infinite_grouped_list

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Infinite Grouped List

Brings together infinite scrolling, group-based item organization, and numerous other enhancements to improve the end-user experience.

Key Features

• Infinite Scrolling: The widget supports loading more data as the user reaches the end of the list. This is essential for handling large datasets without overwhelming the user or their device.

• Grouping of Items: The widget can organize items into groups based on user-defined criteria. This helps to make sense of large amounts of data by breaking it down into manageable chunks.

• Reactive State Management: 🆕 Full support for modern state management patterns like BLoC, Provider, and Riverpod with dedicated reactive constructors that separate event triggering from data listening.

• Customizable Loading and Error States: You can provide custom widgets to be displayed while data is being loaded or if an error occurs. This allows for a seamless, branded experience.

• Pull-to-Refresh: The widget incorporates a pull-to-refresh feature, letting users manually trigger a refresh of the list's content.

• Sticky Group Headers: Headers stick to the top of the list as the user scrolls, making it easier to understand the context of the data they're viewing. Can be changed.

• Group Anchoring: Opt-in jump-to-group support lets you instantly scroll to any group (for example "Today") through the controller without impacting base performance.

Usage

The InfiniteGroupedList offers two usage patterns to fit different architectural approaches:

🔄 Reactive Pattern (Recommended for Modern Apps)

Perfect for apps using BLoC, Provider, Riverpod, or any external state management:

BlocBuilder<ItemsBloc, ItemsState>(
  builder: (context, state) {
    return InfiniteGroupedList<Item, String, String>.reactive(
      // External state from your state management solution
      items: state.items,
      isLoading: state.isLoading,
      hasReachedMax: state.hasReachedMax,
      error: state.error,

      // Event trigger - cleanly separated from data fetching
      onLoadMoreTriggered: () {
        context.read<ItemsBloc>().add(LoadMoreItems());
      },

      // Refresh trigger
      onRefresh: () {
        context.read<ItemsBloc>().add(RefreshItems());
      },

      // UI builders
      itemBuilder: (item) => ListTile(title: Text(item.name)),
      groupBy: (item) => item.category,
      groupCreator: (category) => category,
      groupTitleBuilder: (title, _, __, ___) => Text(title),
    );
  },
)

⚡ Imperative Pattern (Traditional Approach)

For apps that prefer direct data fetching within the widget:

InfiniteGroupedList(
  onLoadMore: (paginationInfo) async {
    // Fetch data directly and return it
    return await apiService.fetchItems(
      page: paginationInfo.page,
      limit: 20,
    );
  },
  itemBuilder: (item) => ListTile(title: Text(item.name)),
  groupBy: (item) => item.category,
  groupCreator: (category) => category,
  groupTitleBuilder: (title, _, __, ___) => Text(title),
)

Key Differences

• Reactive: Event triggering and data listening are completely separated. Your state management handles data fetching, and the widget displays the current state.
• Imperative: The widget directly calls your data fetching function and manages the loading states internally.

PaginationInfo Helper

When using the imperative pattern, PaginationInfo provides pagination context:

• offset: Current item offset for offset-based pagination
• page: Current page number for page-based pagination
• limit: Items per page (configurable via controller)

The InfiniteGroupedList widget is a comprehensive solution for any use case that involves displaying large amounts of data in an organized, easy-to-navigate manner.

Jumping to a Group

Need to anchor the list to a specific group (e.g. "Today")? Enable anchoring on the widget and invoke the new controller helper:

final controller = InfiniteGroupedListController<Transaction, DateTime, String>();

InfiniteGroupedList(
  enableAnchoring: true,
  controller: controller,
  // ... other params
);

// Later, jump to a concrete title or resolve it dynamically with a predicate
// Option A: jump by the exact group title you already know
controller.jumpToGroup(
  title: 'Today',
  alignment: 0.0, // pin the header to the top
);

// Option B: resolve dynamically via predicate (provide predicate *instead* of title)
controller.jumpToGroup(
  predicate: (title, groupBy) => isSameDay(groupBy, DateTime.now()),
  alignment: 0.0,
  loadUntilFound: true, // imperative mode only
  maxRetries: 3,
);

Anchoring is opt-in, so you only incur the tiny bookkeeping cost when you actually need the feature. The optional loadUntilFound flag is available in imperative mode; reactive consumers should trigger their own data loads before retrying the jump. When loadUntilFound is enabled, maxRetries limits the extra page loads attempted and defaults to 3.

Examples

Explore comprehensive examples demonstrating different usage patterns:

• 🆕 Reactive BLoC Example: Complete implementation using reactive pattern with flutter_bloc, including error handling, loading states, and event-driven architecture.

• 🎯 Jump to Group Example: Demonstrates enabling anchoring plus controller.jumpToGroup() to instantly scroll to the "Today" section.

• 📅 Group by Date: Traditional imperative pattern grouping transactions by date with custom group titles.

• 🏷️ Group by Type: Demonstrates grouping items by category/type with different visual treatments.

• 🔲 Grid Layout: Shows how to use the .gridView() constructor for grid-based layouts.

Run the example app to see all patterns in action with an interactive example selection screen.

Git Hook

To block pushes when the package does not analyze or test cleanly, install the repo-local pre-push hook once:

./tool/install_git_hooks.sh

The hook runs:

• fvm flutter analyze
• fvm flutter test

Migration Guide

Version 1.4.0 note: The misspelled seperatorBuilder parameter was removed. Use separatorBuilder instead.

Existing users: If you were not using the misspelled separator parameter, your code continues to work without any further changes.

Moving to reactive pattern:

1. Replace InfiniteGroupedList() with InfiniteGroupedList.reactive()
2. Move your onLoadMore logic to your state management solution
3. Replace the onLoadMore parameter with onLoadMoreTriggered callback
4. Provide external state via items, isLoading, hasReachedMax parameters

The reactive pattern is recommended for new projects using modern state management, while the imperative pattern remains fully supported for simpler use cases.