Shorts Squadra Squadra 17 Shorts 17 17 Shorts Squadra Squadra vEwqUSE8O

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 {}

Shorts Shorts Squadra 17 17 Squadra Squadra 17 Squadra Shorts // A ListItem that contains data to display a heading
class HeadingItem implements Squadra Shorts Squadra 17 Shorts 17 Squadra 17 Shorts Squadra ListItem {
  final String heading;

  HeadingItem(this.Shorts Squadra 17 17 Squadra Squadra Shorts Shorts Squadra 17 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"),
17 Squadra Shorts 17 Squadra Shorts Squadra Squadra 17 Shorts );

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: Shorts Squadra 17 17 Shorts Squadra 17 Squadra Shorts Squadra (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),
      );
    }
  },Squadra Squadra 17 17 17 Squadra Shorts Squadra Shorts Shorts 
);

Complete example

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

void main() {
  runApp(MyApp(
    items: List<ListItem>.generate(
      1000,
      (i) Squadra Squadra Squadra Shorts Squadra 17 17 17 Shorts Shorts =Squadra Shorts Squadra Squadra Shorts Squadra 17 17 17 Shorts > i % 6 == 0
          ? HeadingItem("Heading $i")
          : MessageItem("Sender $i", "Message body $i"),
    ),
  ));
}

class MyApp extends StatelessWidget {
  final 17 Squadra Shorts Squadra Squadra Shorts 17 17 Squadra Shorts ListSquadra Shorts 17 17 Squadra Squadra Squadra 17 Shorts Shorts <ListItem> items;

  MyApp({Key key17 Squadra 17 Squadra Squadra 17 Shorts Shorts Squadra Shorts ,  this.items}) : super(key: key);

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

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(
          title: Text(titleSquadra Shorts 17 Shorts Squadra Squadra Squadra 17 17 Shorts ),
        ),
        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 = Shorts Shorts Squadra Squadra 17 17 Squadra Squadra 17 Shorts items[index];

            if (item is HeadingItem) {
              return ListTile(
                title:Boutique winter Denim Boutique Gap Gap Denim winter Jacket Jacket Boutique winter RwYdq4U Text(
                  item.heading,
                  style17 Squadra 17 Shorts 17 Squadra Shorts Squadra Squadra Shorts : 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;
  finalwinter Boutique Old Casual Dress Navy ZZdq7 String body;

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