I have a simple recyclerview with items (tips) and a loading spinner at the bottom.
here's how the item count and item view type methods look:
#Override
public int getItemViewType(int position) {
if (position == getItemCount() - 1) { // last position
return LOADING_FOOTER_VIEW_TYPE;
}
else {
return TIP_VIEW_TYPE;
}
}
#Override
public int getItemCount() {
return tips.size() + 1; // + 1 for the loading footer
}
basically, i just have a loading spinner under all my items.
I create the adapter once like so:
public TipsListAdapter(TipsActivity tipsActivity, ArrayList<Tip> tips) {
this.tipsActivity = tipsActivity;
this.tips = tips;
}
and then once i have fetched additional items, i call add like so:
public void addTips(List<Tip> tips) {
// hide the loading footer temporarily
isAdding = true;
notifyItemChanged(getItemCount() - 1);
// insert the new items
int insertPos = this.tips.size(); // this will basically give us the position of the loading spinner
this.tips.addAll(tips);
notifyItemRangeInserted(insertPos, tips.size());
// allow the loading footer to be shown again
isAdding = false;
notifyItemChanged(getItemCount() - 1);
}
What's odd here is that when i do that, the scroll position goes to the very bottom. It almost seems like it followed the loading spinner. This only happens on the first add (i.e. when there is only the loading spinner showing initally). subsequent adds maintains the proper scroll position (the position where the items were inserted).
This doesn't happen if i change notifyItemRangeInserted() to notifyItemRangeChanged() like so:
public void addTips(List<Tip> tips) {
// hide the loading footer temporarily
isAdding = true;
notifyItemChanged(getItemCount() - 1);
// insert the new items
int insertPos = this.tips.size(); // this will basically give us the position of the loading spinner
this.tips.addAll(tips);
notifyItemRangeChanged(insertPos, tips.size());
// allow the loading footer to be shown again
isAdding = false;
notifyItemChanged(getItemCount() - 1);
}
Nor does it happen if i simply call notifyDataSetChanged() like so:
public void addTips(List<Tip> tips) {
this.tips.addAll(tips);
notifyDataSetChanged();
}
Here's the code for setting the adapter in my Activity:
public void setAdapter(#NonNull ArrayList<Tip> tips) {
if (!tips.isEmpty()) { // won't be empty if restoring state
hideProgressBar();
}
tipsList.setAdapter(new TipsListAdapter(this, tips));
}
public void addTips(List<Tip> tips) {
hideProgressBar();
getAdapter().addTips(tips);
restorePageIfNecessary();
}
private TipsListAdapter getAdapter() {
return (TipsListAdapter) tipsList.getAdapter();
}
Note:
I don't manually set scroll position anywhere.
I call setAdapter() in onResume()
addTips() is called after I fetch items from the server
Let me know if you need any additional parts of my code.
This only happens on the first add (i.e. when there is only the loading spinner showing initally). subsequent adds maintains the proper scroll position (the position where the items were inserted).
RecyclerView has built-in behavior when calling the more-specific dataset change methods (like notifyItemRangeInserted() as opposed to notifyDataSetChanged()) that tries to keep the user looking at "the same thing" as before the operation.
When the data set changes, the first item the user can see is prioritized as the "anchor" to keep the user looking at approximately the same thing. If possible, the RecyclerView will try to keep this "anchor" view visible after the adapter update.
On the very first load, the first item (the only item) is the loading indicator. Therefore, when you load the new tips and update the adapter, this behavior will prioritize keeping the loading indicator on-screen. Since the loading indicator is kept at the end of the list, this will scroll the list to the bottom.
On subsequent loads, the first item is not the loading indicator, and it doesn't move. So the RecyclerView will not appear to scroll, since it doesn't have to do so to keep the "anchor" on-screen.
My recommendation is to check insertPos and see if it is zero. If it is, that means this is the first load, so you should update the adapter by calling notifyDataSetChanged() in order to avoid this anchoring behavior. Otherwise, call notifyItemRangeInserted() as you're currently doing.
Remove the setAdapter code from onResume ASAP as you are setting new TipsListAdapter(this, tips);
Every time a new reference of the adapter is created...make field mAdapter and then set it in onCreate . RecyclerView doesnt remember the scrolled position because everytime a new reference of adapter is being created.. onResume gets called infinitely when activity is in running state..
So either you setAdapter in onCreate using new operator to create reference for adapter or,
in onResume use mAdapter field variable reference..
