Countdown in a ListView (Flutter)

Question

I would like to find a solution to create countdowns from a date and put them in a ListView. I hope this does not slow down the application too much when using it. I already have a code I want to keep, it's a RecyclerView with images and text.

Here's the code, if you need anything else I'll send it to you.

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(),
    ),
    );
  }
}

Thank you!

Update : to add the countdown look this post :Date Countdown Timer

and for the lazy loading, I have changed my ListView to a ListView.builder

Answer 1

Is is suggested to use Listview.builder and not just put a list into ListView if you need lazy loading.

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

Replace the ListView to ListView.builder.

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

Here is the sample code from yours. index is already exist in itemBuilder function.

...
  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,
                    ),
                  ),
                ],
              ),
            )
          ],
        ),
      );
    },
  ),
...