[flutter-chat-demo]setting2.dart

Future uploadFile() async {
    String fileName = id;
    StorageReference reference = FirebaseStorage.instance.ref().child(fileName);
    StorageUploadTask uploadTask = reference.putFile(avatarImageFile);
    StorageTaskSnapshot storageTaskSnapshot;
    uploadTask.onComplete.then((value) {
        if (value.error == null) {
            storageTaskSnapshot = value;
            storageTaskSnapshot.ref.getDownloadURL().then((downloadUrl) {
                photoUrl = downloadUrl;
                Firestore.instance
                    .collection('users')
                    .document(id)
                    .updateData({
                        'nickname': nickname,
                        'aboutMe': aboutMe,
                        'photoUrl': photoUrl
                    }).then((data) async {
                        await prefs.setString('photoUrl', photoUrl);
                        setState(() {
                            isLoading = false;
                        });
                        Fluttertoast.showToast(msg: "Upload success");
                    }).catchError((err) {
                        setState(() {
                            isLoading = false;
                        });
                        Fluttertoast.showToast(msg: err.toString());
                    });
            }, onError: (err) {
                setState(() {
                    isLoading = false;
                });
                Fluttertoast.showToast(msg: 'This file is not an image');
            });
        } else {
            setState(() {
                isLoading = false;
            });
            Fluttertoast.showToast(msg: 'This file is not an image');
        }
    }, onError: (err) {
        setState(() {
            isLoading = false;
        });
        Fluttertoast.showToast(msg: err.toString());
    });
}