Flutter Cloud Firestore Map<String, dynamic> error

I believe this is because the Map returned from Firebase is not a Map<String, dynamic> but instead Map<dynamic, dynamic>.

See https://github.com/flutter/flutter/issues/17417 for a related issue.

Use Map<String, dynamic>.from ( mapFromFirestore ). This creates a new Map<String, dynamic> from the contents of mapFromFirestore, throwing an error if it finds a key that isn't a String.

I too had this problem and fixed it with --

  Map<String, dynamic> var = {'item': 0, 'name': 'John'}  

instead of Map unspecified.

  Map var = {'item': 0, 'name': 'John'}