RecyclerView and background requests with large collection of items

Question

I have a RecyclerView with a large collection bound to it, say 500+ items. When onBindViewHolder is called I make a async HTTP request to load some data.

But when I scroll really fast down the list, how do i cancel the requests for all items that are no longer in view? I am seeing 100's of requests start in the background because of how RecyclerView loads, i think onBindViewHolder is called for every item i scroll past?

I was thinking to kick off a request in onBindViewHolder that waits 500ms and if the item bound to it is still in view / still the same then starts the async request. Would this work? If so then how do i check if the item is in view still from within the Adapter ?

What's the correct way to solve this problem?

Answer 1

You can make a OnScrollListener for RecyclerView:

 public void onScrollStateChanged(AbsListView view, int scrollState) {
    if (scrollState == SCROLL_STATE_IDLE){
        int firstVisibleItem = view.getFirstVisiblePosition();
        int lastVisiblePosition = view.getLastVisiblePosition();

        //call request from firstVisibleItem to lastVisiblePosition 

    }
}