Android RecyclerView Adapter: notifyItemInserted and notifyItemMoved at index 0 not working

Question

I have a RecyclerView with a horizontal linear layout manager declared like this:

RecyclerView graph = (RecyclerView) findViewById(R.id.graph);

RecyclerView.LayoutManager classManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
graph.setLayoutManager(classManager);
graph.addItemDecoration(new ComponentDecorator(this)); //Just sets a margin around each item

I have a method which inserts a placeholder view into the RecyclerView like this:

private void insertPlaceholder(int index) {
    int placeholderIndex = getIndexOfPlaceholder(); //returns index of existing placeholder, -1 if none

    //No need to do anything
    if(placeholderIndex == index)
        return;

    if(placeholderIndex == -1) {
        ClassGraphItem placeholder = new ClassGraphItem();
        placeholder.setType(ClassGraphItem.PLACEHOLDER);

        mItems.add(index, placeholder);
        Print.log("notify item inserted at index", index);
        notifyItemInserted(index);
    }
    else {
        ClassGraphItem placeholder = mItems.get(placeholderIndex);
        mItems.remove(placeholderIndex);
        mItems.add(index, placeholder);

        notifyItemMoved(placeholderIndex, index);
    }
}

The placeholder is just an invisible view which simulates a space opening between two existing views:

private class PlaceholderViewHolder extends RecyclerView.ViewHolder {

    public PlaceholderViewHolder(View itemView) {
        super(itemView);

        ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(mComponentWidth, 1);
        itemView.setLayoutParams(params);

        itemView.setVisibility(View.INVISIBLE);
    }

}

When the inserted index is > 0, it works perfectly. However at index 0, either inserting a placeholder, or moving an existing placeholder to the 0 index does not work, specifically the RecyclerView doesn't animate to show the new item inserted at index 0. If I used notifyDataSetChanged() it does work. however that doesn't animate and isn't the effect I'm looking for. This seems like a bug to me, but I wanted to make sure there wasn't something else that was causing this issue.

I'm on the latest version of the recyclerview support library (24.2.1). Thanks!

Answer 1

I removed recycler.setHasFixedSize(true); and now it works. I have no idea why this would be related though.