Add item to ListView android
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You might need to create lists that display different types of content. For example, you might be working on a list that shows a heading followed by a few items related to the heading, followed by another heading, and so on. Show Heres how you can create such a structure with Flutter:
1. Create a data source with different types of itemsTypes of itemsTo represent different types of items in a list, define a class for each type of item. In this example, create an app that shows a header followed by five messages. Therefore, create three classes: ListItem, HeadingItem, and MessageItem. /// The base class for the different types of items the list can contain.
abstract class ListItem {
/// The title line to show in a list item.
Widget buildTitle(BuildContext context);
/// The subtitle line, if any, to show in a list item.
Widget buildSubtitle(BuildContext context);
}
/// A ListItem that contains data to display a heading.
class HeadingItem implements ListItem {
final String heading;
HeadingItem(this.heading);
@override
Widget buildTitle(BuildContext context) {
return Text(
heading,
style: Theme.of(context).textTheme.headline5,
);
}
@override
Widget buildSubtitle(BuildContext context) => const SizedBox.shrink();
}
/// A ListItem that contains data to display a message.
class MessageItem implements ListItem {
final String sender;
final String body;
MessageItem(this.sender, this.body);
@override
Widget buildTitle(BuildContext context) => Text(sender);
@override
Widget buildSubtitle(BuildContext context) => Text(body);
} Create a list of itemsMost of the time, you would fetch data from the internet or a local database and convert that data into a list of items. For this example, generate a list of items to work with. The list contains a header followed by five messages. Each message has one of 3 types: ListItem, HeadingItem, or MessageItem. final items = List.generate(
1000,
(i) => i % 6 == 0
? HeadingItem('Heading $i')
: MessageItem('Sender $i', 'Message body $i'),
); To convert each item into a widget, use the ListView.builder() constructor. In general, provide a builder function that checks for what type of item youre dealing with, and returns the appropriate widget for that type of item. ListView.builder(
// Let the ListView know how many items it needs to build.
itemCount: items.length,
// Provide a builder function. This is where the magic happens.
// Convert each item into a widget based on the type of item it is.
itemBuilder: (context, index) {
final item = items[index];
return ListTile(
title: item.buildTitle(context),
subtitle: item.buildSubtitle(context),
);
},
) Interactive exampleimport 'package:flutter/material.dart'; void main() { runApp( MyApp( items: List.generate( 1000, (i) => i % 6 == 0 ? HeadingItem('Heading $i') : MessageItem('Sender $i', 'Message body $i'), ), ), ); } class MyApp extends StatelessWidget { final List items; const MyApp({Key? key, required this.items}) : super(key: key); @override Widget build(BuildContext context) { const title = 'Mixed List'; return MaterialApp( title: title, home: Scaffold( appBar: AppBar( title: const Text(title), ), body: ListView.builder( // Let the ListView know how many items it needs to build. itemCount: items.length, // Provide a builder function. This is where the magic happens. // Convert each item into a widget based on the type of item it is. itemBuilder: (context, index) { final item = items[index]; return ListTile( title: item.buildTitle(context), subtitle: item.buildSubtitle(context), ); }, ), ), ); } } /// The base class for the different types of items the list can contain. abstract class ListItem { /// The title line to show in a list item. Widget buildTitle(BuildContext context); /// The subtitle line, if any, to show in a list item. Widget buildSubtitle(BuildContext context); } /// A ListItem that contains data to display a heading. class HeadingItem implements ListItem { final String heading; HeadingItem(this.heading); @override Widget buildTitle(BuildContext context) { return Text( heading, style: Theme.of(context).textTheme.headline5, ); } @override Widget buildSubtitle(BuildContext context) => const SizedBox.shrink(); } /// A ListItem that contains data to display a message. class MessageItem implements ListItem { final String sender; final String body; MessageItem(this.sender, this.body); @override Widget buildTitle(BuildContext context) => Text(sender); @override Widget buildSubtitle(BuildContext context) => Text(body); } |
