CollectionView

Introduction

The CollectionView widget is a powerful, type-safe wrapper for displaying lists of data in your Nylo Website projects. It simplifies working with ListView, ListView.separated, and grid layouts while providing built-in support for:

• Async data loading with automatic loading states
• Pull-to-refresh and pagination
• Type-safe item builders with position helpers
• Empty state handling
• Data sorting and transformation

Basic Usage

Here's a simple example displaying a list of items:

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: CollectionView<String>(
      data: () => ['Item 1', 'Item 2', 'Item 3'],
      builder: (context, item) {
        return ListTile(
          title: Text(item.data),
        );
      },
    ),
  );
}

With async data from an API:

CollectionView<Todo>(
  data: () async {
    return await api<ApiService>((request) =>
      request.get('https://jsonplaceholder.typicode.com/todos')
    );
  },
  builder: (context, item) {
    return ListTile(
      title: Text(item.data.title),
      subtitle: Text(item.data.completed ? 'Done' : 'Pending'),
    );
  },
)

CollectionItem Helper

The builder callback receives a CollectionItem<T> object that wraps your data with useful position helpers:

CollectionView<String>(
  data: () => ['First', 'Second', 'Third', 'Fourth'],
  builder: (context, item) {
    return Container(
      color: item.isEven ? Colors.grey[100] : Colors.white,
      child: ListTile(
        title: Text('${item.data} (index: ${item.index})'),
        subtitle: Text('Progress: ${(item.progress * 100).toInt()}%'),
      ),
    );
  },
)

CollectionItem Properties

CollectionItem Methods

CollectionView

The default constructor creates a standard list view:

CollectionView<Map<String, dynamic>>(
  data: () async {
    return [
      {"title": "Clean Room"},
      {"title": "Go shopping"},
      {"title": "Buy groceries"},
    ];
  },
  builder: (context, item) {
    return ListTile(title: Text(item.data['title']));
  },
  spacing: 8.0, // Add spacing between items
  padding: EdgeInsets.all(16),
)

CollectionView.separated

Creates a list with separators between items:

CollectionView<User>.separated(
  data: () async => await fetchUsers(),
  builder: (context, item) {
    return ListTile(
      title: Text(item.data.name),
      subtitle: Text(item.data.email),
    );
  },
  separatorBuilder: (context, index) {
    return Divider(height: 1);
  },
)

CollectionView.grid

Creates a grid layout using staggered grid:

CollectionView<Product>.grid(
  data: () async => await fetchProducts(),
  builder: (context, item) {
    return ProductCard(product: item.data);
  },
  crossAxisCount: 2,
  mainAxisSpacing: 8.0,
  crossAxisSpacing: 8.0,
  padding: EdgeInsets.all(16),
)

CollectionView.pullable

Creates a list with pull-to-refresh and infinite scroll pagination:

CollectionView<Post>.pullable(
  data: (int iteration) async {
    // iteration starts at 1 and increments on each load
    return await api<ApiService>((request) =>
      request.get('/posts?page=$iteration')
    );
  },
  builder: (context, item) {
    return PostCard(post: item.data);
  },
  onRefresh: () {
    print('List was refreshed!');
  },
  headerStyle: 'WaterDropHeader', // Pull indicator style
)

Header Styles

The headerStyle parameter accepts:

• 'WaterDropHeader' (default) - Water drop animation
• 'ClassicHeader' - Classic pull indicator
• 'MaterialClassicHeader' - Material design style
• 'WaterDropMaterialHeader' - Material water drop
• 'BezierHeader' - Bezier curve animation

Pagination Callbacks

CollectionView.pullableSeparated

Combines pull-to-refresh with separated list:

CollectionView<Message>.pullableSeparated(
  data: (iteration) async => await fetchMessages(page: iteration),
  builder: (context, item) {
    return MessageTile(message: item.data);
  },
  separatorBuilder: (context, index) => Divider(),
)

CollectionView.pullableGrid

Combines pull-to-refresh with grid layout:

CollectionView<Photo>.pullableGrid(
  data: (iteration) async => await fetchPhotos(page: iteration),
  builder: (context, item) {
    return Image.network(item.data.url);
  },
  crossAxisCount: 3,
  mainAxisSpacing: 4,
  crossAxisSpacing: 4,
)

Loading Styles

Customize the loading indicator using loadingStyle:

// Normal loading with custom widget
CollectionView<Item>(
  data: () async => await fetchItems(),
  builder: (context, item) => ItemTile(item: item.data),
  loadingStyle: LoadingStyle.normal(
    child: Text("Loading items..."),
  ),
)

// Skeletonizer loading effect
CollectionView<User>(
  data: () async => await fetchUsers(),
  builder: (context, item) => UserCard(user: item.data),
  loadingStyle: LoadingStyle.skeletonizer(
    child: UserCard(user: User.placeholder()),
    effect: SkeletonizerEffect.shimmer,
  ),
)

Empty State

Display a custom widget when the list is empty:

CollectionView<Item>(
  data: () async => await fetchItems(),
  builder: (context, item) => ItemTile(item: item.data),
  empty: Center(
    child: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Icon(Icons.inbox, size: 64, color: Colors.grey),
        SizedBox(height: 16),
        Text('No items found'),
      ],
    ),
  ),
)

Sorting and Transforming Data

Sorting

Sort items before display:

CollectionView<Task>(
  data: () async => await fetchTasks(),
  builder: (context, item) => TaskTile(task: item.data),
  sort: (List<Task> items) {
    items.sort((a, b) => a.dueDate.compareTo(b.dueDate));
    return items;
  },
)

Transform

Transform the data after loading:

CollectionView<User>(
  data: () async => await fetchUsers(),
  builder: (context, item) => UserTile(user: item.data),
  transform: (List<User> users) {
    // Filter to only active users
    return users.where((u) => u.isActive).toList();
  },
)

Updating the State

You can update or reset a CollectionView by giving it a stateName:

CollectionView<Todo>(
  stateName: "my_todo_list",
  data: () async => await fetchTodos(),
  builder: (context, item) => TodoTile(todo: item.data),
)

Reset the list

// Resets and reloads data from scratch
CollectionView.stateReset("my_todo_list");

Remove an item

// Remove item at index 2
CollectionView.removeFromIndex("my_todo_list", 2);

Trigger a general update

// Using the global updateState helper
updateState("my_todo_list");

Parameters Reference

Common Parameters

Pullable-Specific Parameters

Grid-Specific Parameters

ListView Parameters

All standard ListView parameters are also supported: scrollDirection, reverse, controller, physics, shrinkWrap, padding, cacheExtent, and more.