Flutter The method '[]' was called on null error

Question

I have a Flutter app with Firebase backend. I am using email and google sign in method. When user sign in for the first time using google sign in method, this wierd error pops up just for a second. (When user register using email/pswrd, this doesnt appear)

The following NoSuchMethodError was thrown building StreamBuilder(dirty, state: _StreamBuilderBaseState>#e1ffb): The method '[]' was called on null. Receiver: null Tried calling:

Here is my code on github: https://github.com/TenPetr/fridgy (this error is probably caused from lib/pages/home.dart file)

Thanks for your answers!

Answer 1

This happens because when you Stream is in its loading state, the way to solve this is to use the ConnectionState of the stream and show either a ProgressBar or a empty container.

//Data Logic
Stream<QuerySnapshot> snapshot =  Firestore.instance.collection("collection_name").snapshots();

//Ui Logic
StreamBuilder(
  stream: snapshot,
  builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
    if(snapshot.connectionState == ConnectionState.active) {
      //Further Logic
      return Text('It works');
    } else {
      return CircularProgressIndicator();
    }
  },
);

Answer 2

I found that the error is timing due to the user @Preet Parekh. And I solve this issue by removing method that was responsible for determine if user is logged for the first time or not. Instead of this, I used propery on AuthResult - result.additionalUserInfo.isNewUser

https://firebase.google.com/docs/reference/android/com/google/firebase/auth/AdditionalUserInfo

Thanks for your help.