The parameter cant have a null value about xylophone-flutter-completed

[RileyManda]

I am experiencing an issue with null values on color and soundNumber:The parameter color and soundNumber cant have a null value

Expanded buildKey({Color color,int soundNumber}) {
    return Expanded(
      child: TextButton(
        child: color,
        onPressed: () {
          playSound(soundNumber);
        },
      ),
    );
  }

I ended up resolving this by setting Color as required and soundNumber as nullable:
FlatButton is also deprecated in the latest flutter SDK:
So i have to replace that with TextButton instead.But doing so produces an error on the 'color' widget variable (color: color).

buildKey({required Color color, int? soundNumber}) {
   return Expanded(
     child: FlatButton(
       color: color,
       onPressed: () {
         playSound(soundNumber!);
       }, child: const Text(''),
     ),
   );
 }