No Animation with AnimatedSwitcher or AnimatedOpacity - flutter

Question

I'm learning flutter and I'm having behavior with the animation system.
I created a Radio Button which is a circle that should get filled when it gets clicked.
I created a stateful widget class and a state class.
In the state class, I build a :
GestureDetector -> Container -> AnimatedSwitcher -> _animatedWidget
_animatedWidget is a Widget that changes when I click (in the GestureDetector onTap I do _changeSelect)
void _changeSelect(){
_isSelected = !_isSelected;
if(_isSelected){
setState(() {
_animatedWidget = Container(width: double.infinity,height: double.infinity,decoration: BoxDecoration(shape: BoxShape.circle, color: Colors.black));
});
}
else{
setState(() {
_animatedWidget = Container();
});
}
}
And this code is not working properly, it should fade in the full container and fade out the empty container but instead, it just pops in and pops out (like a classic change would do)
Here is the full code of my state class :
class _RadioButtonState extends State<RadioButton> {
Widget _animatedWidget = Container();
bool _isSelected = false;
bool isSelected(){
return _isSelected;
}
void _changeSelect(){
_isSelected = !_isSelected;
if(_isSelected){
setState(() {
_animatedWidget = Container(width: double.infinity,height: double.infinity,decoration: BoxDecoration(shape: BoxShape.circle, color: Colors.black));
});
}
else{
setState(() {
_animatedWidget = Container();
});
}
}
#override
Widget build(BuildContext context){
return GestureDetector(
onTap: _changeSelect,
child:
Container(
width: 16.0,
height: 16.0,
padding: EdgeInsets.all(2.0),
decoration: BoxDecoration(
shape: BoxShape.circle,
border: Border.all(width: 2.0, color: Colors.black)
),
child: AnimatedSwitcher(
duration: Duration(seconds: 1),
child: _animatedWidget,
)
),
);
}
}
Note: I also tried with AnimatedOpacity instead of AnimatedSwitcher (with the full Container with a starting opacity of 0 increased to 1 when clicked) but it doesn't even change the view, however, the javascript looks to be working during the duration time

Answer 1

Is this what you're looking for?
Widget _animatedWidget = Container();
bool _isSelected = false;
bool isSelected() {
return _isSelected;
}
void _changeSelect() {
_isSelected = !_isSelected;
if (_isSelected) {
setState(() {
_animatedWidget = Container(
key: ValueKey(1),
width: double.infinity,
height: double.infinity,
decoration: BoxDecoration(shape: BoxShape.circle, color: Colors.black),
);
});
} else {
setState(() {
_animatedWidget = Container(
key: ValueKey(2),
);
});
}
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: Center(
child: GestureDetector(
onTap: _changeSelect,
child: Container(
width: 66.0,
height: 66.0,
padding: EdgeInsets.all(2.0),
decoration: BoxDecoration(shape: BoxShape.circle, border: Border.all(width: 2.0, color: Colors.black)),
child: AnimatedSwitcher(
duration: Duration(seconds: 1),
child: _animatedWidget,
)),
),
),
);
}