Implementing Endless RecyclerView

Question

I want to implement an endless RecyclerView but so far all the implementations and tutorials I have come across describe loading data off a server then loading it or dynamically adding elements using a loop.

In my case, I already have a large ArrayList containing the data I want to display in the RecyclerView.

What I need is to say, display the first 10 items of the array, and on loading more, display the next batch of 10.

Answer 1

try using this class it help me alot :

public abstract class EndlessRecyclerViewScrollListener extends RecyclerView.OnScrollListener {
    // The minimum amount of items to have below your current scroll position
    // before loading more.
    private int visibleThreshold = 5;
    // The current offset index of data you have loaded
    private int currentPage = 0;
    // The total number of items in the dataset after the last load
    private int previousTotalItemCount = 0;
    // True if we are still waiting for the last set of data to load.
    private boolean loading = true;
    // Sets the starting page index
    private int startingPageIndex = 0;

    RecyclerView.LayoutManager mLayoutManager;

    public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
    }

    public EndlessRecyclerViewScrollListener(GridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public EndlessRecyclerViewScrollListener(StaggeredGridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public int getLastVisibleItem(int[] lastVisibleItemPositions) {
        int maxSize = 0;
        for (int i = 0; i < lastVisibleItemPositions.length; i++) {
            if (i == 0) {
                maxSize = lastVisibleItemPositions[i];
            }
            else if (lastVisibleItemPositions[i] > maxSize) {
                maxSize = lastVisibleItemPositions[i];
            }
        }
        return maxSize;
    }

    // This happens many times a second during a scroll, so be wary of the code you place here.
    // We are given a few useful parameters to help us work out if we need to load some more data,
    // but first we check if we are waiting for the previous load to finish.
    @Override
    public void onScrolled(RecyclerView view, int dx, int dy) {
        int lastVisibleItemPosition = 0;
        int totalItemCount = mLayoutManager.getItemCount();

        if (mLayoutManager instanceof StaggeredGridLayoutManager) {
            int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastVisibleItemPositions(null);
            // get maximum element within the list
            lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions);
        } else if (mLayoutManager instanceof GridLayoutManager) {
            lastVisibleItemPosition = ((GridLayoutManager) mLayoutManager).findLastVisibleItemPosition();
        } else if (mLayoutManager instanceof LinearLayoutManager) {
            lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();
        } 

        // If the total item count is zero and the previous isn't, assume the
        // list is invalidated and should be reset back to initial state
        if (totalItemCount < previousTotalItemCount) {
            this.currentPage = this.startingPageIndex;
            this.previousTotalItemCount = totalItemCount;
            if (totalItemCount == 0) {
                this.loading = true;
            }
        }
        // If it’s still loading, we check to see if the dataset count has
        // changed, if so we conclude it has finished loading and update the current page
        // number and total item count.
        if (loading && (totalItemCount > previousTotalItemCount)) {
            loading = false;
            previousTotalItemCount = totalItemCount;
        }

        // If it isn’t currently loading, we check to see if we have breached
        // the visibleThreshold and need to reload more data.
        // If we do need to reload some more data, we execute onLoadMore to fetch the data.
        // threshold should reflect how many total columns there are too
        if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) {
            currentPage++;
            onLoadMore(currentPage, totalItemCount, view);
            loading = true;
        }
    }

    // Call this method whenever performing new searches
    public void resetState() {
        this.currentPage = this.startingPageIndex;
        this.previousTotalItemCount = 0;
        this.loading = true;
    }

    // Defines the process for actually loading more data based on page
    public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view);

}

reference :

• https://gist.github.com/nesquena/d09dc68ff07e845cc622
• https://guides.codepath.com/android/Endless-Scrolling-with-AdapterViews-and-RecyclerView

Answer 2

Try using:

recyclerView.addOnScrollListener (recyclerViewOnScrollListener);

private RecyclerView.OnScrollListener recyclerViewOnScrollListener = new RecyclerView.OnScrollListener () {

   private final String LOG_TAG = "PAGINATION_";
   boolean              isIdle;

