Flutter , type ‘Null’ is not a subtype of type ‘String’

Posted by


type 'Null' is not a subtype of type 'String'The relevant error-causing widget was:


The reason for the error type ‘Null’ is not a subtype of type ‘String’ is that you are attempting to use a value that might be null as if it were a String no matter what. It appears that in your case, the _dropdownValue variable is the problem.

Although you initialised _dropdownValue to be ‘Select Council,’ you are using the?? operator when setting its value in initState. This means that if widget.registrationData[‘regcouncil’] is null, ‘Select Council’ will be used instead. You must make sure the value you assign to _dropdownValue is not null, though, as it is still a String and not String? (nullable String).

You can update _dropdownValue’s initialisation to be nullable (String?) and modify the initialisation in

late String? _dropdownValue;

Then, in initState, set _dropdownValue based on whether widget.registrationData['regcouncil'] is null or not:

_dropdownValue = widget.registrationData['regcouncil'] as String? ?? 'Select Council';

This ensures that _dropdownValue is always of type String?, which can handle null values, and defaults to 'Select Council' if the value is null.

Notify of
Inline Feedbacks
View all comments
Would love your thoughts, please comment.x