Introduction

Infinite scrolling is a common UX pattern in modern mobile applications: lists grow as the user approaches the end, avoiding pagination UI and keeping engagement high. In Flutter, handling infinite scrolling correctly requires coordination between the UI, scroll state, and the backend pagination contract. This tutorial walks through a pragmatic approach to implement infinite scrolling in Flutter for robust mobile development apps.

Choosing A Pagination Strategy

Start by deciding the pagination model your backend exposes: offset-based (page/limit or start/limit) or cursor-based (next token, cursor, or timestamp). Cursor-based pagination is generally more reliable for large or frequently changing datasets because it avoids skipping or duplicating items when the underlying data mutates. Offset-based pagination is easier to implement but can produce inconsistent results if the dataset changes between requests.

Design your data contract clearly: page size, response shape (items + nextCursor or totalItems), and error semantics. Keep page size configurable in your client to tune performance and perceived latency in mobile development environments.

Backend Contract And Page Models

Model your page response in Dart so your UI code is decoupled from the raw API. Use lightweight models and return a simple wrapper that contains the list of items and either a nextCursor or a boolean hasMore.

Example Page model:

class Page<T> {
  final List<T> items;
  final String? nextCursor;
  Page({required this.items, this.nextCursor});
}

Implement a repository method that accepts a cursor or page number and returns Page. Keep networking concerns (HTTP client, headers, retry) inside the repository so widgets stay focused on display and state.

Implementing Scroll Listener And Loading State

Use a ScrollController attached to a ListView (or CustomScrollView) and listen for position changes. Trigger a new fetch when the scroll position reaches a threshold from the max scroll extent. Manage these state variables: items list, loading flag, nextCursor (or page index), and an error state for retry.

Keep a guard so you never issue concurrent page requests: if loading is true or nextCursor indicates no more data, do nothing.

Example StatefulWidget listener:

final _controller = ScrollController();
@override
void initState() {
  super.initState();
  _controller.addListener(() {
    if (_controller.position.pixels >= _controller.position.maxScrollExtent - 200) {
      _fetchNextPage();
    }
  });
}

In _fetchNextPage, set loading = true, call repository.fetch(cursor), append items, update nextCursor, set loading = false, and call setState. On error, set an error flag and allow the user to retry.

Performance And UX Considerations

• Batch Size: Tune the page size to balance number of network calls vs. payload size. On mobile networks, smaller pages reduce perceived latency; for Wi-Fi, larger pages may be fine.

• Preload Threshold: Use a threshold (e.g., 150–300 px) so the next page loads before the user reaches the end. This hides loading latency and prevents jank.

• Placeholders And Shimmers: Instead of freezing the UI, show a loading tile or shimmer where new rows will appear. This signals progress and keeps the list stable.

• Deduplication: If your API can return overlapping items (cursor drift), deduplicate by id before appending to the list.

• Error Handling: Show inline retry controls rather than modal dialogs. Network errors on mobile are frequent; allow quick retry without losing scroll position.

• Dispose Controller: Remember to dispose ScrollController in dispose() to avoid leaks.

Additional mobile development tips: avoid rebuilding the entire list when appending by using ListView.builder and only updating the underlying data; leverage const widgets where possible.

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Conclusion

Implementing robust infinite scrolling in Flutter hinges on a clear pagination contract, careful scroll listening, and conservative state management. Choose a pagination strategy appropriate for your backend, encapsulate fetch logic in a repository, and guard against concurrent requests and duplicates. With tuned thresholds, proper UX placeholders, and conservative page sizes, infinite scrolling will feel responsive and native on both Android and iOS devices. This pattern scales well in Flutter and is essential for modern mobile development projects.