What is the recommended way to launch a DialogFragment from a ViewModel?

Question

I have a list objects in a Recyclerview. When long-pressing an item I want to show a dialog with data from the item clicked.

The Recyclerview

Answer 1

Conceptually a ViewModel strikes me as the wrong place to launch a Dialog from. To do it more cleanly I would pass the RecyclerView.ViewHolder into the layout, and have a method on the ViewHolder that triggers a custom listener on your RecyclerView.Adapter. Then whoever subscribes to that listener (Activity/Fragment) can launch the Dialog. May seem a little roundabout, but I don't think a ViewModel of a list item should have knowledge or control of its environment.

Here is an example. This is a general pattern for handling RecyclerView item clicks with data binding and a ViewModel. This is not a complete example, just the code to highlight this specific pattern.

Layout:

Adapter:

class MyAdapter extends RecyclerView.Adapter {
    public interface SelectionListener {
        void onSelectionChanged(int newPosition, ViewModel viewModel);
    }

    private @NonNull WeakReference selectionListener =
            new WeakReference<>(null);

    public void setSelectionListener(@Nullable SelectionListener listener) {
        selectionListener = new WeakReference<>(listener);
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        ViewHolder(ViewBinding binding) {
            super(binding.getRoot());

            binding.setViewHolder(this);
            binding.setViewModel(new ViewModel());
        }

        public void onClick(ViewModel viewModel) {
            SelectionListener listener = selectionListener.get();
            if (listener != null) {
                listener.onSelectionChanged(getAdapterPosition(), viewModel);
            }
        }
    }
}