I have implemented my RecyclerView and even added an onscrolllistener to support infinity scrolling and now I'm stuck with a, hopefully, easy problem: How can I add the newly loaded data to the existing dataset?
My current approach: I create a new array with the length of the existing dataset + the length of the newly loaded data. I System.arraycopy my existing dataset and add the new content with a for-loop.
This works but the list is always reset (scrolls back to the top) and I assume my way to add additional content is overly complicated/wrong, though the tutorials I have looked at seem to pass over this "detail".
Update: I'm currently calling "scrollToPosition" on the UI-Thead after the data has been loaded, but I doubt this is the correct way of doing this or am I wrong?
You shouldn't be adding stuff to your dataset, you will sooner or later run out of memory. What you can do is return a big number (I used Short.MAX_VALUE) item in getItemCount inside your adapter and in the method that requests a view for postion you should do position % list.size();
It is not a truly endless RecyclerView this way, but good enough. I will paste some code tomorrow, I don't have it here now :/
I think you have to add items inside your adapter. Let`s say
class Adapter extends Recycler.Adapter<Recycler.ViewHolder>{
List<YourCustomObject> list;
public Adapter(){
list = new ArrayList<>();
}
public void addItem(YourCustomObject item){
list.add(item);
notifyItemDateSetChanged(); //This method for adapter to notice that list size have been changed
}
// Here your views
}
There is implementation of Your fragment or Activity where you retrieve data from internet.Let` say
class MainActivity extends AppCompactActivity{
Adapter adapter = new Adapter();
List<YourCustomObjects> objects;
public void onCreateView(){
//////// Something yours
}
public void onLoadMore(){
///// Your operation to retrieve data and init it to your list objects
for(YourCustomObject object : objects){
adapter.addItem(object);
}
}
}
I am trying to keep my last scrolled position and populate the adapter with new data but same scrolling position. In my scenerio, I have updating expandable listview every 5 second and updating new items very 5 seconds but with last scrolling position left by user.
I have searched a lot about it and found few solutions but still it is behaving strangly each time I set scrolling position.
I am trying to achieve it with this method:
activity.runOnUiThread(new Runnable()
{
#Override public void run() {
state = list.onSaveInstanceState();
if(settings != null) {
if (mode.equals("Now")) {
info_panel = new esInfoListAdapter(activity, data, expanHash, false, esActivity.lastgrpPosition);
}
else {
info_panel = new esInfoListAdapter(Activity.this, data, tchildData, true, lastgrpPosition);
}
}
list.setAdapter(info_panel);
if(state != null)
list.onRestoreInstanceState(state);
info_panel.notifyDataSetChanged();
}
}
});
So this method gets called just before I updating expandable listview. So in short in every five seconds. I am using Parceable object to save list.onSaveInstanceState(); and then use list.onRestoreInstanceState(state); when updating new data, but the issue is sometimes it works and sometimes not? Am I missing some trick here? Thanks for your help.
I have not yet used ExpandableListView yet but I might. I think you should use combination of methods like getFirstVisiblePosition, getLastVisiblePosition, and getExpandableListPosition. I think getting the groupPosition is sufficient for a user. A link I referenced is ...get index of first/last visible group in an ExpandableListView
How does one refresh the data displayed in RecyclerView (calling notifyDataSetChanged on its adapter) and make sure that the scroll position is reset to exactly where it was?
In case of good ol' ListView all it takes is retrieving getChildAt(0), checking its getTop() and calling setSelectionFromTop with the same exact data afterwards.
It doesn't seem to be possible in case of RecyclerView.
I guess I'm supposed to use its LayoutManager which indeed provides scrollToPositionWithOffset(int position, int offset), but what's the proper way to retrieve the position and the offset?
layoutManager.findFirstVisibleItemPosition() and layoutManager.getChildAt(0).getTop()?
Or is there a more elegant way to get the job done?
I use this one.^_^
// Save state
private Parcelable recyclerViewState;
recyclerViewState = recyclerView.getLayoutManager().onSaveInstanceState();
// Restore state
recyclerView.getLayoutManager().onRestoreInstanceState(recyclerViewState);
It is simpler, hope it will help you!
I have quite similar problem. And I came up with following solution.
Using notifyDataSetChanged is a bad idea. You should be more specific, then RecyclerView will save scroll state for you.
