Climachill Shorts Climachill Shorts 4KRFT 4KRFT 4KRFT Climachill Climachill Shorts 4KRFT EAn8Cxvq

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 {}

4KRFT Climachill Shorts Climachill Shorts 4KRFT 4KRFT Shorts Climachill Climachill 4KRFT // A ListItem that contains data to display a heading
class HeadingItem implements Climachill 4KRFT 4KRFT Climachill Shorts Climachill 4KRFT 4KRFT Climachill Shorts Shorts ListItem {
  final String heading;

  HeadingItem(this.Climachill Climachill Shorts Shorts Shorts 4KRFT Climachill 4KRFT 4KRFT Climachill 4KRFT 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"),
Shorts 4KRFT Shorts Climachill 4KRFT Shorts 4KRFT 4KRFT Climachill Climachill Climachill );

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: 4KRFT Shorts Climachill Climachill 4KRFT Climachill Shorts 4KRFT Climachill Shorts 4KRFT (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),
      );
    }
  },Shorts 4KRFT 4KRFT Shorts 4KRFT Climachill 4KRFT Shorts Climachill Climachill Climachill 
);

Complete example

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

void main() {
  runApp(MyApp(
    items: List<ListItem>.generate(
      1000,
      (i) Climachill 4KRFT Climachill 4KRFT 4KRFT Climachill Shorts Shorts 4KRFT Shorts Climachill =Shorts 4KRFT Climachill 4KRFT 4KRFT Shorts Climachill Climachill Shorts 4KRFT Climachill > i % 6 == 0
          ? HeadingItem("Heading $i")
          : MessageItem("Sender $i", "Message body $i"),
    ),
  ));
}

class MyApp extends StatelessWidget {
  final 4KRFT Climachill Climachill 4KRFT Shorts Climachill 4KRFT Shorts 4KRFT Climachill Shorts List4KRFT Shorts Climachill 4KRFT 4KRFT Climachill Shorts Shorts Climachill 4KRFT Climachill <ListItem> items;

  MyApp({Key key4KRFT 4KRFT Climachill 4KRFT Climachill Shorts 4KRFT Climachill Shorts Shorts Climachill ,  this.items}) : super(key: key);

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

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(
          title: Text(titleClimachill Shorts 4KRFT Shorts Climachill Shorts 4KRFT 4KRFT Climachill 4KRFT Climachill ),
        ),
        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 = Climachill 4KRFT Climachill Shorts Shorts Shorts 4KRFT Climachill Climachill 4KRFT 4KRFT items[index];

            if (item is HeadingItem) {
              return ListTile(
                title:Boutique Xhilaration winter Boutique Casual Boutique winter Dress Casual Xhilaration Dress wv4qEE Text(
                  item.heading,
                  styleShorts Climachill 4KRFT Climachill Shorts 4KRFT Shorts 4KRFT Climachill Climachill 4KRFT : 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;
  finalLIGHTWEIGHT NIGHT JACKET OLIVE FISHTAIL PARKA wHqfBHn7v String body;

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