Question

我遇到错误错误使用ParentDataWidget。

Mobile App

错误代码是

import 'package:flutter/material.dart';
import 'package:font_awesome_flutter/font_awesome_flutter.dart';
import 'package:testapp/constants.dart';
import 'package:testapp/request/quotation_resources.dart';
import 'dart:math';

class AuctionDetails extends StatelessWidget {
  final QuotationResources quotationResources;

  const AuctionDetails({Key key, this.quotationResources}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: kPrimaryColor,
      appBar: buildAppBar,
      body: BodyAuction(),
    );
  }

  AppBar get buildAppBar {
    return AppBar(
      backgroundColor: kBackgroundColor,
      elevation: 0,
      leading: Padding(
        padding: EdgeInsets.only(left: kDefaultPadding),
        child:
            IconButton(icon: Icon(FontAwesomeIcons.backward), onPressed: () {}),
      ),
    );
  }
}

class BodyAuction extends StatelessWidget {
  final QuotationResources quotationResources;

  const BodyAuction({Key key, this.quotationResources}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    Size size = MediaQuery.of(context).size;
    var cardAspectRatio = 10.0 / 14.0;
    var widgetAspectRatio = cardAspectRatio * 1.2;
    return Column(
      children: <Widget>[
        Container(
          padding: EdgeInsets.symmetric(horizontal: kDefaultPadding),
          decoration: BoxDecoration(
            color: kBackgroundColor,
            borderRadius: BorderRadius.only(
              bottomLeft: Radius.circular(50),
              bottomRight: Radius.circular(50),
            ),
          ),
          child: Column(
            children: <Widget>[
              Container(
                margin: EdgeInsets.symmetric(vertical: kDefaultPadding),
                height: size.width * 0.8,
                child: CardSlider(),
              ),
            ],
          ),
        ),
      ],
    );
  }
}

class CardSlider extends StatefulWidget {
  @override
  _CardSliderState createState() => _CardSliderState();
}

var cardAspectRatio = 10.0 / 14.0;
var widgetAspectRatio = cardAspectRatio * 1.2;

class _CardSliderState extends State<CardSlider> {
  var currentPage = images.length - 1.0;
  @override
  Widget build(BuildContext context) {
    PageController controller = PageController(initialPage: images.length - 1);
    controller.addListener(() {
      setState(() {
        currentPage = controller.page;
      });
    });
    return Column(
      children: <Widget>[
        CardScrollWidget(currentPage),
        Positioned.fill(
          child: PageView.builder(
            itemCount: images.length,
            controller: controller,
            reverse: true,
            itemBuilder: (context, index) {
              return Container();
            },
          ),
        )
      ],
    );
  }
}

class CardScrollWidget extends StatelessWidget {
  var currentPage;
  var padding = 20.0;
  var verticalInset = 20.0;

  CardScrollWidget(this.currentPage);

  @override
  Widget build(BuildContext context) {
    return new AspectRatio(
      aspectRatio: widgetAspectRatio,
      child: LayoutBuilder(builder: (context, contraints) {
        var width = contraints.maxWidth;
        var height = contraints.maxHeight;

        var safeWidth = width - 2 * padding;
        var safeHeight = height - 2 * padding;

        var heightOfPrimaryCard = safeHeight;
        var widthOfPrimaryCard = heightOfPrimaryCard * cardAspectRatio;

        var primaryCardLeft = safeWidth - widthOfPrimaryCard;
        var horizontalInset = primaryCardLeft / 2;

        List<Widget> cardList = new List();

        for (var i = 0; i < images.length; i++) {
          var delta = i - currentPage;
          bool isOnRight = delta > 0;

          var start = padding +
              max(
                  primaryCardLeft -
                      horizontalInset * -delta * (isOnRight ? 15 : 1),
                  0.0);

          var cardItem = Positioned.directional(
            top: padding + verticalInset * max(-delta, 0.0),
            bottom: padding + verticalInset * max(-delta, 0.0),
            start: start,
            textDirection: TextDirection.rtl,
            child: ClipRRect(
              borderRadius: BorderRadius.circular(16.0),
              child: Container(
                decoration: BoxDecoration(color: Colors.white, boxShadow: [
                  BoxShadow(
                      color: Colors.black12,
                      offset: Offset(3.0, 6.0),
                      blurRadius: 10.0)
                ]),
                child: AspectRatio(
                  aspectRatio: cardAspectRatio,
                  child: Stack(
                    fit: StackFit.expand,
                    children: <Widget>[
                      Image.asset(images[i], fit: BoxFit.cover),
                      Align(
                        alignment: Alignment.bottomLeft,
                      )
                    ],
                  ),
                ),
              ),
            ),
          );
          cardList.add(cardItem);
        }
        return Stack(
          children: cardList,
        );
      }),
    );
  }
}

Answer 1

错误代码已经显示出什么地方不对。 “定位的窗口小部件直接放置在堆栈窗口小部件中。有问题的“位置”当前放置在“列”窗口小部件中。”您必须将Positioned Widget放置在Stacks中。您不能将它们放在“列”中。

Column(
      children: <Widget>[
        CardScrollWidget(currentPage),
        Positioned.fill(
          child: PageView.builder(
            itemCount: images.length,
            controller: controller,
            reverse: true,
            itemBuilder: (context, index) {
              return Container();
            },
          ),
        )
      ],
    );

只需将Stack替换为Stack或不使用Positioned.fill。

不正确使用ParentDataWidget。 -如何解决？

1 个答案: