screenSize function
Gets the screen size category of the screen.
Implementation
ScreenSizes screenSize(BuildContext context){
final double width = MediaQuery.of(context).size.width;
if(width < 400){
return ScreenSizes.small;
}else if(width > 401 && width < 800){
return ScreenSizes.medium;
}else{
return ScreenSizes.large;
}
}