Another exception was thrown: Null check operator used on a null value

Question

i need to use a future builder to get the value of a radio button form shared preferences. but the error occurs when i open the page of the radio button is:

Another exception was thrown: Null check operator used on a null value 

the radio button widget is:

FutureBuilder<bool>(
                          future: getDayNotificationIsOn(),
                          builder: (context, snapshot) {
                            return NeumorphicSwitch(
                              value: snapshot.data!,
                              style: NeumorphicSwitchStyle(
                                thumbShape: NeumorphicShape.flat,
                                activeTrackColor: const Color(0xff257864),
                              ),
                              onChanged: (value) async {
                                setState(() {});
                                //sharedPreferences
                                await setDayNotificationIsOn(value);
                              },
                            );
                          }),

the function used in future builder to get the value of the radio button:

  Future<bool> getDayNotificationIsOn() async {
    SharedPreferences _pref = await SharedPreferences.getInstance();
    return  _pref.getBool('dayNotificationIsOn') ?? false;
  }

Answer 1

You should add a check before NeumorphicSwitch to make sure the snapshot has data by adding if (snapshot.hasData).