Refresh a image and a text flutter

Im using statefull to refresh but i don't know what i have to write in setstate to refresh the slidedialog.

i need to refresh an image that i choose the image in a dialog and it saves in a variable named ex3. this variable is a class with name, image etc etc... so i should refresh that ex3.image and ex3.name

 StatefulBuilder(builder: (context, _setState) {
                    return Container(
                      height: 120.0,
                      width: 120.0,
                      decoration: BoxDecoration(
                        image: DecorationImage(
                          image:
                              ex3?.image ?? AssetImage("assets/images/2.png"),
                          fit: BoxFit.fill,
                        ),
                        shape: BoxShape.circle,
                      ),
                      child: Text(ex3?.nom ?? "ex: Feliz"),
                    );

                    _setState({});
                  }),

I have a class named usermodel and this code is to add the new image and new name so this value ex3.nom (name) and ex3.image update

   ElevatedButton(
                  child: Text(ex3?.nom ?? "Elige como te sientes"),
                  onPressed: () {
                    SelectDialog.showModal<UserModel>(
                      context,
                      label: "¿Como te sientes hoy?",
                      items: modelItems,
                      selectedValue: ex3,
                      itemBuilder: (BuildContext context, UserModel item,
                          bool isSelected) {
                        return Container(
                          decoration: !isSelected
                              ? null
                              : BoxDecoration(
                                  borderRadius: BorderRadius.circular(5),
                                  color: Colors.white,
                                  border: Border.all(
                                      color: Theme.of(context).primaryColor),
                                ),
                          child: ListTile(
                            leading: CircleAvatar(
                                backgroundImage: AssetImage(item.rutaimage!)),
                            selected: isSelected,
                            title: Text(item.nom),
                            subtitle: Text(item.color),
                          ),
                        );
                      },
                      onChange: (selected) {
                        setState(() {
                          ex3 = selected;
                        });
                      },
                    );
                  },
                ),

Use a bool to check if something is true or not you have to use setState in onTap functions or clickable widgets not in container, read this article

class MyWidget extends StatefulWidget {
  const MyWidget({Key key}) : super(key: key);

  @override
  State<MyWidget> createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  bool _flag = false;
  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: () {
        setState(() {
          _flag != _flag;
        });
      },
      child: Container(
        height: 120.0,
        width: 120.0,
        decoration: BoxDecoration(
          image: DecorationImage(
            image: _flag
                ? AssetImage("assets/images/2.png")
                : AssetImage("assets/images/3.png"),
            fit: BoxFit.fill,
          ),
          shape: BoxShape.circle,
        ),
        child: Text(_flag ? "ex: Feliz" : "here is when false"),
      ),
    );
  }
}