ListView 中的倒计时 (Flutter)

Question

我想找到一种解决方案来从日期创建倒计时并将它们放在 ListView 中。我希望这不会在使用它时过多地减慢应用程序的速度。 我已经有一个想要保留的代码，它是一个带有图像和文本的 RecyclerView。

这是代码，如果你需要什么我会发给你。

import 'package:flutter/material.dart';
import 'package:cached_network_image/cached_network_image.dart';
import '../recyclerview/data.dart';
import 'package:watch/constants.dart';


class ListViewExample extends StatefulWidget {
  @override 
  State<StatefulWidget> createState() {
    return new ListViewExampleState(
    );
  }
}

class ListViewExampleState extends State<ListViewExample>{
  List<Container> _buildListItemsFromItems(){
    int index = 0;
    return item.map((item){

      var container = Container(
        decoration: index % 2 == 0?
        new BoxDecoration(color: const Color(0xFFFFFFFF)):
          new BoxDecoration(
            color: const Color(0xFFFAFAF5)
          ),
        child: new Row(
          children: <Widget>[
            new Container(
              margin: new EdgeInsets.all(5.0),
              child: new CachedNetworkImage(
                imageUrl: item.imageURL,
                width: 200.0,
                height: 100.0,
                fit: BoxFit.cover,
              ),
            ),
            Expanded(
              child: Row(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                Container(
                  padding: const EdgeInsets.only(bottom: 75.0 ),
                  child: Text(
                    item.title,
                    style: kItemTitle,
                  ),
                ),
                Container(
                  padding: const EdgeInsets.only(left: 15.0),
                  child:Text(
                    item.description,
                    style: kItemDescription,
                  ),
                ),
                ]),
            )
          ],
        )
      );
      index = index + 1;
      return container;
    }).toList();
  }
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
       appBar: AppBar(
         title: Text('Accueil', style: kAppBarStyle,),
          backgroundColor: Colors.white,  
          elevation: 0,
       ),
       body: ListView(
      children: _buildListItemsFromItems(),
    ),
    );
  }
}

谢谢！

更新：添加倒计时看这个帖子：Date Countdown Timer

对于延迟加载，我已将 ListView 更改为 ListView.builder

Answer 1

如果需要延迟加载，建议使用Listview.builder，而不是只将列表放入ListView。

https://flutter.dev/docs/cookbook/lists/long-lists

将ListView 替换为ListView.builder。

ListView.builder(
    itemCount: // items.length
    itemBuilder: (buildContext, index) {}, // define what Widget for each index
)

这是您的示例代码。 itemBuilder 函数中已经存在索引。

...
  body: ListView.builder(
    itemCount: items.length,
    itemBuilder: (buildContext, index) {
      return Container(
        decoration: index % 2 == 0
            ? new BoxDecoration(color: const Color(0xFFFFFFFF))
            : new BoxDecoration(color: const Color(0xFFFAFAF5)),
        child: new Row(
          children: <Widget>[
            new Container(
              margin: new EdgeInsets.all(5.0),
              child: new CachedNetworkImage(
                imageUrl: item.imageURL,
                width: 200.0,
                height: 100.0,
                fit: BoxFit.cover,
              ),
            ),
            Expanded(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  Container(
                    padding: const EdgeInsets.only(bottom: 75.0),
                    child: Text(
                      items[index].title,
                    ),
                  ),
                  Container(
                    padding: const EdgeInsets.only(left: 15.0),
                    child: Text(
                      items[index].description,
                    ),
                  ),
                ],
              ),
            )
          ],
        ),
      );
    },
  ),
...