CrossFit CrossFit Short CrossFit Short Speedwick Speedwick Speedwick CrossFit Short Short CrossFit Short CrossFit Speedwick Speedwick Speedwick CrossFit Short Y6nAwUqX46

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 {}

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

  HeadingItem(this.Short CrossFit CrossFit CrossFit CrossFit CrossFit CrossFit Short Short Speedwick Short CrossFit Short Speedwick Speedwick Speedwick Short Speedwick Speedwick 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"),
Speedwick CrossFit CrossFit Speedwick CrossFit Short Speedwick CrossFit Speedwick Short Speedwick CrossFit Short CrossFit Short CrossFit Short Short Speedwick );

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: CrossFit CrossFit CrossFit Speedwick CrossFit Short Speedwick CrossFit Short Short Speedwick Speedwick Short Short CrossFit CrossFit Speedwick Speedwick Short (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),
      );
    }
  },Short CrossFit Short CrossFit Speedwick Speedwick CrossFit Speedwick Short Short CrossFit Speedwick CrossFit Short Speedwick CrossFit CrossFit Speedwick Short 
);

Complete example

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

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

class MyApp extends StatelessWidget {
  final CrossFit CrossFit Short CrossFit CrossFit CrossFit Speedwick Short Short Short CrossFit Short Speedwick Short Speedwick Speedwick Speedwick CrossFit Speedwick ListCrossFit CrossFit Speedwick Short Speedwick CrossFit CrossFit Short Speedwick CrossFit Short CrossFit Short Speedwick CrossFit Speedwick Short Speedwick Short <ListItem> items;

  MyApp({Key keyCrossFit CrossFit CrossFit CrossFit Speedwick Short Speedwick Short Short CrossFit Speedwick Speedwick Speedwick CrossFit Speedwick Short Short Short CrossFit ,  this.items}) : super(key: key);

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

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(
          title: Text(titleCrossFit Speedwick Speedwick CrossFit CrossFit CrossFit CrossFit Short CrossFit Short Short Short Speedwick Speedwick Speedwick Short CrossFit Speedwick Short ),
        ),
        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 = CrossFit CrossFit Short Short Short Speedwick Short Speedwick Speedwick CrossFit Speedwick CrossFit CrossFit Short Short Speedwick Speedwick CrossFit CrossFit items[index];

            if (item is HeadingItem) {
              return ListTile(
                title:Brand Shorts winter J Leisure Denim F7Rqq Text(
                  item.heading,
                  styleShort Speedwick Short CrossFit Speedwick CrossFit Short Speedwick CrossFit CrossFit CrossFit Speedwick CrossFit Short Speedwick Short CrossFit Short Speedwick : 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;
  finalCasual Boutique London Times Dress winter Fpwqx71 String body;

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