Building an Optimized Infinite Scroll with Riverpod and Flutter

Infinite scrolling is a common design pattern in modern mobile apps, allowing users to continuously load more content as they scroll through a page. This article will introduce a Flutter example that uses Riverpod and the infinite_scroll_pagination package to create an efficient and user-friendly infinite scroll pagination feature. We’ll also discuss optimization techniques to avoid unnecessary list rebuilds, enhancing app performance.

Project Overview

The primary goal of this sample project is to demonstrate how to implement paginated loading with Riverpod while optimizing the list's performance by preventing the entire list from rebuilding when the list state changes or when updating individual items.

Project Features

• Simple and efficient state management with Riverpod.
• Supports infinite scroll pagination for a seamless user experience.
• Optimized to avoid unnecessary list rebuilds when updating specific items.
• Error handling mechanism allowing users to retry loading on failure.

Key Dependencies

This project uses the following main dependencies:

• Flutter: 3.0.0 or higher
• Riverpod: ^2.0.0

Getting Started

1. First, clone the project to your local machine:

   git clone https://github.com/lhjandroid/riverpod_infinite_scroll_page.git
   cd riverpod_infinite_scroll_page
   
   2.	Install dependencies:
   

flutter pub get

3.	Run the project:

flutter run

4.	You can also use the package directly:

dependencies: riverpod_infinite_scroll_page: ^0.0.1

Project Structure

The core project files include:

•	lib/main.dart: The application entry point.
•	lib/models/: Defines data models.
•	lib/providers/: Defines Riverpod providers and the pagination state manager.
•	lib/widgets/: Defines reusable UI components.

Implementing Pagination with Riverpod

In the providers/ directory, we define a pagination provider (paging_provider.dart) and use Riverpod to manage pagination state and data fetching. This allows the app to load additional data as needed and manage different states such as loading, successful loading, or failed loading.

Key states include:

•	isLoading: Indicates if the app is currently loading.
•	hasError: Indicates if an error occurred during loading.
•	hasMoreData: Indicates if more data is available to load.

These states allow flexible control over data loading, error handling, and loading additional data.

Implementing Infinite Scrolling

In the main screen under screens/, we use PagedListView to create a scrollable list. When the user reaches the bottom of the list, a request to load more data is triggered automatically.

class _TestPageState extends ConsumerState<TestPage> {
  // Unique key for each page, named after the class here
  final String pageKey = '_TestPageState';

  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: PagedListView<String, PagingItem>(
        pagingControllerProvider: pagingControllerProvider(pageKey), // Paging controller for data handling, globally defined
        builderDelegate: itemRegister(), // Register list items to allow different item types in one list
        pagingDataController: TestPageNetWorkController(), // Manages network data for the page
        statusBuilderDelegate: statusBuilder(), // Handles multi-status view, allowing custom loading, error styles, etc.
      ),
      floatingActionButton: FloatingActionButton(onPressed: () {
        final pagingController =
            ref.read(pagingControllerProvider(pageKey).notifier);
        pagingController.updateItemAt(8, TestItem('11111')); // Updates specific item without refreshing the whole list
      }),
    );
  }

  PagedChildStatusBuilderDelegate<PagingItem> statusBuilder() {
    return PagedChildStatusBuilderDelegate(
      newPageErrorIndicatorBuilder: (context, retryCallback) {
        return GestureDetector(
          onTap: retryCallback,
          child: const SizedBox(
            height: 40,
            child: Center(child: Text('error')),
          ),
        );
      },
    );
  }

  MultiItemChildBuilderDelegate itemRegister() {
    return MultiItemChildBuilderDelegate(
      pageKey,
      pagingItemRegister: PagingItemRegister(
        itemRegister: {
          TestItem: buildTestItem, // All list items inherit from PagingItem; if the list has different styles, define a build method for each item type
        },
      ),
    );
  }

  Widget buildTestItem<T extends PagingItem>(
      BuildContext context, T data, int index) {
    print('buildTestItem $index');
    final testItem = data as TestItem; // Assuming TestItem is the specific type here
    return Text('item $index name${testItem.name}');
  }
}

Avoiding Unnecessary Rebuilds

A common performance issue is that the entire list may rebuild when the list state changes, affecting scroll smoothness. To solve this, we optimize the implementation to trigger item rebuilds only when specific items need updating, preventing the entire list from refreshing. This is especially important for large lists, significantly improving performance and reducing lag.

Error Handling

The project also includes basic error handling. If data loading fails, an error message appears along with a “Retry” button, allowing users to reload data.

Customization

1.	Replace the data source API in paging_provider.dart with your own.
2.	Define your own data models in the models/ directory according to your data structure. Each item should inherit from PagingItem, with the specific data type assigned a type in the model.

PagedChildStatusBuilderDelegate allows you to define custom layout styles for different status views.

Demo

Run the project on an emulator or device to see a scrollable list with infinite scrolling. When you reach the bottom of the list, more data loads automatically, providing a smooth scrolling experience.

Conclusion

Using Riverpod and infinite_scroll_pagination, we can easily implement an efficient infinite scroll pagination feature while optimizing the rebuild mechanism to enhance app performance. Feel free to expand and customize this project according to your needs!

Project Repository Package on Pub.dev

We hope this article helps developers better understand and implement optimized infinite scrolling! If you have any questions or suggestions, feel free to submit an issue or PR on the project’s GitHub repository.

Happy coding! 🎉