Flutter - CupertinoPicker in an alert dialog - flutter

Question

I am stuck right now with the little app that I am trying to create.
The user when he will tap on an icon is supposed to get an alert dialog with 2 buttons (OK and Cancel), and in the body of the alert box, a Cupertino Picker. Below you will find the code. I am getting this error message.
Failed assertion: line 85 pos 15: 'children != null': is not true.
class Engage extends StatefulWidget {
Engage ({Key key}) : super(key:key);
#override
_EngageState createState() => _EngageState();
}
class _MyEngageState extends State<MyEngage> {
#override
Widget build(BuildContext context) {
return Container(
padding: const EdgeInsets.all(10.0),
decoration: BoxDecoration(
border: Border.all(color: Colors.grey[350])),
child: Column(
children: [
Padding(
padding: const EdgeInsets.all(3.0),
child: Container(
// margin: const EdgeInsets.all(30.0),
padding: const EdgeInsets.all(10.0),
decoration: BoxDecoration(
border: Border.all(color: Colors.grey[350])
),
child : Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
GestureDetector(
child: Column(
children: [
IconButton(
splashColor: Colors.lightGreenAccent,
icon : Image.asset('assets/icons/icon1',
height: iconHeighEngage,),
onPressed:(){
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text('TEST'),
content: Container(
height: 350,
child: Column(
children: <Widget>[
CupertinoPicker(),
FlatButton(
child: Text("OK"),
onPressed: () {
Navigator.pop(context);
},
)
],
),
));
});
},
),
Text('TEST')],
),
),

Answer 1

Give it a try to this!
Padding(
padding: const EdgeInsets.all(3.0),
child: Container(
// margin: const EdgeInsets.all(30.0),
padding: const EdgeInsets.all(10.0),
decoration: BoxDecoration(
border: Border.all(color: Colors.grey[350])),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
GestureDetector(
child: Column(
children: [
IconButton(
splashColor: Colors.lightGreenAccent,
icon: Icon(
Icons.add,
),
onPressed: () {
showDialog(
context: context,
builder: (BuildContext ctx) {
return AlertDialog(
title: Text('My Titile'),
content: Container(
height: 350,
width: 350.0,
child: Column(
children: <Widget>[
CupertinoPicker(
itemExtent: 200.0,
onSelectedItemChanged:
(int value) {
print("Test");
},
children: <Widget>[
FlatButton(
child: Container(
color:
Colors.orangeAccent,
width: 350.0,
height: 160.0,
child: Center(
child: Text(
"OK",
style: TextStyle(
fontSize: 20.0),
)),
),
onPressed: () {
Navigator.pop(context);
},
)
],
),
],
),
),
);
},
);
},
),
Text('TEST')
],
),
),
],
),
),
)
Note: The problem was, you weren't passing the parameters of CupertinoPicker()
EDIT :
First Initialize
int selected = 0;
and then:
Padding(
padding: const EdgeInsets.all(3.0),
child: Container(
padding: const EdgeInsets.all(10.0),
decoration:
BoxDecoration(border: Border.all(color: Colors.grey[350])),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
GestureDetector(
child: Column(
children: [
IconButton(
splashColor: Colors.lightGreenAccent,
icon: Icon(
Icons.add,
),
onPressed: () {
showDialog(
context: context,
builder: (BuildContext ctx) {
return StatefulBuilder(
builder: (context, setState) {
return AlertDialog(
backgroundColor: Colors.lightBlueAccent,
title: Text(
'My Dialog',
style: TextStyle(
color: Colors.white,
fontSize: 30.0,
fontWeight: FontWeight.bold,
),
),
content: Container(
height: 350.0,
width: 350.0,
child: Column(
children: <Widget>[
Expanded(
child: CupertinoPicker(
useMagnifier: true,
magnification: 1.5,
backgroundColor: Colors.white,
itemExtent: 40.0,
onSelectedItemChanged: (int index) {
print(selected);
setState(() {
selected = index;
});
print(selected);
},
children: <Widget>[
Text(
"Text 1",
style: TextStyle(
color: selected == 0
? Colors.blue
: Colors.black,
fontSize: 22.0),
),
Text(
"Text 2",
style: TextStyle(
color: selected == 1
? Colors.blue
: Colors.black,
fontSize: 22.0),
),
Text(
"Text 3",
style: TextStyle(
color: selected == 2
? Colors.blue
: Colors.black,
fontSize: 22.0),
),
],
),
)
],
),
),
);
},
);
},
);
},
),
Text('Add')
],
),
),
],
),
),
),
The code is tested and working pretty fine now!