For example, if you only need to refresh, or in other words, you want each view to be rebinded, just do this:
adapter.notifyItemRangeChanged(0, adapter.getItemCount());
EDIT: To restore the exact same apparent position, as in, make it look exactly like it did, we need to do something a bit different (See below how to restore the exact scrollY value):
Save the position and offset like this:
LinearLayoutManager manager = (LinearLayoutManager) mRecycler.getLayoutManager();
int firstItem = manager.findFirstVisibleItemPosition();
View firstItemView = manager.findViewByPosition(firstItem);
float topOffset = firstItemView.getTop();
outState.putInt(ARGS_SCROLL_POS, firstItem);
outState.putFloat(ARGS_SCROLL_OFFSET, topOffset);
And then restore the scroll like this:
LinearLayoutManager manager = (LinearLayoutManager) mRecycler.getLayoutManager();
manager.scrollToPositionWithOffset(mStatePos, (int) mStateOffset);
This restores the list to its exact apparent position. Apparent because it will look the same to the user, but it will not have the same scrollY value (because of possible differences in landscape/portrait layout dimensions).
Note that this only works with LinearLayoutManager.
--- Below how to restore the exact scrollY, which will likely make the list look different ---
Apply an OnScrollListener like so:
private int mScrollY;
private RecyclerView.OnScrollListener mTotalScrollListener = new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
mScrollY += dy;
}
};
This will store the exact scroll position at all times in mScrollY.
Store this variable in your Bundle, and restore it in state restoration to a different variable, we'll call it mStateScrollY.
After state restoration and after your RecyclerView has reset all its data reset the scroll with this:
mRecyclerView.scrollBy(0, mStateScrollY);
That's it.
Beware, that you restore the scroll to a different variable, this is important, because the OnScrollListener will be called with .scrollBy() and subsequently will set mScrollY to the value stored in mStateScrollY. If you do not do this mScrollY will have double the scroll value (because the OnScrollListener works with deltas, not absolute scrolls).
State saving in activities can be achieved like this:
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt(ARGS_SCROLL_Y, mScrollY);
}
And to restore call this in your onCreate():
if(savedState != null){
mStateScrollY = savedState.getInt(ARGS_SCROLL_Y, 0);
}
State saving in fragments works in a similar way, but the actual state saving needs a bit of extra work, but there are plenty of articles dealing with that, so you shouldn't have a problem finding out how, the principles of saving the scrollY and restoring it remain the same.
Keep scroll position by using #DawnYu answer to wrap notifyDataSetChanged() like this:
val recyclerViewState = recyclerView.layoutManager?.onSaveInstanceState()
adapter.notifyDataSetChanged()
recyclerView.layoutManager?.onRestoreInstanceState(recyclerViewState)
Yes you can resolve this issue by making the adapter constructor only one time, I am explaining the coding part here :
if (appointmentListAdapter == null) {
appointmentListAdapter = new AppointmentListAdapter(AppointmentsActivity.this);
appointmentListAdapter.addAppointmentListData(appointmentList);
appointmentListAdapter.setOnStatusChangeListener(onStatusChangeListener);
appointmentRecyclerView.setAdapter(appointmentListAdapter);
} else {
appointmentListAdapter.addAppointmentListData(appointmentList);
appointmentListAdapter.notifyDataSetChanged();
}
Now you can see I have checked the adapter is null or not and only initialize when it is null.
If adapter is not null then I am assured that I have initialized my adapter at least one time.
So I will just add list to adapter and call notifydatasetchanged.
RecyclerView always holds the last position scrolled, therefore you don't have to store last position, just call notifydatasetchanged, recycler view always refresh data without going to top.
Thanks
Happy Coding
The top answer by #DawnYu works, but the recyclerview will first scroll to the top, then go back to the intended scroll position causing a "flicker like" reaction which isn't pleasant.
To refresh the recyclerView, especially after coming from another activity, without flickering, and maintaining the scroll position, you need to do the following.
Ensure you are updating you recycler view using DiffUtil. Read more about that here: https://www.journaldev.com/20873/android-recyclerview-diffutil
Onresume of your activity, or at the point you want to update your activity, load data to your recyclerview. Using the diffUtil, only the updates will be made on the recyclerview while maintaining it position.
Hope this helps.
Here is an option for people who use DataBinding for RecyclerView.
I have var recyclerViewState: Parcelable? in my adapter. And I use a BindingAdapter with a variation of #DawnYu's answer to set and update data in the RecyclerView:
#BindingAdapter("items")
fun setRecyclerViewItems(
recyclerView: RecyclerView,
items: List<RecyclerViewItem>?
