React-Native this.setState() is not working

Your Login components onUpdate method is probably called with an object that cannot be serialized. For example it could contain functions, or maybe circular references.

In your onUpdate method you should pick the stuff you are interested in from the val argument, and insert that into the state. Something like this:

this.setState({
userName: val.userName,
userId: val.userId
});

or whatever is included in the object that is sent to onUpdate.