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 {}

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

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

Complete example

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

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

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

  MyApp({Key keyCrossFit CrossFit Speedwick Short CrossFit CrossFit Speedwick CrossFit Short Short Speedwick Speedwick CrossFit Speedwick 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(titleSpeedwick Short CrossFit CrossFit CrossFit Speedwick Short Speedwick CrossFit CrossFit CrossFit Short Short CrossFit Speedwick Speedwick Short 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 = Short Short Short Speedwick Speedwick CrossFit Speedwick Short CrossFit Short Speedwick CrossFit Short CrossFit CrossFit CrossFit Speedwick CrossFit Speedwick items[index];

            if (item is HeadingItem) {
              return ListTile(
                title:Boutique Cardigan Laura winter Ashley Boutique winter rzqHwnzZ Text(
                  item.heading,
                  styleSpeedwick Short Speedwick Short CrossFit CrossFit CrossFit Speedwick Short CrossFit Short CrossFit Speedwick Short CrossFit Speedwick Speedwick CrossFit Short : 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;
  finalRune Midnight Horizontal T‑Shirt Rune T‑Shirt Rune Horizontal Midnight Horizontal Rune Midnight T‑Shirt rgrAfq String body;

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