   @Override
   public void onScrollStateChanged (RecyclerView recyclerView, int newState) {

       try {
           super.onScrollStateChanged (recyclerView, newState);
           isIdle = (newState == RecyclerView.SCROLL_STATE_IDLE);
       }
       catch (Exception e) {
           e.printStackTrace ();
       }
   }

   @Override
   public void onScrolled (RecyclerView recyclerView, int dx, int dy) {

       firstVisibleItemPosition = layoutManager.findFirstVisibleItemPosition ();

                   super.onScrolled (recyclerView, dx, dy);

                   if (!isIdle dy > 0) {

                       int totalItems = yourList.size()();

                       totalItemCount = layoutManager.getItemCount ();
                       visibleItemCount = layoutManager.getChildCount ();

                       Log.i (LOG_TAG, "Max: " + totalItems + ", Total: " + totalItemCount + ", Previous Total: " + previousTotal + ", Visible: " + visibleItemCount + ", First: " + firstVisibleItemPosition);

                       if (isLoading) {
                           if (totalItemCount != previousTotal) {
                               isLoading = false;
                               previousTotal = totalItemCount;
                           }
                       }

                       isLastPage = (totalItemCount >= totalItems);

                       Log.i (LOG_TAG, "DETAILS: currentPage: " + currentPage + ", isLoading: " + isLoading + ", isLast: " + isLastPage);
                       if (!isLoading && !isLastPage) {
                           if ((visibleItemCount + firstVisibleItemPosition) >= totalItemCount && firstVisibleItemPosition >= 0 && totalItems >= (currentPage * PAGE_LIMIT) && totalItems > totalItemCount) {
                               if (totalItems > (currentPage * PAGE_LIMIT)) {
                                   currentPage = (totalItemCount / PAGE_LIMIT) + 1;
                                   isLoading = true;
                                   //load more data using currentPage and PAGE_LIMIT
                               }
                           }
                       }
                   }
                   previousTotal = totalItemCount;
               }
               catch (Exception e) {
                   e.printStackTrace ();
               }
           }

       }
   }

};

Answer 3

You can use this Endless Adapter

• It is generic, you give it (You model, Recycler.ViewHolder)
• You can set the adapter either show loading or not.
• Have Listeners to check when loading finished, and when loading starts.

You can check also the sample for more info

Answer 4

This could achieve your goal.

public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener {
    public static String TAG = EndlessRecyclerOnScrollListener.class.getSimpleName();

private int previousTotal = 0; // The total number of items in the dataset after the last load
private boolean loading = true; // True if we are still waiting for the last set of data to load.
private int visibleThreshold = 5; // The minimum amount of items to have below your current scroll position before loading more.
int firstVisibleItem, visibleItemCount, totalItemCount;

private int current_page = 1;

private LinearLayoutManager mLinearLayoutManager;

public EndlessRecyclerOnScrollListener(LinearLayoutManager linearLayoutManager) {
    this.mLinearLayoutManager = linearLayoutManager;
}

@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
    super.onScrolled(recyclerView, dx, dy);

    visibleItemCount = recyclerView.getChildCount();
    totalItemCount = mLinearLayoutManager.getItemCount();
    firstVisibleItem = mLinearLayoutManager.findFirstVisibleItemPosition();

    if (loading) {
        if (totalItemCount > previousTotal) {
            loading = false;
            previousTotal = totalItemCount;
        }
    }
    if (!loading && (totalItemCount - visibleItemCount)
            <= (firstVisibleItem + visibleThreshold)) {
        // End has been reached

        // Do something
        current_page++;

        onLoadMore(current_page);

        loading = true;
    }
}

public abstract void onLoadMore(int current_page);
}

And sample activity

public class SampleActivity extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_sample);

    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.list);
    LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(linearLayoutManager);
    recyclerView.setOnScrollListener(new EndlessRecyclerOnScrollListener(linearLayoutManager) {
        @Override
        public void onLoadMore(int current_page) {
            // do something...
        }
    });
}
}

Edit: See here: Endless Scrolling with AdapterViews