PageView error after exit and coming back

Question

so i change my statefull PageView Widget getter to _globalState so i can update the state from another widget but after i exit from the PageView to Home and comeback again to PageView it results error.

from this

class SurveyFormPage extends StatefulWidget {
      @override
      _SurveyFormPageState createState() => _SurveyFormPageState();
    }

to this

    _SurveyFormPageState _globalState = new _SurveyFormPageState();
        
        class SurveyFormPage extends StatefulWidget {   @override  
        _SurveyFormPageState createState() => _globalState; 
}

error results