Duplicate GlobalKey detected in Widget Tree or Multiple Widgets used the same GlobalKey - flutter

Question

I've tried to create form to input something from textfield to database using rest service, it worked just fine from the first try, but it got error the next time I tried, the error said there was something wrong with the GlobalkKey, so it's maybe around here.
class _DeliveryRecieverState extends State<DeliveryReciever> {
List datas;
File imagePath;
bool validasi = false;
String namaPenerima;
final _keyFormReceiver = GlobalKey<FormState>();
#override
Widget build(BuildContext context) {
datas = this.datas;
print(datas);
return DefaultTabController(
length: 1,
child: Scaffold(
backgroundColor: Colors.white,
appBar: AppBar(
bottom: TabBar(
tabs: <Widget>[
Tab(
icon: Icon(Icons.local_shipping),
text: "Bukti Delivery",
),
],
),
elevation: 0.1,
// backgroundColor: Colors.cyan[800],
flexibleSpace: Container(
decoration: BoxDecoration(
gradient: LinearGradient(
colors: [Color(0xFF17ead9), Color(0xFF6078ea)]),
),
),
title: Text(
"Delivery",
style: TextStyle(
fontFamily: "Popins-Bold",
fontSize: ScreenUtil.getInstance().setSp(46),
letterSpacing: .6,
fontWeight: FontWeight.bold,
),
),
actions: <Widget>[
],
),
body: TabBarView(
children: <Widget>[
SingleChildScrollView(
child: Padding(
padding: EdgeInsets.only(
left: 15.0, right: 15.0, top: 15.0, bottom: 15.0),
child: Column(
children: <Widget>[
Container(
width: double.infinity,
height: ScreenUtil.getInstance().setHeight(470),
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(8.0),
boxShadow: [
BoxShadow(
color: Colors.black12,
offset: Offset(0.0, 15.0),
blurRadius: 15.0),
BoxShadow(
color: Colors.black12,
offset: Offset(0.0, -10.0),
blurRadius: 10.0)
]),
child: Padding(
padding: EdgeInsets.only(
left: 16.0, right: 16.0, top: 16.0),
child: Form(
key: _keyFormReceiver,
autovalidate: validasi,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
"Nama Penerima",
style: TextStyle(
fontSize:
ScreenUtil.getInstance().setSp(30),
fontFamily: "Poppins-Bold",
letterSpacing: .6),
),
SizedBox(
height:
ScreenUtil.getInstance().setHeight(30),
),
TextFormField(
validator: validasiReceivername,
onSaved: (String nama) {
namaPenerima = nama;
},
decoration: InputDecoration(
hintText: "Nama Penerima",
hintStyle: TextStyle(
color: Colors.grey,
fontSize: 12.0)),
),
SizedBox(
height:
ScreenUtil.getInstance().setHeight(50),
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(10.0),
child: RaisedButton(
elevation: 7.0,
color: Colors.green,
padding: EdgeInsets.all(20.0),
child: Text("LANJUT"),
textColor: Colors.white,
shape: RoundedRectangleBorder(
borderRadius:
BorderRadius.circular(10)),
onPressed: () {
parseData();
},
),
),
],
),
],
),
)),
),
],
),
),
),
],
),
bottomNavigationBar: Container(
height: 55.0,
child: BottomAppBar(
child: Container(
decoration: BoxDecoration(
gradient: LinearGradient(
colors: [Color(0xFF17ead9), Color(0xFF6078ea)]),
),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
IconButton(
icon: Icon(Icons.home, color: Colors.white),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => halamanUtama()),
);
},
),
IconButton(
icon: Icon(Icons.nature_people, color: Colors.white),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => UpcomingDelivery()),
);
},
),
IconButton(
icon: Icon(Icons.local_shipping, color: Colors.white),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => ListDelivery()),
);
},
),
],
),
),
),
),
));
}
String validasiReceivername(String value) {
if (value.length == 0) {
//Toast.show("Password more than 4 ", context,duration: Toast.LENGTH_SHORT, gravity: Toast.CENTER);
return "Nama penerima tidak boleh kosong.";
} else {
return null;
}
}
void parseData() async {
if (_keyFormReceiver.currentState.validate()) {
_keyFormReceiver.currentState.save();
_keyFormReceiver.currentState.reset();
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => CustomerSignatureProof(
created_name: widget.created_name,
wmsorders_id: widget.wmsorders_id,
imagePath: widget.imagePath,
imageName: widget.imageName,
receiverName: namaPenerima,
upcoming_id: widget.upcoming_id,
upcoming_sku: widget.upcoming_sku,
upcoming_sak: widget.upcoming_sak,
upcoming_qty: widget.upcoming_qty,
upcoming_shipstatid: widget.upcoming_shipstatid,
upcoming_picname: widget.upcoming_picname,
upcoming_pictelp: widget.upcoming_pictelp,
upcoming_ordermultipleid: widget.upcoming_ordermultipleid,
upcoming_orderdetid: widget.upcoming_orderdetid,
upcoming_coordinatorid: widget.upcoming_coordinatorid,
upcoming_shipmentid: widget.upcoming_shipmentid)));
}
}
}
Here is the error in terminal,
Have anybody face the same probles as me, please give your guidance..