showCountryPickerSheet function Null safety

Future<Country?> showCountryPickerSheet(
  1. BuildContext context,
  2. {Widget? title,
  3. Widget? cancelWidget,
  4. double cornerRadius = 35,
  5. bool focusSearchBox = false,
  6. double heightFactor = 0.9}
)

Implementation

Future<Country?> showCountryPickerSheet(BuildContext context,
    {Widget? title,
    Widget? cancelWidget,
    double cornerRadius: 35,
    bool focusSearchBox: false,
    double heightFactor: 0.9}) {
  assert(heightFactor <= 0.9 && heightFactor >= 0.4,
      'heightFactor must be between 0.4 and 0.9');
  return showModalBottomSheet<Country?>(
      context: context,
      isScrollControlled: true,
      shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.only(
              topLeft: Radius.circular(cornerRadius),
              topRight: Radius.circular(cornerRadius))),
      builder: (_) {
        return Container(
          height: MediaQuery.of(context).size.height * heightFactor,
          child: Column(
            children: <Widget>[
              SizedBox(height: 16),
              Stack(
                children: <Widget>[
                  cancelWidget ??
                      Positioned(
                        right: 8,
                        top: 4,
                        bottom: 0,
                        child: TextButton(
                            child: Text('Cancel'),
                            onPressed: () => Navigator.pop(context)),
                      ),
                  Center(
                    child: title ??
                        Text(
                          'Choose region',
                          textAlign: TextAlign.center,
                          style: TextStyle(
                            fontSize: 25,
                            fontWeight: FontWeight.w500,
                          ),
                        ),
                  ),
                ],
              ),
              SizedBox(height: 16),
              Expanded(
                child: CountryPickerWidget(
                  onSelected: (country) => Navigator.of(context).pop(country),
                ),
              ),
            ],
          ),
        );
      });
}