Develop Reference

RecyclerView notifyItemRangeInserted not maintaining scroll position

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..

Get all items from adapter (recyclerview) in Fragment

Hello I'm having an issue getting all of the items from my adapter in my fragment. To be more specific I am using a ScaleInAnimatorAdapter along with my Customer Adapter and when I attempt to get my checkbox items from the below posted code, within my Fragment, I only seem to get the visible items on screen.
private View.OnClickListener onAllClick = new View.OnClickListener() {
#Override public void onClick(View v) {
int count = listAdapter.getItemCount();
for (int i = 0; i < count; i++) {
View mChild = listTopics.getChildAt(i);
if( mChild != null ) {
Log.d(TAG,"getItemCount(): " + i );
CheckBox cBox = (CheckBox)mChild.findViewById(R.id.topic_chk);
cBox.setChecked(((CheckBox) v).isChecked());
Log.d(TAG,"isChecked" + cBox.getTag());
cBox.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(((CheckBox) v).isChecked()) {
checkboxAll.setChecked(false);
}
}
});
}
}
}
};
Essentially I am attempting to create a check all feature from the fragment, so that when this is clicked all of the checkbox items from the adapter are checked. I got that to work with the code I presented however the main issue is that I only get the items visible on the screen, so when I scroll to my other items they are not checked. Thus I am wondering if there is a better way or another way for me to get all of the items

Adapters are meant to bind underlying data stores to views; they generally shouldn't be used to store data themselves (except for having a copy of the data for view binding purposes) nor should they perform actions on data.
Instead, you should be modifying the underlying data, then updating the adapter through whatever mechanism you are already using. (Loaders, custom setters with notifyDataItemChanged, etc.).

Basically you can't. It'll be reusing the UI views.
You need to set a flag in all your data list objects, call notifyDataSetChanged() and onBindViewHolder check that flag and use it to check uncheck
if(listAdapter.getItem(position).getIsChecked())
viewHolder.checkBox.setChecked(true);
else
viewHolder.checkBox.setChecked(false);

Ok. Thank you all for those who have replied you helped me grasp something really basic and important that had alluded me.
I got it to work, so for anyone who might read this post, here is my solution:
Create necessary methods and field to update your data in a model (ie, private is_checked, set_checked(), is_checked(), etc)
In your adapter onBindViewHolder, you will set your holder checkbox to be associated to the data so something like:
holder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
obj.setSelected(buttonView.isChecked());
}
});
holder.checkBox.setChecked(obj.isSelected());
Then in your fragment or activity I just have a click listener on my main checkbox, and then when checked I loop through my data list, and using the model method I update my data and just simply use listAdapter.notifyDataSetChanged()

You are doing it wrongly.
You should update the adapter instead of updating the check box view.
What you can do , you can create a field in adapter data holder .
And whenever you change the selection,just update the field or multiple field and finally refresh the view.

Click on last item in AdapterView in Espresso

I'm working on a note taking app. I add a note, and it get's added to the bottom of the list. As the last assertion in the espresso test, I want to make sure that the ListView displays a listItem that has just been added. This would mean grabbing the last item in the listView. I guess you might be able to do it in other ways? (e.g. get the size of adapted data, and go to THAT position? maybe?), but the last position of the list seems easy, but I haven't been able to do it. Any ideas?
I've tried this solution, but Espresso seems to hang. http://www.gilvegliach.it/?id=1

1. Find the number of elements in listView's adapter and save it in some variable. We assume the adapter has been fully loaded till now.:
final int[] numberOfAdapterItems = new int[1];
onView(withId(R.id.some_list_view)).check(matches(new TypeSafeMatcher<View>() {
#Override
public boolean matchesSafely(View view) {
ListView listView = (ListView) view;
//here we assume the adapter has been fully loaded already
numberOfAdapterItems[0] = listView.getAdapter().getCount();
return true;
}
#Override
public void describeTo(Description description) {
}
}));
2. Then, knowing the total number of elements in listView's adapter you can scroll to the last element:
onData(anything()).inAdapterView(withId(R.id.some_list_view)).getPosition(numberOfAdapterItems[0] - 1).perform(scrollTo())

How to refresh two listview at one moment in Android?

I have two listview, like listview_1 and listview_2. I wanna refresh the listview_2 while listview_1 is refreshed.
My code like this:
public void updateTwoListView() {
listview_1.getAdapter().notifyDataSetChanged();
listview_2.getAdapter().notifyDataSetChanged();
}
But it don't work, listview_1 can refresh but the listview_2 can't.
And at that moment what I found is that listview_1 was on focus.
And then I tried to set focus to other views before ran the method, both of them didn't refresh. It likes to refresh a listview only if the listview has focus.
What's more I found that when I called the method to refresh, listview_2 didn't, and then I set focus to listview_2, refreshed itself!
So, What all I want to ask is:
How to refresh two listview at one moment in Android?
What's more code:
//init two listview there
public void init() {
listview_1 = (ListView)findViewById(R.id.listView1);
listview_2 = (ListView)findViewById(R.id.listView2);
adapter1 = new MyListViewAdapter(mContext);
adapter2 = new MyListViewAdapter(mContext); //I have tried use different adapter, that also didn't work.
listview_1.setAdapter(adapter1);
listView_2.setAdapter(adapter2);
}
the real code of upside snippet is:
public void updateTwoListView(int currentPosition) {
adapter1.updateCurPos(currentPosition);
adapter2.updateCurPos(currentPosition);
}
and in MyListViewAdapter.java:
public void updateCurPos(int currentPosition) {
mCurrentPos = currentPosition;
notifyDataSetChanged();
}
And I will call method like listViewManager.updateTwoListView(1) outside to refresh.
Any reply is appreciated.

You have called listview_1 twice. Just change one of them to listview_2 as below:
public void updateTwoListView() {
listview_1.getAdapter().notifyDataSetChanged();
listview_2.getAdapter().notifyDataSetChanged();
}

It seems the problem of your code is that you call getAdapter().
Sets the data behind this ListView. The adapter passed to this method may be wrapped by a WrapperListAdapter, depending on the ListView features currently in use. For instance, adding headers and/or footers will cause the adapter to be wrapped.
Source: http://developer.android.com/reference/android/widget/ListView.html#setAdapter(android.widget.ListAdapter)
The solution is save your Adapter as member variable in your activity and call the notifyDataSetChanged()from there.
See more on this question's answer: https://stackoverflow.com/a/31893525/2742759

Android RecyclerView infinity scrolling: how to add more items to dataset

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);
}
}
}