在Flutter中为窗口小部件定义自定义参数

Question

I'm creating a card widget that will be used to create a list of cards. I want to pass a parameter isLastCard to each card, so that I can increase margin for the last card in the list.

I have the following setup:

class CardsIndex extends StatelessWidget {

  Widget _card(context, label, bool isLastCard) {
    const double bottomMargin = isLastCard ? 40.0 : 8.0;

    return new Container(
      margin: const EdgeInsets.fromLTRB(12.0, 8.0, 12.0, bottomMargin),
      child: new Row(
          children: <Widget>[
          new Expanded(
              child: new Text(label),
          ),
          ],
      ),
    );
  }

  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
            title: new Text("Cards"),
        ),
        body: new Container(
          child: new Stack(
            children: [
              new Container(
                child: new ListView(
                  children: <Widget>[
                      _card(context, 'Card 1', false),
                      _card(context, 'Card 2', false),
                      _card(context, 'Card 3', true),
                  ],
                )
              )
            ],
          ),
        ),
    );
  }
}

This gives me this error in the output, for isLastCard inside the turnary: Const variables must be initialized with a constant value.

How do I correctly define isLastCard and bottomMargin in the _card widget?

Thanks!

Answer 1

Figured it out.

I had to define bottomMargin as so: double bottomMargin = isLastCard ? 40.0 : 8.0; double bottomMargin = isLastCard ? 40.0 : 8.0;

And because I was using this to set margin on the container, I had to not define margin as a const , like so: margin: EdgeInsets.fromLTRB(12.0, 8.0, 12.0, bottomMargin)