Develop Reference

How to Initialize pagination variable

I am using one intiger variable.
int page=1;
private void pagination() {
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
/*if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
isScrolling = true;
}*/
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
currentItems = manager.getChildCount();
totalItems = manager.getItemCount();
scrollOutItems = manager.findFirstVisibleItemPosition();
if (isScrolling) {
if (totalItems > previousTotal) {
previousTotal = totalItems;
page++;
isScrolling = false;
}
}
if (!isScrolling && (currentItems + scrollOutItems == totalItems)) {
progressBar.setVisibility(View.VISIBLE);
//page=page+1;
/*new Handler().postDelayed(new Runnable() {
#Override
public void run() {
}
}, 5000);*/
getNext();
progressBar.setVisibility(View.GONE);
isScrolling = true;
Log.v("All Courses", "Page Number: " + page);
}
}
});
}
I want to display all course but using 8 course display and when scroll then next 8 course display. Then i click any course then go to new fragment but i press back button in next fragment for back to course fragment then page variable not initialize 1 value. page variable store next increment value.

you can use following code for pagination, it works well. add your first page data to yourRecycler then set the following addOnScrollListener.
private Integer currentPage = 1;
yourRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
void onScrollStateChanged(RecyclerView recyclerView, Integer newState) {
super.onScrollStateChanged(recyclerView, newState)
if (!recyclerView.canScrollVertically(1)) {
currentPage++;
getNextPage();
}
}
})
and you need to add your new page addition actions in following function:
private void getCurrentPage(){
//add new page data to yourRecycler
}
note: it was kotlin code, I converted to java. it can has missing semicolons etc.

How to implement load more in RecyclerView using volley's POST method?

Could you explain to me how I can load 10 items and then 10 more, using the volleyball library?
I have found some old items, but none of them work, maybe it is because of the time since they are from 4 years ago.

You can go with adding Scrolllistener to RecylcerView:
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if(newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL)
{
isScrolling = true;
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
currentItems = manager.getChildCount();
totalItems = manager.getItemCount();
scrollOutItems = manager.findFirstVisibleItemPosition();
if(isScrolling && (currentItems + scrollOutItems == totalItems))
{
isScrolling = false;
getData();
}
}
});
}
Then you can add a handler to load data's
private void getData(){
progressBar.setVisibility(View.VISIBLE);
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
for (int i=0; i<5;i++){
list.add(Math.floor(Math.random()*100) + "");
adapter.notifyDataSetChanged();
progressBar.setVisibility(View.GONE);
}
}
},5000);
}

Calling a function in Viewholder when item selected using SnapHelper

I have a horizontal Recycler view implemented with SnapHelper to get a carousal effect. In my ViewHolder I have a function to animate the views inside Recycler item. So whenever an item is scrolled to center (selected) in SnapHelper I need to start the animation. I have tried following code but its not working. Sometimes I am getting viewholder as null.
widgetScrollView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(final RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_SETTLING) {
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
int pos = ((LinearLayoutManager) widgetScrollView.getLayoutManager()).findFirstCompletelyVisibleItemPosition();
ResultTallyAdapter.ViewHolder viewHolder = (ResultTallyAdapter.ViewHolder) recyclerView.findViewHolderForAdapterPosition(pos);
viewHolder.startAnimation(MainActivity.this, pos);
}
}, 1000);
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
}
});

I was trying same thing like you. But code is different. I use SnapHelper to find current view and get position from this view and start operation on adapter by this position. You can get idea following code, may help you
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(#NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
synchronized (this) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
//calculatePositionAndScroll(recyclerView);
View view = snapHelper.findSnapView(recyclerView.getLayoutManager());
if (view != null) {
int pos = recyclerView.getLayoutManager().getPosition(view);
Log.d("RecyclerViewTest", "position: " + pos + " item: " + itemList.get(pos).getName());
makeSelectedItem(pos); // do your stuff on this view
// adapter.notifyDataSetChanged();
}
}
}
}
#Override
public void onScrolled(#NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
}
});

Recyclerview indicates that reaches the last item

I have a recycleView that I need to observe when the last item is reached but I have notice the it always indicate that I reached the last item even if I haven't scrolled yet.
My code for setting up the recycler:
newsRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
newsRecyclerView.setFocusable(false);
newsRecyclerView.setNestedScrollingEnabled(false);
newsAdapter = new NewsAdapter(getContext(), newsDetails, categoryNumber);
newsRecyclerView.setAdapter(newsAdapter);
layoutManager = new LinearLayoutManager(getContext(), LinearLayoutManager.VERTICAL, false);
My xml code is:
<android.support.v7.widget.RecyclerView
android:id="#+id/news_recycler_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="4dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/news_top_stories_title_text_view" />

