setState() on showDialog() from initState() is not changing the state. Flutter - flutter

Question

I have created a dialog with StatefulBuilder. Setstate works perfectly within the StatefulBuilder. But I want to change that state from initstate too. But the set state from initstate is not called.
My code:
#override
void initState() {
super.initState();
rest_controller = AnimationController(
vsync: this,
duration: Duration(seconds: 15),
);
rest_controller.addListener(() {
if (rest_controller.isAnimating) {
setState(() {
print("rp"+rest_progress.toString());
rest_progress = rest_controller.value;
});
} else {
setState(() {
print("rp2"+rest_progress.toString());
rest_progress = 1.0;
rest_isPlaying = false;
});
}
});
}
Dialog open function:
showDataAlert() {
showDialog(
context: context,
builder: (context) {
return StatefulBuilder(
builder: (context, setState) {
return AlertDialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(
Radius.circular(
20.0,
),
),
),
backgroundColor: kMainColor,
contentPadding: EdgeInsets.only(
top: 10.0,
),
title: Text(
"Take Rest",
style: TextStyle(fontSize: 24.0, color: kTextColor),
),
content:
Center(
child: Column(
children: [
SizedBox(
height: 10,
),
Expanded(
child: Stack(
alignment: Alignment.center,
children: [
SizedBox(
width: 260,
height: 260,
child: CircularProgressIndicator(
backgroundColor: Colors.grey.shade300,
value: rest_progress,
strokeWidth: 6,
),
),
AnimatedBuilder(
animation: rest_controller,
builder: (context, child) => Text(
restCountText,
style: TextStyle(
fontSize: 50,
fontWeight: FontWeight.bold,
color: kTextColor,
),
),
),
],
),
),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 20),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
GestureDetector(
onTap: () {
if (rest_controller.isAnimating) {
rest_controller.stop();
setState(() {
rest_isPlaying = false;
});
} else {
rest_controller.reverse(from: rest_controller.value == 0 ? 1.0 : rest_controller.value);
setState(() {
rest_isPlaying = true;
});
}
},
child: RoundButton(
icon: rest_isPlaying == true ? Icons.pause : Icons.play_arrow,
),
),
GestureDetector(
onTap: () {
rest_controller.reset();
setState(() {
rest_isPlaying = false;
});
},
child: RoundButton(
icon: Icons.stop,
),
),
],
),
)
],
),
),
);
}
);
});
}
Basically, setstate from the initstate is not changing the state. I have tried to change the state from showDataAlert function also, but no luck. Only the state changes if I click the button inside the showdialog.