DropdownButtonFormField is not resetting first time - flutter

Question

I want to reset DropdownButtonFormField. I mange to reset it by setting it's value null and using globalkey as following code.
Here, problem is that i need to click twice to reset it.
Note: I know using DropdownButton, we can reset more easily but my question is why DropdownButtonFormField is not resetting when i click first time.
After Update:
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatefulWidget {
#override
MyAppState createState() => MyAppState();
}
class MyAppState extends State<MyApp> {
String abc;
FocusNode _node = FocusNode();
GlobalKey<FormState> _key = GlobalKey<FormState>();
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
body: Form(
key: _key,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Focus(
focusNode: _node,
onFocusChange: (bool focus) {
setState(() {});
},
child: Listener(
onPointerDown: (_) {
FocusScope.of(context).requestFocus(_node);
},
child: DropdownButtonFormField(
hint: Text('select value'),
value: abc,
items: <String>['A', 'B', 'C', 'D'].map((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
onChanged: (String newValue) {
setState(() {
abc = newValue;
});
},
),
),
),
Text("value is $abc"),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: () {
setState(() {
abc = null;
_key.currentState.reset();
});
},
tooltip: 'Reset',
child: Icon(Icons.clear),
)),
);
}
}

Answer 1

you may need to make manual Focus
you need to give the global key to form as well
FocusNode _node = FocusNode();
...
Focus(
focusNode: _node,
onFocusChange: (bool focus) {
setState(() {});
},
child: Listener(
onPointerDown: (_) {
FocusScope.of(context).requestFocus(_node);
},
child: DropdownButtonFormField(
iconSize: 50,
onChanged: (s) {
setState(() {
abc = s;
});
},
hint: Text(
'Select Text',
),
items: [
DropdownMenuItem(value: '1', child: Text('A')),
DropdownMenuItem(value: '2', child: Text('B')),
DropdownMenuItem(value: '3', child: Text('C')),
DropdownMenuItem(value: '4', child: Text('D')),
],
),
),
),
...
FloatingActionButton(
onPressed: () {
setState(() {
print("hello");
abc = null;
_key.currentState.reset();
});
// _flyIronMan();
},
child: Icon(Icons.add),
),