通过颤动创建集合的问题

Question

用户类别

class User {
    final String uid;
    final String username;
    final String email;
    final String photoUrl;
    final String displayName;
    final String bio;


User({
  this.uid,
  this.username,
  this.email,
  this.photoUrl,
  this.displayName,
  this.bio,
});

  factory User.fromDocument(DocumentSnapshot doc) {
    return User(
      uid: doc['uid'],
      email: doc['email'],
      photoUrl: doc['photoUrl'],
      displayName: doc['displayName'],
      bio: doc['bio']
    );
  }
}

在Firestore中创建新用户的工作原理是

：

createUserInFirestore() async {
  final FirebaseUser user = await FirebaseAuth.instance.currentUser();
   DocumentSnapshot doc = await usersRef.document(user.uid).get();

  if(!doc.exists) {
      final username = await Navigator.push(context, MaterialPageRoute(builder: (context) => CreateAccount(),));

     usersRef.document(user.uid).setData({
        "uid" : user.uid,
        "username" : username,
        "photoUrl" : user.photoUrl,
        "email" : user.email,
        "displayName" : username,
        "bio" : "",
        "timestamp" : timestamp

      });

      doc = await usersRef.document(user.uid).get();
    }

    currentUser = User.fromDocument(doc);

}

但是，无论出于何种原因都无法创建帖子-在出现空错误时调用ID：

createPostInFireStore({String mediaUrl, String description, String location}) async {
    postsRef.document(widget.currentUser.uid).collection("userPosts").document(postId).setData({
        "postId" : postId,
        "ownerId" : widget.currentUser.uid,
        "username": widget.currentUser.uid,
        "mediaUrl" : mediaUrl,
        "description" : description,
        "location" : location,
        "timestamp" : timestamp,
        "likes" : {},
      });
    }

  handleSubmit() async {
    setState(() {
      isUploading = true;
  });
  await compressImage();
  String mediaUrl = await uploadImage(file);
  createPostInFireStore(
    mediaUrl: mediaUrl,
    location: locationController.text,
    description: captionController.text
  );
  captionController.clear();
  locationController.clear();
  }

我的问题是，当用户要发布图像时，它不会创建posts集合。它将图像存储在存储器中，但不创建集合。