Drag and Drop

To enable drag and drop functionality, implement the ItemDrag interface for your data model:

data class DragModel(override var itemOrientationDrag: Int = ItemOrientation.ALL) : ItemDrag

Note that if your data model is deserialized using Gson, it will remove all field initialization values. To ensure the value is always returned, you can override the accessor function:

class DragModel() : ItemDrag {
    override var itemOrientationDrag: Int = 0
        get() = ItemOrientation.ALL // Always return this value
}

ItemOrientation

The ItemOrientation class includes configurable drag directions:

Field	Description
ALL	All directions
VERTICAL	Vertical direction
HORIZONTAL	Horizontal direction
LEFT	Left direction
RIGHT	Right direction
UP	Up direction
DOWN	Down direction
NONE	Disabled

Customization

If you want to extend ItemTouchHelper or listen to its events, you can assign a value to the itemTouchHelper variable in the BindingAdapter:

rv.linear().setup {
    addType<Model>(R.layout.item)

    itemTouchHelper = ItemTouchHelper(object : DefaultItemTouchCallback(this) {

        /**
         * Called when the drag action is completed and the finger is released.
         */
        open fun onDrag(
            source: BindingAdapter.BindingViewHolder,
            target: BindingAdapter.BindingViewHolder
        ) {
            // This is called after the drag and drop operation, you can synchronize with the server here
        }

    })

}.models = data

Note that DefaultItemTouchCallback is the default touch event handling in BRV. You can override it or directly use ItemTouchHelper.Callback.

Click and Drag

Directly clicking on an item to start dragging can cause gesture conflicts because both scrolling the list and dragging for sorting require movement gestures. Therefore, it is recommended to initiate dragging from a small icon within the item (dragging the icon will scroll the list).

Here's an example code:

rv.linear().setup {
    addType<DragModel>(R.layout.item_drag)
    onBind {
        findView<View>(R.id.btnDrag).setOnTouchListener { _, event ->
            if (event.action == MotionEvent.ACTION_DOWN) { // Start dragging when the finger is pressed
                itemTouchHelper?.startDrag(this)
            }
            true
        }
    }
}.models = getData()