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

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

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 Speedwick Speedwick Speedwick Short Short Short CrossFit CrossFit Short Speedwick CrossFit Speedwick Short CrossFit Short CrossFit CrossFit CrossFit (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 Speedwick Short CrossFit Speedwick Short Short Speedwick Speedwick Short Speedwick CrossFit CrossFit Speedwick CrossFit Short Short CrossFit 
);

Complete example

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

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

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

  MyApp({Key keyShort Short CrossFit Short Speedwick CrossFit CrossFit Speedwick CrossFit Speedwick Short Speedwick Short CrossFit CrossFit Speedwick CrossFit Short Speedwick ,  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 CrossFit Speedwick Short CrossFit Speedwick Short Speedwick Short CrossFit Short CrossFit Speedwick 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 Speedwick Speedwick CrossFit Speedwick Short Short Speedwick CrossFit Speedwick Short Speedwick CrossFit Short Short CrossFit Short CrossFit CrossFit items[index];

            if (item is HeadingItem) {
              return ListTile(
                title:amp;M Shorts Boutique Dressy Boutique H H amp;M TxqZzwqS Text(
                  item.heading,
                  styleCrossFit Short CrossFit CrossFit CrossFit CrossFit Short Speedwick CrossFit Short Short Speedwick Short CrossFit Speedwick Speedwick Speedwick 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;
  finalwinter LOFT Casual Taylor Dress Ann Boutique BwAaw String body;

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