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January 6, 2021 08:40
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import android.util.Log; | |
import android.widget.Toast; | |
import androidx.recyclerview.widget.GridLayoutManager; | |
import androidx.recyclerview.widget.LinearLayoutManager; | |
import androidx.recyclerview.widget.RecyclerView; | |
import androidx.recyclerview.widget.StaggeredGridLayoutManager; | |
/** | |
* Custom implementation for OnScrollListener to know more items are needed to load when the list reaches at its end. | |
* <p> | |
* Gist taken from: https://gist.github.com/nesquena/d09dc68ff07e845cc622 | |
* <p> | |
* Created by Rafay Ali on 4/26/2016. | |
*/ | |
public abstract class EndlessRecyclerViewScrollListener extends RecyclerView.OnScrollListener { | |
// The minimum amount of items to have below your active scroll position | |
// before loading more. | |
private int visibleThreshold = 7; | |
// The active 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(); | |
} | |
private 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; | |
} | |
@Override | |
public void onScrollStateChanged(RecyclerView recyclerView, int newState) { | |
super.onScrollStateChanged(recyclerView, newState); | |
// if (!recyclerView.canScrollVertically(1)) { | |
// Toast.makeText(this, "Last", Toast.LENGTH_LONG).show(); | |
Log.d("scroll changed", newState+""); | |
// } | |
} | |
// 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) { | |
Log.d("on scroll changed dy", dy+""); | |
int lastVisibleItemPosition = 0; | |
int totalItemCount = mLayoutManager.getItemCount(); | |
int visibleItemCount = mLayoutManager.getChildCount(); | |
Log.d("visibleItemCount", visibleItemCount+""); | |
if (mLayoutManager instanceof StaggeredGridLayoutManager) { | |
int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastCompletelyVisibleItemPositions(null); | |
// get maximum element within the list | |
lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions); | |
} else if (mLayoutManager instanceof LinearLayoutManager) { | |
lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition(); | |
} else if (mLayoutManager instanceof GridLayoutManager) { | |
lastVisibleItemPosition = ((GridLayoutManager) 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 active 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); | |
loading = true; | |
} | |
} | |
// Defines the process for actually loading more data based on page | |
public abstract void onLoadMore(int page, int totalItemsCount); | |
} |
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