题在于我必须将位置数据传输到构造函数。也许这就是为什么我遇到这个错误的原因。请帮助我解决这个问题，因为我尝试了所有可能的答案，例如使用Init State。 基本上，我想知道如何将WeatherData从底部导航栏屏幕转移到另一个屏幕。请回答这个问题，我正在寻找2天的答案。 谢谢你！

我的主Screen_Navigation

import 'package:flutter/material.dart';
import 'package:weather_app/utilities/constants.dart';
import 'home_screen.dart';
import 'search_screen.dart';
import 'saved_screen.dart';
import 'forecast_screen.dart';
import 'package:curved_navigation_bar/curved_navigation_bar.dart';

class MainScreenNavigation extends StatefulWidget {
  MainScreenNavigation({required this.locationWeather});
  final locationWeather;

  @override
  State<MainScreenNavigation> createState() => _MainScreenNavigationState();
}

class _MainScreenNavigationState extends State<MainScreenNavigation> {
  int page_number = 0;
  List screens = [
    HomeScreen(locationWeather: widget.weatherData), //here the error is coming 
    SearchScreen(),
    ForecastScreen(),
    SavedScreen(),
  ];
  @override
  void initState() {
    final weather = widget.locationWeather;
    super.initState();
  }

  final items = [
    Icon(
      Icons.home,
      size: 30,
      color: Colors.white,
    ),
    Icon(Icons.search, size: 30, color: Colors.white),
    Icon(Icons.auto_graph, size: 30, color: Colors.white),
    Icon(Icons.favorite, size: 30, color: Colors.white),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      bottomNavigationBar: CurvedNavigationBar(
        backgroundColor: kPrimaryColor,
        color: kPrimaryColor,
        buttonBackgroundColor: kSecondaryColor,
        animationCurve: Curves.fastOutSlowIn,
        height: 60,
        items: items,
        onTap: (index) {
          setState(
            () {
              page_number = index;
            },
          );
        },
      ),
      body: screens[page_number],
    );
  }
}

主屏幕

import 'package:flutter/material.dart';
import 'package:weather_app/utilities/constants.dart';

class HomeScreen extends StatefulWidget {
  HomeScreen({this.locationWeather});
  final locationWeather;
  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: kPrimaryColor,
    );
  }
}

欢迎屏幕

import 'package:flutter/material.dart';
import 'package:weather_app/utilities/constants.dart';
import 'main_screen_navigation.dart';

class WelcomeScreen extends StatefulWidget {
  WelcomeScreen({required this.locationWeather});
  final locationWeather;

  @override
  State<WelcomeScreen> createState() => _WelcomeScreenState();
}

class _WelcomeScreenState extends State<WelcomeScreen> {
  void getLocationData() {
    Navigator.push(
      context,
      MaterialPageRoute(
        builder: (context) {
          return MainScreenNavigation(locationWeather: widget.locationWeather);
        },
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        color: kPrimaryColor,
        child: SafeArea(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              SizedBox(
                height: 120,
              ),
              Image.asset(
                'images/welcome_screen_pic.png',
                height: 250,
              ),
              SizedBox(
                height: 120,
              ),
              Text(
                'Discover the Weather\nin Your City',
                textAlign: TextAlign.center,
                style: kWelcomeScreenTitle,
              ),
              SizedBox(
                height: 20,
              ),
              Text(
                textAlign: TextAlign.center,
                'Get to know your weather maps and\nradar precipitation forecast',
                style: kWelcomeScreenTagLine,
              ),
              SizedBox(
                height: 60,
              ),
              Padding(
                padding: const EdgeInsets.all(8.0),
                child: TextButton(
                  onPressed: () {
                    getLocationData();
                  },
                  child: Container(
                    height: 60,
                    child: Center(
                      child: Text(
                        'Get Started',
                        style: kWelcomeScreenButton,
                      ),
                    ),
                    decoration: BoxDecoration(
                        color: kYellowcolor,
                        borderRadius: BorderRadius.all(Radius.circular(15))),
                  ),
                ),
              )
            ],
          ),
        ),
      ),
    );
  }
}

Answer 1

在主屏导航中，您在初始状态以外的初始天气

  List screens = [];
    

  @override
  void initState() {
screens = [
HomeScreen(locationWeather: widget.weatherData), //here the error is coming 
    SearchScreen(),
    ForecastScreen(),
    SavedScreen(),
  ];
    super.initState();
  }