) {
var adapter = (recyclerView.adapter as? RecyclerViewAdapter)
if (adapter == null) {
adapter = RecyclerViewAdapter()
recyclerView.adapter = adapter
}
adapter.recyclerViewState = recyclerView.layoutManager?.onSaveInstanceState()
// the main idea is in this call with a lambda. It allows to avoid blinking on data update
adapter.submitList(items.orEmpty()) {
adapter.recyclerViewState?.let {
recyclerView.layoutManager?.onRestoreInstanceState(it)
}
}
}
Finally, the XML part looks like:
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/possible_trips_rv"
android:layout_width="match_parent"
android:layout_height="0dp"
app:items="#{viewState.yourItems}"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"/>
I was making a mistake like this, maybe it will help someone :)
If you use recyclerView.setAdapter every time new data come, it calls the adapter clear() method every time you use it, which causes the recyclerview to refresh and start over. To get rid of this, you need to use adapter.notiftyDatasetChanced().
1- You need to save scroll position like this
rvProduct.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
recyclerViewState = rvProduct.getLayoutManager().onSaveInstanceState(); // save recycleView state
}
});
2- And after you call notifyDataSetChanged then onRestoreInstanceState like this example
productsByBrandAdapter.addData(productCompareList);
productsByBrandAdapter.notifyDataSetChanged();
rvProduct.getLayoutManager().onRestoreInstanceState(recyclerViewState); // restore recycleView state
I have not used Recyclerview but I did it on ListView. Sample code in Recyclerview:
setOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
rowPos = mLayoutManager.findFirstVisibleItemPosition();
It is the listener when user is scrolling. The performance overhead is not significant. And the first visible position is accurate this way.
Create Extention and use it entirely your App, if you are using DiffUtil you don't need to add adapter.notifyDataSetChanged()
fun RecyclerView.reStoreState(){
val recyclerViewState = this.layoutManager?.onSaveInstanceState()
this.layoutManager?.onRestoreInstanceState(recyclerViewState)
}
Then use it like this below
yourRecyclerView.reStoreState()
adapter.submitList(yourData)
yourRecyclerView.adapter = adapter
#BindingAdapter("items")
fun <T> RecyclerView.setItems(items: List<T>?) {
(adapter as? ListAdapter<T, *>)?.submitList(items) {
layoutManager?.onSaveInstanceState().let {
layoutManager?.onRestoreInstanceState(it)
}
}
}
mMessageAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
#Override
public void onChanged() {
mLayoutManager.smoothScrollToPosition(mMessageRecycler, null, mMessageAdapter.getItemCount());
}
});
The solution here is to keep on scrolling recyclerview when new message comes.
The onChanged() method detects the action performed on recyclerview.
That's working for me in Kotlin.
Create the Adapter and hand over your data in the constructor
class LEDRecyclerAdapter (var currentPole: Pole): RecyclerView.Adapter<RecyclerView.ViewHolder>() { ... }
change this property and call notifyDataSetChanged()
adapter.currentPole = pole
adapter.notifyDataSetChanged()
The scroll offset doesn't change.
If you have one or more EditTexts inside of a recyclerview items, disable the autofocus of these, putting this configuration in the parent view of recyclerview:
android:focusable="true"
android:focusableInTouchMode="true"
I had this issue when I started another activity launched from a recyclerview item, when I came back and set an update of one field in one item with notifyItemChanged(position) the scroll of RV moves, and my conclusion was that, the autofocus of EditText Items, the code above solved my issue.
best.
Just return if the oldPosition and position is same;
private int oldPosition = -1;
public void notifyItemSetChanged(int position, boolean hasDownloaded) {
if (oldPosition == position) {
return;
}
oldPosition = position;
RLog.d(TAG, " notifyItemSetChanged :: " + position);
DBMessageModel m = mMessages.get(position);
m.setVideoHasDownloaded(hasDownloaded);
notifyItemChanged(position, m);
}
I had this problem with a list of items which each had a time in minutes until they were 'due' and needed updating. I'd update the data and then after, call
orderAdapter.notifyDataSetChanged();
and it'd scroll to the top every time. I replaced that with
for(int i = 0; i < orderArrayList.size(); i++){
orderAdapter.notifyItemChanged(i);
}
and it was fine. None of the other methods in this thread worked for me. In using this method though, it made each individual item flash when it was updated so I also had to put this in the parent fragment's onCreateView
RecyclerView.ItemAnimator animator = orderRecycler.getItemAnimator();
if (animator instanceof SimpleItemAnimator) {
((SimpleItemAnimator) animator).setSupportsChangeAnimations(false);
}
I want to implement search functionality for my RecyclerView. On text changed i want to change the data that are displayed with this widget. Maybe this question has been asked before or is simple, but I don't know how the change the data that is to be shown...
