Flutter TextFormField reloads current screen when focused

The problem is that the controller of the TextFormField is rebuild when you click on the field, and that's the reason of your issue.

So to solve that, did you try to create a Statefull widget and then creating a TextEditingController in the State of this widget and passing it as an argument to the TextFormField ?

I had the same Problem. this was my code

class MainPage extends StatefulWidget {
  @override
  _MainPageState createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  Model model = Model();

  @override
  Widget build(BuildContext context) {
  GlobalKey<FormState> _formKey = GlobalKey<FormState>();
    var mediaWidth = MediaQuery.of(context).size.width / 2.0;
    return Scaffold(
...

and I solved this problem by declaring the _formKey outside of build method. and this worked for me.

class MainPage extends StatefulWidget {
  @override
  _MainPageState createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  Model model = Model();
  GlobalKey<FormState> _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    var mediaWidth = MediaQuery.of(context).size.width / 2.0;
    return Scaffold(
...

hope it will help you