Flutter：如何存储位置数据？

Question

错误：

1. 命名参数“locationData”是必需的，但没有 对应的论据。尝试添加所需的参数。

2. 未定义的名称'locationData'。尝试将名称更正为已定义的名称，或定义名称。

   main.dart文件中的位置数据报错请帮我解决。

   我的代码：

   下面是导致错误的main.dart 代码：

   import 'package:firebase_core/firebase_core.dart';
   import 'package:firstapp/screens/Login_screen.dart';
   import 'package:firstapp/screens/authunication/phone_auth_screen.dart';
   import 'package:firstapp/screens/home_screen.dart';
   import 'package:firstapp/screens/location_screen.dart';
   import 'package:firstapp/screens/splash_screen.dart';
   import 'package:flutter/material.dart';
   import 'package:location/location.dart';
   
   Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
   await Firebase.initializeApp();
    runApp(MyApp());
    }
    
   
   // ignore: use_key_in_widget_constructors
   class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
   return MaterialApp(
     debugShowCheckedModeBanner: false,
     theme: ThemeData(
       primaryColor: Colors.cyan.shade900,
     ),
     initialRoute: SplashScreen.id,
     routes: {
       SplashScreen.id: (context) => SplashScreen(),
       LoginScreen.id: (context) => LoginScreen(),
       PhoneAuthScreen.id: (context) => PhoneAuthScreen(),
       LocationScreen.id: (context) => LocationScreen(),
       HomeScreen.id: (context) => HomeScreen(locationData),
     },
   );`
   

   下面是我想要位置数据的HomeScreen 小部件的代码：

   import 'package:flutter/material.dart';
   import 'package:location/location.dart';
   
    class HomeScreen extends StatelessWidget {
    static const String id = 'home-screen';
    final LocationData locationData;
    HomeScreen({
    required this.locationData, 
    });
    @override
    Widget build(BuildContext context) {
    return Scaffold(
     appBar: AppBar(
       title: Text(locationData.latitude.toString()),
     ),
     body: Center(
       child: Text('Home screen'),
     ),
     );
      }
     }
   

   这是应用程序中LocationScreen 小部件的代码：

   import 'package:firebase_auth/firebase_auth.dart';
   import 'package:firstapp/screens/login_screen.dart';
   import 'package:flutter/cupertino.dart';
   import 'package:flutter/material.dart';
   import 'package:location/location.dart';
   
   
   
   class LocationScreen extends StatefulWidget {
   static const String id = 'location-screen';
   
   @override
   State<LocationScreen> createState() => _LocationScreenState();
   }
   
   class _LocationScreenState extends State<LocationScreen> {
   Location location = new Location();
   
   late bool _serviceEnabled;
   late PermissionStatus _permissionGranted;
   late LocationData _locationData;
   
   
    Future<LocationData?>getLocation() async {
     _serviceEnabled = await location.serviceEnabled();
     if (!_serviceEnabled) {
       _serviceEnabled = await location.requestService();
       if (!_serviceEnabled) {
       return null;
       }
      }
   
      _permissionGranted = await location.hasPermission();
      if (_permissionGranted == PermissionStatus.denied) {
     _permissionGranted = await location.requestPermission();
      if (_permissionGranted != PermissionStatus.granted) {
       return null;
      }
    }
   
      _locationData = await location.getLocation();
      return _locationData;
   }
   

Answer 1

所以，

1. 第一个错误表明，当您尝试实现 HomeScreen 小部件时，没有提供名为 locationData 的必需参数，而要提供所需的参数，请遵循以下代码示例：

   HomeScreen(locationData: locationData)
   

   2. 第二个错误表明您正在尝试使用尚未定义的变量。在您尝试实现 HomeScreen 小部件的页面中，您应该定义一个名为 locationData 的变量，给它一个值，然后尝试使用 HomeScreen 小部件。例如：

   class LocationScreen extends StatefulWidget {
     const LocationScreen({Key? key}) : super(key: key);
   
   
     @override
     State<LocationScreen> createState() => _LocationScreenState();
   
   }
   
   class _LocationScreenState extends State<LocationScreen> {
   
     LocationData locationData;
   
     @override
     Widget build(BuildContext context) {
       //in case that you use the HomeScreen as a widget
       return locationData == null ? Container() : HomeScreen(locationData: locationData);
       //in case that you use the HomeScreen as Screen
       return Container();
     }
   
     void getLocationData() async{
       //in case that you use the HomeScreen as a widget
       //this function will change the state after the locationData have been filled
       locationData = await getLocation();
       setState(() {
       });
     }
   
     void navigateToHomeScreen() async{
       //in case that you use the HomeScreen as a widget
       //this function will change the state after the locationData have been filled
       locationData = await getLocation();
       Navigator.push(context, MaterialPageRoute(
           builder: (context) => HomeScreen(locationData: locationData);
       ));
     }
   
     Future<LocationData?> getLocation() async {
       _serviceEnabled = await location.serviceEnabled();
       if (!_serviceEnabled) {
         _serviceEnabled = await location.requestService();
         if (!_serviceEnabled) {
           return null;
         }
       }
   
       _permissionGranted = await location.hasPermission();
       if (_permissionGranted == PermissionStatus.denied) {
         _permissionGranted = await location.requestPermission();
         if (_permissionGranted != PermissionStatus.granted) {
           return null;
         }
       }
   
       _locationData = await location.getLocation();
       return _locationData;
     }
   }
   

   3. 第三个错误说不要在 HomeScreen 类中使用任何位置参数，因为您使用命名参数，如果您按照我的代码进行操作，它也会得到修复

   希望我有所帮助， 享受扑腾

Answer 2

在 HomeScreen 上，替换这行代码：

HomeScreen({required this.locationData,});

和

HomeScreen(this.locationData);

这应该清除 main.dart 上的错误