Option to disable reordering for specific items

[tomasbaran]

Is there an existing issue for this?

• [X] I have searched the existing issues
• [X] I have read the guide to filing a bug

Use case

My specific use case is to create a photo upload screen that allows a user to upload a set number of images, building up a grid as they add photos. I would like the last item in the grid to be a "+" button used for adding the next image, but i do not want them to be able to reorder this item.

Another case is having a todo list: ReorderableListView where the last item would be "COMPLETED" todoes which should not be draggable.

There are some workaround, so no other item can reorder that one but basically none that I know of is able to get rid of this reordering effect:

https://github.com/flutter/flutter/assets/25743901/41126664-243c-410e-8706-e764e949239d

Proposal

Add an option: enableReoreding' so it'd be another option that'd go next to thekey` parameter.

[tomasbaran]

You can find partial workarounds here but again no full workaround found: https://github.com/hanshengchiu/reorderables/issues/89#:%7E:text=movable%20widgets%20in%3A-,GestureDetector(%0A%20%20%20%20%20%20onLongPress%3A%20()%20%7B%7D%2C%20//%20Override%20onLongPress%20to%20make%20item%20unmovable.%0A%20%20%20%20%20%20child%3A%20...%0A),-6

[navaronbracke]

You can disable the drag handle for the last item (by not wrapping the widget in a ReorderableDragStartListener), but that does not prevent the last item from moving away from the drag proxy item, even though it does not participate in being draggable itself.

However, you could use a SliverReorderableList that contains the reorderable items, and add the last item outside of that list, below the SliverReorderableList in the widget tree.

[tomasbaran]

If the item that should not be draggable is the first one or the last one, the parameter header or footer should be used. This may actually solve the issue overall.

[plammens]

I have use cases where the item that should not be draggable is neither at the start or the end. For example, in an agenda view, I have a divider that indicates the current time right now, separating past events from future events.

[jlambright]

I'm in a similar boat to @plammens , and need to be able to add "Add Here" widgets as separators to each list item. Obviously, I don't want those to be draggable. I could nerf dragging on those separator widgets...but that seems like a bad bandaid.

  void onReorder(int oldIndex, int newIndex) {
    // Only allow reordering if both indices correspond to element
    if (oldIndex % 2 == 0 && newIndex % 2 == 0) {
      // Reordering objectives
      int oldElementIndex = oldIndex ~/ 2;
      int newElementIndex = newIndex ~/ 2;

      insertElement(
          newElementIndex, reordableList.removeAt(oldElementIndex));
    }
  }

This is far from perfect.