Flutter textformfield initialValue double passed in shows null

hi,

I have latitude and longitude as doubles in my form, the TextFormField only takes strings, when I try to set the initialValue as the double latitude value, it outputs null. Is there a way around this?

new TextFormField(
                              initialValue: "${this.latitudeData}".toString(),
                              keyboardType: TextInputType.text,
                              onSaved: (input) =>
                                  findsRequestModel.latitude = latitudeData,
                              decoration: new InputDecoration(.....

Thanks