如何将图像上传到 Firebase 存储并获取 DownloadUrl Flutter

Question

我试图让这个应用程序学习在 Firebase 中使用的方法，现在，我正在使用 Cloud Firestore + Storage，但我收到了这个错误：

Exception has occurred.
FirebaseException ([firebase_storage/object-not-found] No object exists at the desired reference.)

我是 firebase 上的新人，所以我不知道该怎么办...还有很多更新和更改，其他帖子中的一些回复已被弃用...

  Future<void> uploadPic(File foto) async {
    final Reference postImageRef = FirebaseStorage.instance.ref().child('Post Images');
    var timeKey = DateTime.now();

    await postImageRef.child(timeKey.toString() + "jpg").putFile(foto)
    .whenComplete(() async { //IM GETTING THE ERROR HERE

    await postImageRef.getDownloadURL().then((value) { //IM GETTING THE ERROR HERE
        posts.imageUrl = value;
      });
    });
  return posts.imageUrl;
  }

这里是“保存”按钮的提交

  void _submit() async {
    if (!formKey.currentState.validate()) return null;
    formKey.currentState.save();

    uploadPic(foto);
    subirPost(posts);
    print(posts.datetime);
    mostrarToast('Producto guardado');
  }

Answer 1

这里的错误是你使用这种方法没有等待下载的图片链接返回给你：

注意：如果要同时上传和写入，必须等待提升完成后再写入。

1- 首先，创建一个包含 Firebase 中所有相关服务的外部 文件，假设其名称为 Api，并在其中添加此方法：

static Future<dynamic> postFile(
      {@required File imageFile, @required String folderPath}) async {
    String fileName = DateTime.now().millisecondsSinceEpoch.toString();

    Reference reference =
    FirebaseStorage.instance.ref().child(folderPath).child(fileName);

    TaskSnapshot storageTaskSnapshot =await reference.putFile(imageFile);

    print(storageTaskSnapshot.ref.getDownloadURL());

    var dowUrl = await storageTaskSnapshot.ref.getDownloadURL();


    return  dowUrl;
  }

2- 上传图片时，此方法会返回下载图片到 Firebase 的链接，并将其存储在对象中，如下所述：

 String imgUrl = await Api.postFile(
        imageFile: image,
        folderPath: 'image');

    if (imgUrl != null) {

      posts.imageUrl = imgUrl;

      ///Type here the command that will write to the firestore
    }

Answer 2

查看此工作代码 需要一个uuid包：https://pub.dev/packages?q=uuid

File _image;
final pickedFile = await ImagePicker()
    .getImage(source: ImageSource.camera, imageQuality: 80);
final String filePath = pickedFile != null ? pickedFile.path : '';
if (filePath.isNotEmpty) {
  _image = File(filePath);
  if (_image != null) {
    if (_image != null) {
      final Reference sref = storageReference
          .child('chat_multimedia/images/')
          .child(uuid.v4());

      final UploadTask storageUploadTask = sref.putFile(
        _image,
        SettableMetadata(
          contentType: mime(basename(_image.path)),
        ),
      );
      if (storageUploadTask.snapshot.state == TaskState.success) {
        final String url = await sref.getDownloadURL();
        print('The download URL is ' + url);
      } else if (storageUploadTask.snapshot.state == TaskState.running) {
        storageUploadTask.snapshotEvents.listen((event) {
          percentage = 100 *
              (event.bytesTransferred.toDouble() /
                  event.totalBytes.toDouble());
          print('THe percentage ' + percentage.toString());
        });
      } else {
        print('Enter A valid Image');
      }

      await storageUploadTask.whenComplete(() async {
        final String downloadUrl = await sref.getDownloadURL();
      });
    }
  }
 }