State and cities drop down not working after selecting the country

Describe the bug
I followed your documentation and try to use it but i am unable to click on states and cities after i select on country. I followed the same example shown on pub my code looks like

/// Variables to store country state city data in onChanged method.
String countryValue = "";
String stateValue = "";
String cityValue = "";
String address = "";
@OverRide
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: Center(
child: Container(
padding: EdgeInsets.symmetric(horizontal: 20),
height: 600,
child: Column(
children: [
CSCPicker(
showStates: true,
showCities: false,
flagState: CountryFlag.DISABLE,
dropdownDecoration: BoxDecoration(
borderRadius: const BorderRadius.all(
Radius.circular(20),
),
color: Colors.white,
border: Border.all(color: Colors.grey.shade300, width: 1)),
disabledDropdownDecoration: BoxDecoration(
borderRadius: BorderRadius.all(Radius.circular(10)),
color: Colors.grey.shade300,
border: Border.all(color: Colors.grey.shade300, width: 1)),

            ///placeholders for dropdown search field
            countrySearchPlaceholder: "Country",
            stateSearchPlaceholder: "State",
            citySearchPlaceholder: "City",

            ///labels for dropdown
            countryDropdownLabel: "Country",
            stateDropdownLabel: "State",
            cityDropdownLabel: "City",

            ///Country Filter [OPTIONAL PARAMETER]
            countryFilter: [
              CscCountry.India,
              CscCountry.United_States,
              CscCountry.Canada
            ],

            ///selected item style [OPTIONAL PARAMETER]
            selectedItemStyle: TextStyle(
              color: Colors.black,
              fontSize: 14,
            ),

            ///DropdownDialog Heading style [OPTIONAL PARAMETER]
            dropdownHeadingStyle: TextStyle(
                color: Colors.black, fontSize: 17, fontWeight: FontWeight.bold),

            ///DropdownDialog Item style [OPTIONAL PARAMETER]
            dropdownItemStyle: TextStyle(
              color: Colors.black,
              fontSize: 14,
            ),

            dropdownDialogRadius: 10.0,

            ///Search bar radius [OPTIONAL PARAMETER]
            searchBarRadius: 10.0,

            ///triggers once country selected in dropdown
            onCountryChanged: (value) {
              setState(() {
                ///store value in country variable
                countryValue = value;
              });
            },

            ///triggers once state selected in dropdown
            onStateChanged: (value) {
              setState(() {
                ///store value in state variable
                stateValue = value!;
              });
            },

            ///triggers once city selected in dropdown
            onCityChanged: (value) {
              setState(() {
                ///store value in city variable
                cityValue = value!;
              });
            },
          ),
          TextButton(
              onPressed: () {
                setState(() {
                  address = "$cityValue, $stateValue, $countryValue";
                });
              },
              child: Text("Print Data")),
          Text(address)
        ],
      ),
    ),
  ),
);

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
I must be able to select the cities and states as well after i select on the country

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[http-rixhi]

I'm also facing the same issue... after selecting country there is no dropdown for state and city!!

[atvbasha]

any solution??

[nikhil0304hande]

The value of stateValue and cityValue are nullables and hence we need to use null-aware operator and assign a default value. Replace value with value ?? "".
Example:
onStateChanged: (value) {
setState(() {
stateValue = value ?? "";
});
},