RecyclerView - changing selected item icon needs two clicks to work

问题

I am working on a mailing app, in which user can send the same mail to multiple contacts. When I open the contacts list I want to be able to click on the user and his profile picture should be replaced with checked icon.

When I click to select a user the icon flickers and it does not change the first time I click on it. Second time I click on it the image still flickers, but then changes to checked, and every next time I click on that user it will flicker but do what I want - become checked/unchecked.

I am using this tutorial as a guide, but it is not documented as good as it should be. Some methods are explained in a single word, other not even mentioned, but appear in the code. I looked for other tutorials, and really found a lot of the same (identical) examples, without going even a bit deeper than the original.

Adapter.java:

@Override
public void onBindViewHolder(final ChooseContactsAdapter.ChooseContactsViewHolder holder, final int position) {
    final Contact contact = contactList.get(position);

    holder.userName.setText(contact.getUserName());

    TextDrawable.IBuilder builder = TextDrawable.builder()
            .beginConfig()
            .withBorder(0)
            .toUpperCase()
            .endConfig()
            .round();

    ColorGenerator generator = ColorGenerator.MATERIAL;
//       generate color based on a key (same key returns the same color), useful for list/grid views
    int color = generator.getColor(contact.getUserId());
    textDrawable = builder.build(contactList.get(position).getUserName().substring(0, 1), color);
    holder.thumbNail.setImageDrawable(textDrawable);
    holder.contactId = contact.getUserId();
    // display profile image
    applyProfilePicture(holder, contact);

    holder.itemView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // toggle selection
            toggleSelection(position);

            // Change background color of the selected items in list view
            holder.itemView.setBackgroundColor(selectedItems.get(position) ? 0x9934B5E4 : Color.TRANSPARENT);

            // check if item still exists
            if (position != RecyclerView.NO_POSITION) {
                Contact contact = contactList.get(position);
                Toast.makeText(v.getContext(), "You clicked " + contact.getUserName(), Toast.LENGTH_SHORT).show();

            }
            // handle icon animation
            applyIconAnimation(holder, position);
        }
    });
}

    private void applyProfilePicture(ChooseContactsViewHolder holder, Contact contact) {
    Picasso.with(context)
            .load(AppConfig.URL_PROFILE_PHOTO + contact.getThumbnailUrl())
            .placeholder(textDrawable)
            .error(textDrawable)
            .transform(new CircleTransform())
            .into(holder.thumbNail);
}

private void applyIconAnimation(ChooseContactsViewHolder holder, int position) {
    if (selectedItems.get(position, false)) {
        holder.iconFront.setVisibility(View.GONE);
        resetIconYAxis(holder.iconBack);
        holder.iconBack.setVisibility(View.VISIBLE);
        holder.iconBack.setAlpha(1);
        if (currentSelectedIndex == position) {
            FlipAnimator.flipView(context, holder.iconBack, holder.iconFront, true);
            resetCurrentIndex();
        }
    } else {
        holder.iconBack.setVisibility(View.GONE);
        resetIconYAxis(holder.iconFront);
        holder.iconFront.setVisibility(View.VISIBLE);
        holder.iconFront.setAlpha(1);
        if ((reverseAllAnimations && animationItemsIndex.get(position, false)) || currentSelectedIndex == position) {
            FlipAnimator.flipView(context, holder.iconBack, holder.iconFront, false);
            resetCurrentIndex();
        }
    }
}

private void toggleSelection(int pos) {
    currentSelectedIndex = pos;
    if (selectedItems.get(pos, false)) {
        selectedItems.delete(pos);
        animationItemsIndex.delete(pos);
    } else {
        selectedItems.put(pos, true);
        animationItemsIndex.put(pos, true);
    }
    notifyItemChanged(pos);
}