Flutter How to print selected value on textfield when keyboard is hide

hellow thank you in advance can you help me....! i made dropbox under the textfield..and in that case...i dont want keyboard...! but when i selecte value from my items then that value is not printed on my textfield...! let me explain you as live... if you are a existing custmor the value is shown on textfield and when you select value MALE FEMALE is not going to change.....! if i remove the onTap() {} from my textfield its going to change...! what should i do now i stuck here since 2,3 days
look at my code

@override
Widget build(BuildContext context) {
return Scaffold(
body: (_isLoading) ? Center(child: CircularProgressIndicator()) :
FutureBuilder<UserUpdate>(
future: _futureProfileupdate,
builder: (context, snapshot) {
if (snapshot.hasData) {

TextEditingController _textEditingControllerGender = TextEditingController(text:
snapshot.data.gender);
var items = ["MALE" , "FEMALE"];

return Form(
key: _formKey,
child: Stack(
children: <Widget>[
SingleChildScrollView(
reverse: true,
child: new Column(
children: <Widget>[

Padding(
padding: const EdgeInsets.only(top: 10,left: 30,right: 30),
child: SizedBox(
height: 65,
child: TextFormField(
onTap: (){
FocusScope.of(context).requestFocus(new FocusNode());
}, // if i remove this iteam is going to print on tetxfiled
focusNode: FocusNode(canRequestFocus: false),
textInputAction: TextInputAction.next,
controller: _textEditingControllerGender,
decoration: InputDecoration(
enabledBorder: OutlineInputBorder(
borderRadius: BorderRadius.circular(5.0),
borderSide: BorderSide(
color: Color(0x3df58634)
)
),
labelText: "GENDER",
labelStyle: GoogleFonts.nunito(
color: const Color(0xfff58634)),
hintText: "GENDER",
hintStyle: GoogleFonts.nunito(
color: const Color(0xfff58634)),
focusedBorder: OutlineInputBorder(
borderRadius: BorderRadius.circular(
5.0),
borderSide: BorderSide(
color: const Color(0x3df58634),
)
),
suffixIcon: PopupMenuButton<String>(
icon: const Icon(Icons.arrow_drop_down),
onSelected: (String value) {
_textEditingControllerGender.text = value;
},
itemBuilder: (BuildContext context) {
return items
.map<PopupMenuItem<String>>((String value) {
return new PopupMenuItem(
child: new Text(value), value: value);
}).toList();
},
),
),
onSaved: (String value) {
_Gender = value;
},

),
),
),

Padding(
padding: EdgeInsets.only(top: 10.0,left: 230,right: 30),
child: SizedBox(
width: 140,
height: 45,
child: RaisedButton(
onPressed: () {
if (!_formKey.currentState.validate()) {
return;
}
setState(() {
_isLoading = true;
});
Profile(

_textEditingControllerGender.text,

);
},
here is my json data.... plz help me i am stuck here since 2,3 days UserUpdate userUpdateFromJson(String str) => UserUpdate.fromJson(json.decode(str));

String userUpdateToJson(UserUpdate data) => json.encode(data.toJson());

class UserUpdate {
UserUpdate({
this.successCode,
this.successMessage,
this.firstName,
this.lastName,
this.email,
this.gender, //i want thiis default to my textfiled and change when i select new
this.birthDate,
this.birthMonth,
this.anniversaryDate,
this.profilePicture,
});

String successCode;
String successMessage;
String firstName;
String lastName;
String email;
dynamic gender;
String birthDate;
String birthMonth;
String anniversaryDate;
String profilePicture;

factory UserUpdate.fromJson(Map<String, dynamic> json) => UserUpdate(
successCode: json["SuccessCode"],
successMessage: json["SuccessMessage"],
firstName: json["FirstName"],
lastName: json["LastName"],
email: json["Email"],
gender: json["Gender"],
birthDate: json["BirthDate"],
birthMonth: json["BirthMonth"],
anniversaryDate: json["AnniversaryDate"],
profilePicture: json["ProfilePicture"],
);

Map<String, dynamic> toJson() => {
"SuccessCode": successCode,
"SuccessMessage": successMessage,
"FirstName": firstName,
"LastName": lastName,
"Email": email,
"Gender": gender,
"BirthDate": birthDate,
"BirthMonth": birthMonth,
"AnniversaryDate": anniversaryDate,
"ProfilePicture": profilePicture,
};
}