Drag and Drop Recipe

Sometimes, users need to arrange the order of some collection. The APIs mentioned here should assist you in developing such a feature.

Make your adapter mutable

DpadDragHelper requires a DpadDragHelper.DragAdapter<T> that exposes the mutable collection backing the adapter contents. This allows DpadDragHelper to change the order of the elements for you automatically.

You just need to implement DpadDragHelper.DragAdapter<T> for this step:

class ExampleAdapter(
    private val adapterConfig: AdapterConfig
) : RecyclerView.Adapter<RecyclerView.ViewHolder>(), 
    DpadDragHelper.DragAdapter<Int> {

    private val items = ArrayList<Int>()

    override fun getMutableItems(): MutableList<Int> = items

Create a DpadDragHelper

Now that you have a DragAdapter setup, just create a DpadDragHelper like so:

private val adapter = ExampleAdapter()
private val dragHelper = DpadDragHelper(
    adapter = dragAdapter,
    callback = object : DpadDragHelper.DragCallback {
        override fun onDragStarted(viewHolder: RecyclerView.ViewHolder) {
            // ViewHolder is now being dragged
        }
        override fun onDragStopped(fromUser: Boolean) {
            // Dragging was cancelled either by user or programmatically
        }
    }
)

Then attach it to your DpadRecyclerView:

dragHelper.attachToRecyclerView(dpadRecyclerView)

Note

This only supports drag and drop for linear and grid layouts with the same number of spans.

Start and stop dragging

Now that DpadDragHelper is setup, you can start dragging by using:

dragHelper.startDrag(position = 0)

If the position passed in the method above is not currently selected, a selection will be triggered.

To cancel dragging for any reason, use:

dragHelper.stopDrag()

Note

Users can also stop dragging by pressing the following keys: KeyEvent.KEYCODE_DPAD_CENTER, KeyEvent.KEYCODE_ENTER. These are customizable in the constructor of DpadDragHelper