Flutter

class MyCard extends StatelessWidget {
    Widget ?title;
    Widget ?icon;
    MyCard({Key? key, this.title, this.icon});

    @ override
      Widget build(BuildContext context) {
        return Container(
          child: Card(
            child: Column(
              children: <Widget>[
                title,
                icon
              ],
            ),
          ),
        );
      }
}

I get the following error: A value of type 'Widget?' can't be assigned to a variable of type 'Widget' because 'Widget?' is nullable and 'Widget' isn't.

How can I resolve this issue?

CodePudding user response：

Because your title and icon can be null at runtime but Column() does not allow you to add Widgets in children that are going to be null.

You can add a null check on your title like this title! and the same for icon to icon! or you can give a constant Widget to your title and icon when they comes as null at runtime. Something like this

Column(
  children: <Widget>[
    title ?? const Offstage(),
    icon ?? const Offstage(),
  ],
),