title: Form data disappears on scroll Flutter
body: <p>I have implemented a form with a few TextFormFields. When i scroll the form the TextFormFields that are out of the view loses entered data. There is a similar question already posted <a href="https://stackoverflow.com/questions/45240734/flutter-form-data-disappears-when-i-scroll">here</a>. I have to no idea how to use a TextEditingController to save the state, since I am pretty new to Dart and Flutter. 
  I even tried using FormFieldStatePersistor following this <a href="https://github.com/rickbsgu/rbtile_formfield_demo" rel="nofollow noreferrer">github repo</a>. That also didn't work.  Any ideas on how to solve the issue? </p>