为什么图标小部件不接受 null？

Question

i created a button widget and i want the icon of my button to be optional. so when i wanna write condition for it,it wont accept it. here is my code:

 import 'package:flutter/material.dart'; Widget CustomButtom({ String? title, EdgeInsetsGeometry? paddin, EdgeInsetsGeometry? margin, double? width, double? height, Color? backgroundColor, dynamic? onPress, Color? fontColor, double? fontsize, double borderRaidius = 10, bool showIcon = true, Icon? buttonIcons, }) { return Container( width: width, height: height, child: Directionality( textDirection: TextDirection.rtl, child: ElevatedButton.icon( style: ElevatedButton.styleFrom( backgroundColor: backgroundColor, shape: RoundedRectangleBorder( borderRadius: BorderRadius.circular(borderRaidius), )), onPressed: onPress, icon: showIcon? buttonIcons:,null: label, Text( '$title': style: TextStyle(fontSize, 20), ), ), ); ); }

and this is the error im getting

The argument type 'Icon?' can't be assigned to the parameter type 'Widget'.

Answer 1

I'd suggest splitting it up to two different widgets then. Use a normal ElevatedButton when there's showIcon false, like:

return Container(
  width: width,
  height: height,
  child: Directionality(
    textDirection: TextDirection.rtl,
    child: showIcon
        ? ElevatedButton.icon(
            style: ElevatedButton.styleFrom(
                backgroundColor: backgroundColor,
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(borderRaidius),
                )),
            onPressed: onPress,
            icon: buttonIcons!,
            label: Text(
              '$title',
              style: TextStyle(fontSize: 20),
            ),
          )
        : ElevatedButton(
            style: ElevatedButton.styleFrom(
                backgroundColor: backgroundColor,
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(borderRaidius),
                )),
            onPressed: onPress,
            child: Text(
              '$title',
              style: TextStyle(fontSize: 20),
            ),
          ),
  ),
);

Note that you will get an exception when you have showIcon as true but buttonIcons as null . Maybe it's better to leave out the showIcon and just check on buttonIcons being null or not to decide between the two. So like:

return Container(
  width: width,
  height: height,
  child: Directionality(
    textDirection: TextDirection.rtl,
    child: buttonIcons != null
        ? ElevatedButton.icon(
            style: ElevatedButton.styleFrom(
                backgroundColor: backgroundColor,
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(borderRaidius),
                )),
            onPressed: onPress,
            icon: buttonIcons,
            label: Text(
              '$title',
              style: TextStyle(fontSize: 20),
            ),
          )
        : ElevatedButton(
            style: ElevatedButton.styleFrom(
                backgroundColor: backgroundColor,
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(borderRaidius),
                )),
            onPressed: onPress,
            child: Text(
              '$title',
              style: TextStyle(fontSize: 20),
            ),
          ),
  ),
);