如何在Recyclerview中加载更多JSON数据

Question

I have a endless Recyclerview with a onScrollListener implemented that tells me when I reach the bottom of my Recyclerview. All is set and done. But the thing is I'm missing the most important part; it's how do I load more data in my adapter? Do I call another volley request for the next page of my JSON data? The API I'm using has a 100 objects limit

mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            visibleItemCount = mLayoutManager.getChildCount();
            totalItemCount = mLayoutManager.getItemCount();
            pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();

            if (loading){
                if ( (visibleItemCount+pastVisiblesItems) >= totalItemCount ){
                    loading = false;
                    Toast.makeText(getActivity(), "Last Item", Toast.LENGTH_LONG).show();
                }
            }
        }
    });

Thanks!

Answer 1

When you detect that you've reached the end of your current dataset, you should call whatever logic you need to fetch more data. For example, in a paged request you should keep track of whatever pages you've already successfully loaded, and request new data.

After successfully loading the new data, you should add the models to your data source, then notify the adapter that its dataset has changed, which will update what the user sees on the screen. You want something similar to the code below:

private int pageNo = 0;

private List<Model> getPagedData(int page) {
    // TODO retrieve JSON from server
    // e.g. GET http://fakewebsite.com?page=2

    if (success) {
        pageNo++;
    }
    else {
        // TODO handle error
    }
}

modelList.addAll(getPagedData(pageNo)); // add newly retrieved data
adapter.notifyDataSetChanged(); // tells RecyclerView to bind new models