flutter: dropdown item programmatically unselect problem - flutter

Question

I use two dropdown menu here.
Both data come from API. And second's one data depends on first dropdown items. Thats mean when I select an item from first menu then data will come on second dropdown's. And It's changing dynamically.
I face a problem here. When I change a items from first dropdown, second dropdown show me a error.
Like this -
Before
After Change City value
Here is my Code for two dropdown
// Choose City
CustomDropDownMenu(
items: allCity.map((list) {
return DropdownMenuItem(
child: Padding(
padding: const EdgeInsets.only(left: 20.0),
child: Text(
"${list["name"]}",
style: TextStyle(),
),
),
onTap: () {
setState(() {
isVisible = false;
});
getWeight(list["id"]).then((value) => {
setState(() {}),
});
print(list["id"]);
FocusScope.of(context).unfocus();
print(weightList.length);
},
value: list["id"].toString(),
);
}).toList(),
value: _city,
hint: "Choose City",
onChanged: (value) {
setState(() {
this._city = value;
});
},
),
// Weight
CustomDropDownMenu(
hint: "Select Weight",
value: _weight,
items: [
DropdownMenuItem(child: Text("Select Weight")),
...weightList.map((list) {
return DropdownMenuItem(
child: Padding(
padding: const EdgeInsets.only(left: 20.0),
child: Text(
"${list["weight"]}",
style: TextStyle(),
),
),
onTap: () {
FocusScope.of(context).unfocus();
},
value: list["id"].toString(),
);
}).toList()
],
onChanged: (value) {
setState(() {
_weight = value;
});
},
),
Here is CustomDropDown() class
.. class CustomDropDownMenu extends StatelessWidget { final String hint; final dynamic value;
final Function onChanged; final Function onSaved; final List<DropdownMenuItem<dynamic>> items;
const CustomDropDownMenu({
Key key,
this.hint,
this.onChanged,
this.onSaved,
this.items,
this.value, }) : super(key: key); #override Widget build(BuildContext context) {
double _width = MediaQuery.of(context).size.width;
return Container(
decoration: BoxDecoration(
shape: BoxShape.rectangle,
borderRadius: BorderRadius.all(
Radius.circular(60),
),
),
child: Card(
shape: StadiumBorder(),
elevation: 5,
child: DropdownButtonFormField(
style: TextStyle(
fontWeight: FontWeight.bold,
fontSize: 18.0,
color: Colors.black),
hint: Padding(
padding: const EdgeInsets.only(left: 20.0),
child: Text(
hint,
textAlign: TextAlign.end,
),
),
decoration: InputDecoration(
enabledBorder: UnderlineInputBorder(
borderSide: BorderSide(color: Colors.transparent),
),
),
value: value,
onChanged: onChanged,
onSaved: onSaved,
items: items,
),
)); } }
That's why I want to unselect second's on dropdown menu items programmatically, but not find a solution. Please some one help me.

Answer 1

set _weight value null on city change

Answer 2

Convert your CustomDropDownMenu into StatefulWidget and implement below code:
#override
void didUpdateWidget(covariant AppDropDown oldWidget) {
super.didUpdateWidget(oldWidget);
if (!listEquals(oldWidget.items, widget.items)) {
value = null;
}}