Add addDragStartListener flag to enable custom drag handles with ReorderableGridDragStartListener

[shebnik]

This PR introduces a new boolean property, addDragStartListener. When set to false, the ReorderableGridDragStartListener will not be injected, allowing to listen to item builder children tap events and wrap own widgets (e.g. a “burger” icon) with ReorderableGridDragStartListener at any desired location inside item builder, which can be used to edit list order.

This closes the issue #132 requesting support for custom drag handles:

“Please provide a way to use ReorderableGridDragStartListener with custom widget, … when by design we want to drag only with specific burger icon instead of full item widget.”

Changes:

• New API

  /// Whether to add a [ReorderableGridDragStartListener] to the reorderable ItemBuilder.
  /// 
  /// Defaults to true.
  /// 
  /// If set to false, the items in ItemBuilder will not respond to pointer down events,
  /// which means they won't be draggable. This can be useful if you still want to
  /// receive item pointer events, and add your custom drag start listener
  /// to the item widget.
  /// 
  /// Example:
  /// ```dart
  /// ReorderableGridDragStartListener(
  ///   index: dragIndex,
  ///   child: const Icon(
  ///     Icons.drag_handle_outlined,
  ///   ),
  /// ),
  /// ```
  final bool addDragStartListener;

• Constructor default:
  Sets addDragStartListener = true to preserve existing behavior.

• reorderableItemBuilder:

  • If addDragStartListener == false, simply returns the item, without ReorderableGridDragStartListener.
  • Otherwise, retains existing logic, whole item is draggable.

Usage Example:

AnimatedReorderableListView(
  items: items,
  addDragStartListener: false, // disable drag listener
  itemBuilder: (context, index) {
    final item = items[index];
    return ListTile(
      title: Text(item.title),
      onTap: () {
        // Handle item tap, if needed
      },
      trailing: ReorderableGridDragStartListener(
        index: index,
        child: Icon(Icons.drag_handle), // custom handle
      ),
    );
  },
  onReorder: (int oldIndex, int newIndex) {
    setState(() {
      final item = items.removeAt(oldIndex);
      items.insert(newIndex, item);
    });
   },
   isSameItem: (a, b) => a.id == b.id,
);

Local Testing / Preview

To try out this PR, point your pubspec.yaml at the Git branch:

dependency_overrides:
  animated_reorderable_list:
    git:
      url: https://github.com/shebnik/animated_reorderable_list.git
      ref: fix-item-tap