findLastVisibleItemPosition is returning wrong value if RecyclerView inside NestedScrollView

I have RecyclerView inside NestedScrollView

<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.v7.widget.RecyclerView
android:id="@+id/recycler"
android:layout_width="match_parent"
android:layout_height="match_parent" />

</android.support.v4.widget.NestedScrollView>


I have this problem in big project and in order to find solution for this problem I have created new project without other views.

This is full code of MainActivity

class MainActivity : AppCompatActivity()

var mItems = mutableListOf<String>()
var mAdapter = MyAdapter(mItems)

override fun onCreate(savedInstanceState: Bundle?)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)

recycler.layoutManager = LinearLayoutManager(this)
recycler.adapter = mAdapter

delayedLoadDataIfPossible(100)

recycler.viewTreeObserver.addOnScrollChangedListener
delayedLoadDataIfPossible(100)




private fun delayedLoadDataIfPossible(delay: Long)
Observable.timer(delay, TimeUnit.MILLISECONDS)
.observeOn(AndroidSchedulers.mainThread())
.subscribe
var scrollingReachedEnd = isScrollingReachedEnd()
if (scrollingReachedEnd)
loadData()




private fun isScrollingReachedEnd(): Boolean
val layoutManager = LinearLayoutManager::class.java.cast(recycler.layoutManager)
val totalItemCount = layoutManager.itemCount
val lastVisible = layoutManager.findLastVisibleItemPosition()
return lastVisible + 5 >= totalItemCount


private fun loadData()
Observable.timer(5, TimeUnit.SECONDS)
.observeOn(AndroidSchedulers.mainThread())
.doOnSubscribe progress.visibility = View.VISIBLE
.doFinally progress.visibility = View.GONE
.subscribe
for (i in 1..10)
mItems.add(i.toString())

mAdapter.notifyDataSetChanged()
delayedLoadDataIfPossible(100)







I am using isScrollingReachedEnd method to identify is scrolling reaching end of list. If there are less than 5 visible items in the end, I am trying to load new data.

loadData simulates loading data. It adds 10 items to list and notifies adapter about change.

delayedLoadDataIfPossible method should work after some delay because findLastVisibleItemPosition is returning value before items are added to list. In result it is returning wrong value. For example -1 after adding first 10 items.

My problem: when RecyclerView inside NestedScrollView findLastVisibleItemPosition returning wrong value and data loading can not be stopped even there are enough items. There is no such problem when RecyclerView not inside NestedScrollView.

My question: how to get last visible item position from RecyclerView when it is inside NestedScrollView?

recyclerView.setNestedScrollingEnabled(false);

RecyclerView

RecyclerView.Adapter

getItemViewType()

2 Answers
2

You could try this approach:

This is my code for a ScrollingListener for a NestedScrollingView:

@Override
public void onScrollChange(NestedScrollView v, int scrollX, int scrollY, int oldScrollX, int oldScrollY)

int lastVisibleItemPosition = 0;
int totalItemCount = layoutManager.getItemCount();

if(v.getChildAt(v.getChildCount() - 1) != null)
if (scrollY >= (v.getChildAt(v.getChildCount()-1).getMeasuredHeight() - v.getMeasuredHeight())
&& scrollY > oldScrollY)
if (layoutManager instanceof LinearLayoutManager)
lastVisibleItemPosition = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();


if (totalItemCount < previousTotalItemCount)
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = totalItemCount;
if (totalItemCount == 0)
this.loading = true;



if (loading && (totalItemCount > previousTotalItemCount))
loading = false;
previousTotalItemCount = totalItemCount;


if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount)
currentPage++;
onLoadMore();
loading = true;






Good luck!

If your RecyclerView is inside a NestedScrollView, you need to add recyclerView.setNestedScrollingEnabled(false) to it.

RecyclerView

NestedScrollView

recyclerView.setNestedScrollingEnabled(false)

Also another note (which is unrelated to your question is that you should definitely keep a reference to those RxJava subscriptions and dispose them on Fragment/Adtivity's onStop, since they can cause memory leak issues.

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