Android/app/src/main/java/com/moiseum/wolnelektury/components/recycler/EndlessRecyclerOnScrollListener.java

   1 package com.moiseum.wolnelektury.components.recycler;
   2
   3 /**
   4  * Created by Piotr Ostrowski on 28.11.2017.
   5  */
   6
   7 import android.support.v7.widget.LinearLayoutManager;
   8 import android.support.v7.widget.RecyclerView;
   9
  10 public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener {
  11
  12         public static String TAG = EndlessRecyclerOnScrollListener.class.getSimpleName();
  13
  14         /**
  15          * The total number of items in the dataset after the last load
  16          */
  17         private int mPreviousTotal = 0;
  18         /**
  19          * True if we are still waiting for the last set of data to load.
  20          */
  21         private boolean mLoading = true;
  22
  23         @Override
  24         public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
  25                 super.onScrolled(recyclerView, dx, dy);
  26
  27                 int visibleItemCount = recyclerView.getChildCount();
  28                 int totalItemCount = recyclerView.getLayoutManager().getItemCount();
  29                 int firstVisibleItem = ((LinearLayoutManager) recyclerView.getLayoutManager()).findFirstVisibleItemPosition();
  30
  31                 if (mLoading) {
  32                         if (totalItemCount > mPreviousTotal) {
  33                                 mLoading = false;
  34                                 mPreviousTotal = totalItemCount;
  35                         }
  36                 }
  37                 int visibleThreshold = 5;
  38                 if (!mLoading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
  39                         // End has been reached
  40                         onLoadMore();
  41                         mLoading = true;
  42                 }
  43         }
  44
  45         public void reset() {
  46                 mPreviousTotal = 0;
  47         }
  48
  49         public abstract void onLoadMore();
  50 }