My RecyclerView is defined as follows:
// 1. get a reference to recyclerView
mRecyclerView = (RecyclerView)findViewById(R.id.recyclerView);
// 2. set layoutManger
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
// 3. create an adapter
mAdapter = new ItemsAdapter(itemsData);
// 4. set adapter
mRecyclerView.setAdapter(mAdapter);
And the data that I am showing is something like:
ItemData itemsData[] = { new ItemData("Mary Richards"),
new ItemData("Tom Brown"),
new ItemData("Lucy London")
};
So when when I want to give the adapter another set of data, another array (with one item for example), what should I do?
If you have stable ids in your adapter, you can get pretty good results (animations) if you create a new array containing the filtered items and call
recyclerView.swapAdapter(newAdapter, false);
Using swapAdapter hints RecyclerView that it can re-use view holders. (vs in setAdapter, it has to recycle all views and re-create because it does not know that the new adapter has the same ViewHolder set with the old adapter).
A better approach would be finding which items are removed and calling notifyItemRemoved(index). Don't forget to actually remove the item. This will let RecyclerView run predictive animations. Assuming you have an Adapter that internally uses an ArrayList, implementation would look like this:
// adapter code
final List<ItemData> mItems = new ArrayList(); //contains your items
public void filterOut(String filter) {
final int size = mItems.size();
for(int i = size - 1; i>= 0; i--) {
if (mItems.get(i).test(filter) == false) {
mItems.remove(i);
notifyItemRemoved(i);
}
}
}
It would perform even better if you can batch notifyItemRemoved calls and use notifyItemRangeRemoved instead. It would look sth like: (not tested)
public void filterOut(String filter) {
final int size = mItems.size();
int batchCount = 0; // continuous # of items that are being removed
for(int i = size - 1; i>= 0; i--) {
if (mItems.get(i).test(filter) == false) {
mItems.remove(i);
batchCount ++;
} else if (batchCount != 0) { // dispatch batch
notifyItemRangeRemoved(i + 1, batchCount);
batchCount = 0;
}
}
// notify for remaining
if (batchCount != 0) { // dispatch remaining
notifyItemRangeRemoved(0, batchCount);
}
}
You need to extend this code to add items that were previously filtered out but now should be visible (e.g. user deletes the filter query) but I think this one should give the basic idea.
Keep in mind that, each notify item call affects the ones after it (which is why I'm traversing the list from end to avoid it). Traversing from end also helps ArrayList's remove method performance (less items to shift).
For example, if you were traversing the list from the beginning and remove the first two items.
You should either call
notifyItemRangeRemoved(0, 2); // 2 items starting from index 0
or if you dispatch them one by one
notifyItemRemoved(0);
notifyItemRemoved(0);//because after the previous one is removed, this item is at position 0
This is my answer - thanks to Ivan Skoric from his site: http://blog.lovelyhq.com/creating-lists-with-recyclerview-in-android/
I created an extra method inside my adapter class:
public void updateList(List<Data> data) {
mData = data;
notifyDataSetChanged();
}
Then each time your data changes, you just call this method passing in your new data and your view should change to reflect it.
Just re-initialize your adapter:
mAdapter = new ItemsAdapter(newItemsData);
or if you only need to remove add a few specific items rather than a whole list:
mAdapter.notifyItemInserted(position);
or
mAdapter.notifyItemRemoved(position);
If you want to change the complete Adapter in the recycler view. you can just simply set by recycler.setAdapter(myAdapter);
It will automatically remove the old adapter from recycler view and replace it with your new adapter.
As ygit answered, swapAdapter is interesting when you have to change the whole content.
But, in my FlexibleAdapter, you can update the items with updateDataSet. You can even configure the adapter to call notifyDataSetChanged or having synchronization animations (enabled by default). That, because notifyDataSetChanged kills all the animations, but it's good to have for big lists.
Please have a look at the description, demoApp and Wiki pages: https://github.com/davideas/FlexibleAdapter