flutter - Flutter异步/等待在两个Firebase功能之间不起作用

Question

我正在尝试调用仅在另一个函数在Firebase Storage中返回文件的url但异步等待不起作用且无论如何都调用第二个函数而第二个函数仍未调用时才必须持久化对象的Cloud Firestore函数完成!!!

      await schoolProfileProvider.uploadSchoolProfileAvatar(data).then( (data) {
          schoolProfileProvider.addSchoolProfile(data);
        });
        print('PROFILE ADDED');

Future<SchoolProfileData> uploadSchoolProfileAvatar(SchoolProfileData data) async {
    List<File> avatars = [];
    data.childrenDetails.forEach((child) {
      avatars.add(File(child.childImage));
    });
    try {
       await _api.uploadFilesToStorage(avatars, 'image', 'png').then((urls) {
        for (var i = 0; i < urls.length; i++) {
          data.childrenDetails[i].childImage = urls[i];
          print('ADD ' + data.childrenDetails[i].childImage);
        }
      });
    } on Exception catch (e) {
      print(e.toString());
    }
    return data;
  }

  T cast<T>(x) => x is T ? x : null;
  Future<List<String>> uploadFilesToStorage(List<File> files, String type, String extension) async {
    final urls = <Future<String>>[];
    files.forEach((file) async {
      StorageReference storageRef = storage.ref().child(file.path);
      final StorageTaskSnapshot downloadUrl =
      (await storageRef
          .putFile(file, StorageMetadata(contentType: type + '/' + extension))
          .onComplete);
       await downloadUrl.ref.getDownloadURL().then((url) {
        urls.add(cast<Future<String>>(url));
        print('URL for file ${file.path} = ${url.toString()}');
      });
    });
    print ('urls returned');
    return Future.wait(urls);
  }

  Future addSchoolProfile(SchoolProfileData data) async{
    var result;
    try {
      result = await _api.addDocument(data.toJson());
    } on Exception catch(e) {
      print (e.toString());
    }
    return result;
  }

Answer 1

我设法通过减少嵌套函数并使等待的downloadUrl.ref.getDownloadURL()作为被调用者函数中返回的最后一条指令，完成了 uploadFilesToStorage 之后，使事情正常运行并执行 addSchoolProfile 。
请找到对谁感兴趣的代码:

call 者:

  schoolProfileProvider.addSchoolProfileAndUploadAvatar(data);

  Future addSchoolProfileAndUploadAvatar(SchoolProfileData data) async {
    List<File> avatars = [];
    data.childrenDetails.forEach((child) {
      avatars.add(File(child.childImage));
    });
    try {
         for (int i=0;i<avatars.length;i++){
           await _api.uploadFileToStorageAndGetUrl(avatars[i], 'image', 'png').then((url) {
             print('URL for file ${avatars[i].path} = ${url.toString()}');
             data.childrenDetails[i].childImage = url;
             print('ADD ' + data.childrenDetails[i].childImage);
           });
         }
         _api.addDocument(data.toJson()) ; // Add document in Google Firebase after setting the avatar url
    } on Exception catch (e) {
      print(e.toString());
    }
  }

被叫方:

Future <String>  uploadFileToStorageAndGetUrl(File file,String type, String extension) async{
    StorageReference storageRef = storage.ref().child(file.path);
    final StorageTaskSnapshot downloadUrl =
    (await storageRef
            .putFile(file, StorageMetadata(contentType: type + '/' + extension))
    .onComplete);
    return await downloadUrl.ref.getDownloadURL(); // return the url of the file in Google Storage
  }