This is my code that I put in my Util, and use anywhere.
Util.setRecyclerViewLastPositionListner(rv, linearLayoutManager , new UtilitiesV2.OnLastPositionReached() {
#Override
public void onReached() {
// last position reached
}
});
Put this in Util.
private boolean userScrolled = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;
public interface OnLastPositionReached {
void onReached();
}
public void setRecyclerViewLastPositionListner(RecyclerView rvBooksMockTest, final LinearLayoutManager mLayoutManager, final OnLastPositionReached onLastPositionReached) {
rvBooksMockTest.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
userScrolled = true;
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// Here get the child count, item count and visibleitems
// from layout manager
visibleItemCount = mLayoutManager.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
// Now check if userScrolled is true and also check if
// the item is end then update recycler view and set
// userScrolled to false
if (userScrolled && (visibleItemCount + pastVisiblesItems) == totalItemCount) {
userScrolled = false;
if (onLastPositionReached != null) onLastPositionReached.onReached();
}
}
});
}
Update
According to your requirement, here is NestedScrollView bottom reach listener.
nestedScrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
#Override
public void onScrollChanged() {
if (nestedScrollView != null) {
if (nestedScrollView.getChildAt(0).getBottom() <= (nestedScrollView.getHeight() + nestedScrollView.getScrollY())) {
//scroll view is at bottom
} else {
//scroll view is not at bottom
}
}
}
});

Thanks to Khemraj who give the tip for solution
because I have a recyclerview inside NestedScrollView and coordinator layout as parent for them
I have solved my problem like this:
public Disposable observeNestedScroll(LoadMoreListener listener) {
return RxNestedScrollView.scrollChangeEvents(nestedScrollView)
.subscribe(
viewScrollChangeEvent -> {
NestedScrollView nestedScrollView =(NestedScrollView) viewScrollChangeEvent.view();
if(nestedScrollView.getChildAt(nestedScrollView.getChildCount() - 1) != null) {
if ((viewScrollChangeEvent.scrollY() >= (nestedScrollView.getChildAt(nestedScrollView.getChildCount() - 1).getMeasuredHeight() - nestedScrollView.getMeasuredHeight())) &&
viewScrollChangeEvent.scrollY() > viewScrollChangeEvent.oldScrollY()) {
listener.onLoadMore();
}
}
});
}

I've seen to many responses for this question and I stand that all of them don't give accurate behavior as an outcome. However if you follow this approach I'm positive you'll get the best behavior.
rvCategories is your RecyclerView
categoriesList is the list passed to your adapter
binding.rvCategories.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
val position = (recyclerView.layoutManager as LinearLayoutManager).findLastCompletelyVisibleItemPosition()
if (position + 1 == categoriesList.size) {
// END OF RECYCLERVIEW IS REACHED
} else {
// END OF RECYCLERVIEW IS NOT REACHED
}
}
})

Hiding BottomNavigationView from different fragment

my app has 3 fragments that are being inflated from mainActivity with BottomNavigationView. One of the fragments uses RecyclerView and is scrollable, with BottomNavigationView the last item in recyclerView is being covered up. According to Google's guidelines bottomNavigationView should hide on scroll down and show on scroll up. It's easy enough to make it hide from the mainAcitivity but it doesn't work when Im trying to hide it from the other fragment. How do I do this properly?
This code from recyclerView checks for the scroll state:
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (dy > 0) {
//mainActivity.setNavigationVisibility(false);
} else if (dy < 0 ) {
//mainActivity.setNavigationVisibility(true);
}
}
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
});
And should call this method in the mainActivity that hides the bottomNavigationView:
public void setNavigationVisibility(boolean visible) {
if (navigation.isShown() && !visible) {
navigation.setVisibility(View.GONE);
}
else if (!navigation.isShown() && visible){
navigation.setVisibility(View.VISIBLE);
}
}

try this
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
if (dy > 0) {
((MainActivity)getActivity()).setNavigationVisibility(false);
} else if (dy < 0 ) {
((MainActivity)getActivity()).setNavigationVisibility(true);
}
}
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
});
When you use activity method from fragment then you have to create your method public and you can access that method by typecasting.