无法将Firebase存储映像的Url添加到实时数据库

Question

在这个应用程序中，我点击一张照片，要么是通过相机，要么是从图库上传，然后把它传递给一个提供商。我想将该映像上传到Firebase存储区，然后将其映像Url与其他字符串和double类型信息一起存储在一个实时数据库中。但我似乎不能这样做，因为数据似乎在图像url可以被处理之前就上传到了实时数据库中。图像仍然正确地上载在存储中。下面是我的Provider类的代码。

有关的方法有uploadPic（）和addPlace（）

import 'dart:io';
import 'dart:convert';
import 'package:path/path.dart' as Path;
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:firebase_storage/firebase_storage.dart';
import '../models/place.dart';

class MyPlaces with ChangeNotifier {

  List<Place> _places = [];

  List<Place> get places {
    return [..._places];
  }

  Future<void> fetchAndSetPlaces() async {
    const url = 'my firebase url';
    try {
      final response = await http.get(url);
      final extractedData = json.decode(response.body) as Map<String,dynamic>;
      final List<Place> loadedPlaces = [];
      extractedData.forEach((id, data) {
        loadedPlaces.add(Place(
          id: id,
          cropName: data['cropName'],
          imageUrl: data['imageUrl'],
          location: Location(
            latitude: data['latitude'],
            longitude: data['longitude'],
            //address: data['address'],
          ),
        ));
        _places = loadedPlaces;
        notifyListeners();
      });
    } catch(error) {
      throw error;
    }
  }

  Future<void> addPlace(String cropName, File image, Location loc) async {
    const url = 'my firebase url';
    String imageUrl;
    await uploadPic(image, imageUrl);
    try {
      final response = await http.post(url, body: json.encode({
        'cropName' : cropName,
        'imageUrl' : imageUrl,
        'latitude' : loc.latitude,
        'longitude' : loc.longitude,
      }));
      final newPlace = Place(
      id: json.decode(response.body)['name'],
      cropName: cropName,
      imageUrl: imageUrl,
      location: loc,
    );
      _places.add(newPlace);
      notifyListeners();
    } catch (error) {
      throw error;
    }


  }

  Place findPlaceById(String id) {
    return _places.firstWhere((place) => place.id == id);
  }

  Future uploadPic(pickedImage, imageUrl) async {
      StorageReference firebaseStorageRef = FirebaseStorage.instance.ref().child('chats/${Path.basename(pickedImage.path)}}');
      StorageUploadTask uploadTask = firebaseStorageRef.putFile(pickedImage);
      await uploadTask.onComplete;
      print("File uploaded!");
      firebaseStorageRef.getDownloadURL().then((fileUrl) {
        imageUrl = fileUrl;
      });
      notifyListeners();
  }

}

我正在submitForm（）方法中的表单页中调用addplace（）方法。

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import '../models/place.dart';
import '../providers/my_places.dart';
import '../widgets/image_input.dart';
import '../widgets/location_input.dart';
import '../widgets/custom_drawer.dart';
import '../screens/my_geo_tags_screen.dart';

class AddNewPlaceScreen extends StatefulWidget {

  static const routeName = '/add_new_place_screen';

  @override
  _AddNewPlaceScreenState createState() => _AddNewPlaceScreenState();
}

class _AddNewPlaceScreenState extends State<AddNewPlaceScreen> {

  Place currentPlace;

  final _cropNameController = TextEditingController();
  File _pickedImage;
  Location _pickedLocation;

  void selectImage(File image) {
    setState(() {
      _pickedImage = image;
    });
  }

  void selectLocation(double lat, double long) {
    _pickedLocation = Location(
      latitude: lat,
      longitude: long,
    );
  }



  void _submitForm() {
    if (_cropNameController.text == null || _pickedImage == null || _pickedLocation == null) {
      return;
    }
    Provider.of<MyPlaces>(context).addPlace(_cropNameController.text, _pickedImage, _pickedLocation);
    Navigator.of(context).pop();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Add new Geo Tag", style: Theme.of(context).textTheme.title),
        iconTheme: IconThemeData(color: Colors.amber),
      ),
      drawer: CustomDrawer(),
      body: SingleChildScrollView(
        child: Container(
          padding: EdgeInsets.all(20),
          child: Column(
            children: <Widget>[
              TextField(
                style: TextStyle(
                  color: Theme.of(context).primaryColor,
                ),
                decoration: InputDecoration(
                  border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(5),
                  ),
                  labelText: "Name of the crop",
                  labelStyle: TextStyle(
                    color: Theme.of(context).primaryColor,
                  ),
                ),
                controller: _cropNameController,
              ),
              SizedBox(height: 15),
              ImageInput(selectImage),
              SizedBox(height: 15),
              LocationInput(selectLocation),
            ],
          ),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        backgroundColor: Theme.of(context).accentColor,
        child: Icon(
          Icons.save,
          color: Theme.of(context).primaryColor,
        ),
        onPressed: () {
          _submitForm();
          Navigator.of(context).pushReplacementNamed(MyGeoTagsScreen.routeName);
        },
      ),
    );
  }
}

Answer 1

我认为您需要在future uploadpic中等待firebaseStorageRef.getDownloadURL（）.然后（（fileUrl）{。但是，我认为混合使用await和.then可能会导致问题。所以尝试删除.然后，只需执行以下语句imageUrl=await firebaseStorageRef.getDownloadURL（）；