我在从Image.file到我的应用中调用firebase时遇到问题。我尝试将其转换为字符串，但有很多事情，但无济于事。
这是我从firebase提取数据的方式：（图像是文件，所以我将其包装在文件中）
Future<void> fetchAndSetCars() async {
const url = 'https://mylink.firebaseio.com/cars.json';
try {
final response = await http.get(url);
final extractedData = json.decode(response.body) as Map<String, dynamic>;
final List<AddCar> loadedCars = [];
extractedData.forEach((carId, carData) {
loadedCars.add(AddCar(
// other data
image: File(carData['image']),
));
});
_cars = loadedCars;
notifyListeners();
} catch (error) {
throw (error);
}
}
这是传递给firebase的数据：（我转换了Image.toString（），这是将文件传递给firebase以进行调用的错误方法吗？）
void addCar(AddCar car) {
const url = 'https://mylink.firebaseio.com/cars.json';
http.post(
url,
body: json.encode({
// other data
'image': car.image.toString(),
}),
);
final newCar = AddCar(
// other data
image: car.image,
);
_cars.insert(0, newCar);
notifyListeners();
}
以下是应该使用Image.file显示图像的方式：
child: Image.file(
image,
fit: BoxFit.fill,
),
最后使用ImagePicker从图库中选择file Image：
String img;
static Future<String> fileToB64(File f) async {
List<int> imageBytes = f.readAsBytesSync();
return base64Encode(
imageBytes,
);
}
Future<void> _takePicture() async {
final imageFile = await ImagePicker.pickImage(
source: ImageSource.gallery,
);
setState(() {
data.image = imageFile;
});
fileToB64(imageFile).then((d) {
setState(() {
img = d; //base64Decode(d);
});
});
}
// the button in my code
child: FlatButton(
child: Text(AppLocalizations.of(context).createAddImages),
onPressed: _takePicture,
),
这是堆栈跟踪：
Restarted application in 3,377ms.
E/flutter (12041): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The method 'forEach' was called on null.
E/flutter (12041): Receiver: null
E/flutter (12041): Tried calling: forEach(Closure: (String, dynamic) => Null)
E/flutter (12041): #0 Mobiles.fetchAndSetMobiles
package:flutter_app/providers/mobile_provider.dart:180
E/flutter (12041): <asynchronous suspension>
E/flutter (12041): #1 _MobilesAreaState.initState.<anonymous closure>
package:flutter_app/home_parts/mobiles_area.dart:17
E/flutter (12041): #2 _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter (12041): #3 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter (12041): #4 _FutureListener.handleValue (dart:async/future_impl.dart:137:18)
E/flutter (12041): #5 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:678:45)
E/flutter (12041): #6 Future._propagateToListeners (dart:async/future_impl.dart:707:32)
E/flutter (12041): #7 Future._complete (dart:async/future_impl.dart:512:7)
E/flutter (12041): #8 new Future.delayed.<anonymous closure> (dart:async/future.dart:313:16)
E/flutter (12041): #9 _rootRun (dart:async/zone.dart:1120:38)
E/flutter (12041): #10 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter (12041): #11 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
E/flutter (12041): #12 _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:963:23)
E/flutter (12041): #13 _rootRun (dart:async/zone.dart:1124:13)
E/flutter (12041): #14 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter (12041): #15 _CustomZone.bindCallback.<anonymous closure> (dart:async/zone.dart:947:23)
E/flutter (12041): #16 Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:21:15)
E/flutter (12041): #17 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
E/flutter (12041): #18 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
E/flutter (12041): #19 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:172:12)
问题在于，获取图像或将图像传递给Firebase的方式比肯定的多，但我尝试了无数种方法，但似乎没有任何效果。
答案 0 :(得分：0)
确保您使用的是firebase storage，而不是用于图像的Firebase数据库。参见此SO answer。一旦有了实例Firebase存储和存储引用，它应该像在该引用上调用方法一样简单。
编辑：这是一些未经测试的代码，显示了一种方法。
import 'package:approachbuilder/models/profile.dart';
import 'package:cached_network_image/cached_network_image.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:flutter/material.dart';
import 'package:image_picker/image_picker.dart';
import 'package:path/path.dart' as path;
final FirebaseStorage firebaseStorage = FirebaseStorage();
final StorageReference storageReference = firebaseStorage.ref();
class UserProfileImage extends StatelessWidget {
UserProfileImage(this.userDocument);
/// The current user's profile document in firebase
/// gotten through Firestore.instance.collection('users).document(userId);
final DocumentReference userDocument;
@override
Widget build(BuildContext context) {
return StreamBuilder<Profile>(
// Unnecessary step, maps the raw profile into a class intance
// that uses a JsonSerializable and FunctionalData model
stream: userDocument
.snapshots()
.map((snapshot) => Profile.fromJson(snapshot.data)),
builder: (context, snapshot) {
if (!snapshot.hasData) return CircularProgressIndicator();
return GestureDetector(
onTap: () => _getAndSetImage(snapshot.data),
// Traditional NetworkImage doesn't handle errors that well
child: CachedNetworkImage(
imageUrl: snapshot.data.photoUrl,
placeholder: (context, url) => CircularProgressIndicator(),
errorWidget: (context, url, error) => Icon(Icons.error),
),
);
},
);
}
void _getAndSetImage(Profile profile) async {
final imageFile = await ImagePicker.pickImage(source: ImageSource.camera);
if (imageFile == null) return;
final baseImageFileName = path.basename(imageFile.path);
final imageRef = storageReference.child(baseImageFileName);
final uploadTask = imageRef.putFile(imageFile);
await uploadTask.onComplete.then((snapshot) async {
// File has been successfully added to firebase storage
final downloadUrl = await snapshot.ref.getDownloadURL();
// Remove previous photoUrl from fb storage if there is one
await deleteFirebaseResource(profile.photoUrl);
await userDocument.setData(
profile.copyWith(photoUrl: downloadUrl).toJson(),
);
});
}
Future<void> deleteFirebaseResource(String url) async {
StorageReference storageRef =
await firebaseStorage.getReferenceFromUrl(url);
if (storageRef == null) return;
await storageRef.delete();
}
}