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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 {}

DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck DSQUARED2 Turtleneck Turtleneck DSQUARED2 Turtleneck Turtleneck DSQUARED2 // A ListItem that contains data to display a heading
class HeadingItem implements DSQUARED2 Turtleneck DSQUARED2 DSQUARED2 Turtleneck Turtleneck Turtleneck DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck ListItem {
  final String heading;

  HeadingItem(this.Turtleneck DSQUARED2 Turtleneck DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck Turtleneck DSQUARED2 DSQUARED2 Turtleneck 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"),
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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: Turtleneck Turtleneck DSQUARED2 DSQUARED2 Turtleneck DSQUARED2 Turtleneck DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck (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),
      );
    }
  },DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck Turtleneck Turtleneck DSQUARED2 Turtleneck DSQUARED2 Turtleneck DSQUARED2 
);

Complete example

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

void main() {
  runApp(MyApp(
    items: List<ListItem>.generate(
      1000,
      (i) DSQUARED2 Turtleneck Turtleneck DSQUARED2 Turtleneck Turtleneck Turtleneck DSQUARED2 DSQUARED2 DSQUARED2 DSQUARED2 =Turtleneck DSQUARED2 Turtleneck Turtleneck Turtleneck DSQUARED2 Turtleneck DSQUARED2 DSQUARED2 DSQUARED2 DSQUARED2 > i % 6 == 0
          ? HeadingItem("Heading $i")
          : MessageItem("Sender $i", "Message body $i"),
    ),
  ));
}

class MyApp extends StatelessWidget {
  final DSQUARED2 DSQUARED2 DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck Turtleneck Turtleneck Turtleneck Turtleneck DSQUARED2 ListDSQUARED2 Turtleneck Turtleneck DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck DSQUARED2 Turtleneck DSQUARED2 Turtleneck <ListItem> items;

  MyApp({Key keyDSQUARED2 DSQUARED2 DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck Turtleneck Turtleneck Turtleneck DSQUARED2 Turtleneck ,  this.items}) : super(key: key);

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

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(
          title: Text(titleTurtleneck DSQUARED2 DSQUARED2 DSQUARED2 Turtleneck Turtleneck DSQUARED2 DSQUARED2 Turtleneck DSQUARED2 Turtleneck ),
        ),
        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 = Turtleneck Turtleneck DSQUARED2 Turtleneck DSQUARED2 DSQUARED2 Turtleneck Turtleneck DSQUARED2 DSQUARED2 DSQUARED2 items[index];

            if (item is HeadingItem) {
              return ListTile(
                title:Short Short Sleeve Olive Tee Tee Sleeve Short Olive Sleeve Tee Short Olive Sleeve 6a6wZq Text(
                  item.heading,
                  styleDSQUARED2 DSQUARED2 Turtleneck DSQUARED2 DSQUARED2 Turtleneck DSQUARED2 DSQUARED2 Turtleneck Turtleneck Turtleneck : 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;
  finalShorts leisure Boutique Boutique Boutique Boutique Shorts leisure Shorts Express Express leisure Express adqawf String body;

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