Widget in Future - flutter

Question

I am trying to use a dialog widget which will get some info from future builder, when I build the dialog under onTap it works but code looks so weird in that way because I use that build more then once, so I want to make a dialog class then call it when I needed but I couldn't achieve that yet, is this possible? My related code samples are below;
Code in the screen that I tried to call dialog box(homepage.dart):
void showCast() {
showDialog<void>(
context: context,
builder: (context){
return CastDialog();
}
);
}
#override
Widget build(BuildContext context) {
return FutureBuilder<Payload>(
...
...
...
child: GestureDetector(
child: Image.network(
snapshot.data
.movieCast[index]
.image != null
? "http://image.tmdb.org/t/p/w185" +
snapshot.data
.movieCast[index]
.image
: "http://image.tmdb.org/t/p/original/zUqyn3aQXTzeP1n8yd8Udt1twYA.jpg",
fit: BoxFit.contain,),
onTap: () async {
List<dynamic> castVar;
http.Response responseC = await http.get("http://lunedor.pythonanywhere.com/query?castid=${snapshot.data.movieCast[index].castID}&language=${AppLocalizations.of(context).translate('lan_code')}").timeout(const Duration(seconds: 10));
Map<String, dynamic> castV = jsonDecode(responseC.body);
castVar = castV['moviecastimages'];
print(castVar);
String nameC = (snapshot.data.movieCast[index]).toString();
String _movieCast = (snapshot.data.movieCast[index]).toString();
String _url = (snapshot.data.movieCast[index].castID).toString();
return
showCast();
},
),
Code for dialog(dialogs.dart):
class CastDialog extends StatefulWidget{
#override
_CastDialogState createState() => _CastDialogState();
}
class _CastDialogState extends State<CastDialog> {
String nameC;
String _movieCast;
String _url;
List castVar;
void initState() {
super.initState();
}
#override
Widget build(BuildContext context) {
return SimpleDialog(
title:
Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
SizedBox(
width: 20,
height: 20,
child: GestureDetector(
onTap: () async{
http.Response responseB = await http.get("https://api.themoviedb.org/3/person/$_url?api_key=1b8cfaea32775f684a7baff93bb1a3fc&language=${AppLocalizations.of(context).translate('lan_code')}").timeout(const Duration(seconds: 10));
Map<String, dynamic> castCB = jsonDecode(responseB.body);
return showDialog(context: context,
builder: (context) {
return SimpleDialog(
title: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Text(nameC),
SizedBox(
width: 20,
height: 20,
child: GestureDetector(
onTap: (){ Navigator.pop(context);},
child: Icon(Icons.close)),
),
],
),
children: <Widget>[
Divider(
color: Colors.black.withOpacity(0.5),
height: 5,
thickness: 3,
),
Wrap(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
child: Text(castCB['biography'], style: TextStyle(fontSize: 14),),
),
),
],
),],
);
});
},
child: Icon(Icons.info)),
),
Text(_movieCast),
SizedBox(
width: 20,
height: 20,
child: GestureDetector(
onTap: (){ Navigator.pop(context);},
child: Icon(Icons.close)),
),
],
),
shape: RoundedRectangleBorder(borderRadius: new BorderRadius.circular(15.0)),
children: <Widget>[
Divider(
color: Colors.black.withOpacity(0.5),
height: 5,
thickness: 3,
),
Material(
child: Container(
width: 400,
height: 600,
child: new GridView.builder(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 2,
childAspectRatio: 1.5 /
2.5,
),
itemCount: castVar.length,
itemBuilder: (context, index) {
return Column(
children: <
Widget>[
SizedBox(
height: 220,
child: Stack(
children: <Widget>[
Image.network(castVar[index]['poster'] != null ? "http://image.tmdb.org/t/p/w185" + castVar[index]['poster']
: "https://i.hizliresim.com/bbn0VB.jpg", fit: BoxFit.contain),
Container(
width: MediaQuery
.of(context)
.size
.width,
height: 220,
alignment: Alignment.bottomLeft,
padding: EdgeInsets.only(bottom: 5.0),
margin: const EdgeInsets.only(
left: 5.0),
child: new CircularPercentIndicator(
radius: 40.0,
lineWidth: 5.0,
percent: double.tryParse(
castVar[index]['vote'])/10,
center: Stack(
children: <Widget>[
Text(
castVar[index]['vote'],
style: TextStyle(
foreground: Paint()
..style = PaintingStyle.stroke
..strokeWidth = 3
..color = Colors.black,
),
),
new Text(castVar[index]['vote'],
style: TextStyle(
fontWeight: FontWeight.bold,
color: Colors.amber,),),
],
),
progressColor: Colors.amber,
)
),],
),
),
Text(castVar[index]['title'], maxLines: 1,
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 14.0,
fontWeight: FontWeight.bold)
),
Text("(" + castVar[index]['year'] + ")", maxLines: 1,
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 14.0,
fontWeight: FontWeight.bold,),
)
],
);
}),
),
),
],
);
}
}