okButton method Null safety

Widget okButton(
  1. Future<void> okPressed(
      )?
    )

    A dialogue 'OK' button which executes okPressed when pressed.

    Implementation

    static Widget okButton(Future<void> Function()? okPressed) {
  return TextButton(
    onPressed: okPressed == null
        ? null
        : () async {
            await okPressed();
          },
    child: const Text('OK'),
    style: ButtonStyle(
      foregroundColor: MaterialStateProperty.all(Colors.black),
    ),
  );
}