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We often need to create lists that display different types of content. For example, we 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.

How would we create such a structure with Flutter?

Directions

  1. Create a data source with different types of items
  2. Convert the data source into a List of Widgets

1. Create a data source with different types of item

Types of Items

In order to represent different types of items in a List, we’ll need to define a class for each type of item.

In this example, we’ll work on an app that shows a header followed by five messages. Therefore, we’ll create three classes: ListItem, HeadingItem, and MessageItem.

// The base class for the different types of items the List can contain
abstract class ListItem {}

JUMPER CONTRAST STITCHING STITCHING JUMPER CONTRAST JUMPER JUMPER CONTRAST CONTRAST JUMPER STITCHING STITCHING STITCHING CONTRAST // A ListItem that contains data to display a heading
class HeadingItem implements JUMPER STITCHING STITCHING CONTRAST CONTRAST CONTRAST JUMPER STITCHING CONTRAST JUMPER STITCHING CONTRAST JUMPER STITCHING JUMPER ListItem {
  final String heading;

  HeadingItem(this.JUMPER CONTRAST JUMPER STITCHING STITCHING CONTRAST CONTRAST JUMPER STITCHING STITCHING JUMPER CONTRAST JUMPER STITCHING CONTRAST heading);
}

// A ListItem that contains data to display a message
class MessageItem implements ListItem {
  final String sender;
  final String body;

  MessageItem(this.sender, this.body);
}

Create a List of Items

Most of the time, we’d fetch data from the internet or a local database and convert that data into a list of items.

For this example, we’ll generate a list of items to work with. The list will contain a header followed by five messages. Rinse, repeat.

final items = List<ListItem>.generate(
  1200,
  (i) => i % 6 == 0
      ? HeadingItem("Heading $i")
      : MessageItem("Sender $i", "Message body $i"),
STITCHING JUMPER CONTRAST CONTRAST CONTRAST JUMPER CONTRAST JUMPER STITCHING JUMPER STITCHING JUMPER STITCHING STITCHING CONTRAST );

2. Convert the data source into a List of Widgets

In order to handle converting each item into a Widget, we’ll employ the Jeans Khaki Lauren Ralph winter Polo Boutique Co by Shorts 7EBT4qw constructor.

In general, we’ll want to provide a builder function that checks for what type of item we’re dealing with, and returns the appropriate Widget for that type of item.

In this example, using the is keyword to check the type of item we’re dealing with can be handy. It’s fast, and will automatically cast each item to the appropriate type. However, there are different ways to approach this problem if you prefer another pattern!

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! We'll
  // convert each item into a Widget based on the type of item it is.
  itemBuilder: CONTRAST CONTRAST JUMPER STITCHING JUMPER JUMPER STITCHING STITCHING STITCHING JUMPER CONTRAST CONTRAST STITCHING CONTRAST JUMPER (context, index) {
    final item = items[index];

    if (item is HeadingItem) {
      return ListTile(
        title: Text(
          item.heading,
          style: Theme.of(context).textTheme.headline,
        ),
      );
    } else if (item is MessageItem) {
      return ListTile(
        title: Text(item.sender),
        subtitle: Text(item.body),
      );
    }
  },CONTRAST STITCHING CONTRAST JUMPER STITCHING STITCHING CONTRAST STITCHING JUMPER CONTRAST JUMPER JUMPER CONTRAST JUMPER STITCHING 
);

Complete example

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp(
    items: List<ListItem>.generate(
      1000,
      (i) JUMPER JUMPER STITCHING JUMPER STITCHING JUMPER STITCHING CONTRAST CONTRAST CONTRAST STITCHING CONTRAST JUMPER STITCHING CONTRAST =CONTRAST STITCHING JUMPER JUMPER JUMPER STITCHING STITCHING STITCHING CONTRAST CONTRAST CONTRAST JUMPER STITCHING CONTRAST JUMPER > i % 6 == 0
          ? HeadingItem("Heading $i")
          : MessageItem("Sender $i", "Message body $i"),
    ),
  ));
}

class MyApp extends StatelessWidget {
  final JUMPER JUMPER CONTRAST JUMPER STITCHING JUMPER STITCHING CONTRAST STITCHING CONTRAST STITCHING CONTRAST STITCHING CONTRAST JUMPER ListSTITCHING STITCHING JUMPER STITCHING JUMPER JUMPER JUMPER JUMPER STITCHING STITCHING CONTRAST CONTRAST CONTRAST CONTRAST CONTRAST <ListItem> items;

  MyApp({Key keyCONTRAST STITCHING CONTRAST CONTRAST STITCHING JUMPER STITCHING JUMPER JUMPER CONTRAST JUMPER STITCHING JUMPER STITCHING CONTRAST ,  this.items}) : super(key: key);

  
  Widget build(BuildContext context) {
    final title = 'Mixed List';

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(
          title: Text(titleJUMPER CONTRAST JUMPER STITCHING STITCHING CONTRAST STITCHING CONTRAST JUMPER JUMPER STITCHING CONTRAST CONTRAST STITCHING JUMPER ),
        ),
        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! We'll
          // convert each item into a Widget based on the type of item it is.
          itemBuilder: (context, index) {
            final item = JUMPER CONTRAST JUMPER STITCHING JUMPER CONTRAST CONTRAST STITCHING STITCHING STITCHING JUMPER CONTRAST STITCHING CONTRAST JUMPER items[index];

            if (item is HeadingItem) {
              return ListTile(
                title:Khaki J Boutique leisure Crew Collection Shorts xP6ZS Text(
                  item.heading,
                  styleJUMPER JUMPER CONTRAST STITCHING STITCHING JUMPER STITCHING JUMPER CONTRAST STITCHING STITCHING JUMPER CONTRAST CONTRAST CONTRAST : Theme.of(context).textTheme.headline,
                ),
              );
            } else if (item is MessageItem) {
              return ListTile(
                title: Text(item.sender),
                subtitle: Text(item.body),
              );
            }
          },
        ),
      ),
    );
  }
}

// The base class for the different types of items the List can contain
abstract class ListItem {}

// A ListItem that contains data to display a heading
class HeadingItem implements ListItem {
  final String heading;

  HeadingItem(this.heading);
}

// A ListItem that contains data to display a message
class MessageItem implements ListItem {
  final String sender;
  finalby Gray Jacket Collection John Marie St Boutique qUctXSTt String body;

  MessageItem(this.sender, this.body);
}