Develop Reference

In Recycler View with multiple view types items duplicating on scrollup

I have a recyclerview with multiple view types and pagination enabled. Scrolling up after two pages the items are not holding the view and are duplicating. I have implemented getItemId return unique id and getViewtype return unique value. Also have the the adapter's setHasStableIds to true. Looking forward for any help.
Thank you.
getItemId
if (postList.get(position).getId()== null){
return position;
} else{
return postList.get(position).getId();
}
getItemViewType
if (postList.get(position).getPostType().equals("contest")){
return TYPE_CONTEST;
} else if(postList.get(position).getPostType().equals("suggestion")){
return TYPE_SUGGESTION;
} else{
return TYPE_POST_POLL;
}
} else{
return TYPE_HEADER;
}

Try something like this:
#Override
public int getItemViewType(int position) {
if (isValidPosition(position)) {
Dataset d = mDataset[position];
if ("contest".equals(d.getViewType())) {
return VIEW_TYPE_CONTEST;
} else if ("suggestion".equals(d.getViewType())) {
return VIEW_TYPE_SUGGESTION;
}
// all other cases here
}
// default type
return VIEW_TYPE_CONTEST;
}
and then :
#Override
public void onBindViewHolder(ViewHolder holder, int position) {
Dataset d = mDataset[position];
if (holder instanceof ContestVH) {
ContestDataset contest = (ContestDataset) d;
ContestVH vh = (ContestVH) holder;
// bind your contest views here
} else if (holder instanceof SuggestionVH) {
SuggestionDataset suggestion = (SuggestionDataset) d;
SuggestionVH vh = (SuggestionVH) holder;
// bind your suggestion views here
}
// all other cases here
}
this way your String view type is your only source of truth.

For pagination in recyclerview you should use onScrollListener this
recyclerList.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
boolean isLast = isLastItemDisplaying(recyclerView); //get last displayed item
if (loading && isLast) { //this check if your data is loading and if its last list item list will not load again
loading = false;
//get your data according to page count it will refresh your recycler list
}
}
});
because in pagination you can get data from Api on page scroll in recycler view. So data will come in chunks according to page count. For this behaviour you can use on scroll listener in recycler list and refresh data on scroll of list until last item of list arrived.
i hope it will help you :)

How to highlight the first row of RecyclerView by default and then remove highlight as and when other rows are selected?

I am trying to load a list in RecyclerView and show the first row of the list as selected. I have achieved it using the following code:
#Override
public void onBindViewHolder(NavigationDrawerAdapter.ViewHolder holder, final int position) {
if (!mNavClassrooms.get(position).equals("")) {
holder.mTextViewClassroom.setText(mNavClassrooms.get(position)); // Setting the Text with the array of our Titles
holder.mRelLayClassroom.setSelected(mSelectedItems.get(position, false));
/*
The following code was written to make the first item in the Classroom list as selected.
It leads to the item always being selected and hence has been commented out.
*/
if(position == 0 && intOldSelectedItem == -1){
holder.mRelLayClassroom.setSelected(mSelectedItems.get(position, true));
intOldSelectedItem = 0;
mSelectedView = holder.mRelLayClassroom.getChildAt(position);
mSelectedItems.put(position, true);
}
else{
holder.mRelLayClassroom.setSelected(mSelectedItems.get(position, false));
}
} else {
holder.mTextViewClassroom.setText("No classes found");
holder.mTextViewClassroom.setPadding(40, 0, 0, 0);
}
holder.mRelLayClassroom.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
mSharedPreferences = mContext.getSharedPreferences(Constants.AAPREFERENCES, Context.MODE_PRIVATE);
String strClassroomValue = mNavClassrooms.get(position);
int strClassroomName = mNavClassroomNames.get(position);
SharedPreferences.Editor editor = mSharedPreferences.edit();
editor.putString(Constants.CLASSROOM_VALUE, strClassroomValue);
editor.putInt(Constants.CLASSROOM_NAME, strClassroomName);
editor.commit();
/*
We are storing the position of the selected row in the SparseBooleanArray.
We delete it in case another row has been selected.
*/
if (mSelectedItems.get(position, false)) {
/*
Do nothing
*/
} else {
mSelectedItems.put(position, true);
/*
Making sure that the delete code is called only if some view is selected
*/
if (mSelectedView != null) {
mSelectedView.setSelected(false);
mSelectedItems.delete(intOldSelectedItem);
view.setSelected(false);
}
mSelectedView = view;
intOldSelectedItem = position;
view.setSelected(true);
}
}
However, now the first row stays selected always. I am unable to deselect it. I cannot seem to get this working.
I referred to the following answer to achieve most of this functionlaity.
https://stackoverflow.com/a/29984220/2186220
Any help will be appreciated.

I'm not answering your question by posting a fixed version of your onBindViewHolder method since it's kinda hard to understand and we don't know how the rest of your adapter looks like. So following a RecyclerView Adapter which does what you want: Selecting the first row by default and deselecting it once a other row is selected.
public class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
// ... other fields
// default selection position is the first one
private int selectedPosition = 0;
// ... constructor etc.
#Override
public void onBindViewHolder(final ViewHolder holder, int position) {
if(position == selectedPosition){
holder.itemView.setSelected(true);
} else {
holder.itemView.setSelected(false);
}
// Actual selection / deselection logic
holder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
int currentPosition = holder.getLayoutPosition();
if(selectedPosition != currentPosition){
// Temporarily save the last selected position
int lastSelectedPosition = selectedPosition;
// Save the new selected position
selectedPosition = currentPosition;
// update the previous selected row
notifyItemChanged(lastSelectedPosition);
// select the clicked row
holder.itemView.setSelected(true);
}
}
});
// other adapter code
}
// other adapter stuff like onCreateViewHolder, getItemCount, ViewHolder etc.
}
Note: I guess there's no need to use a SparseBooleanArray so simply remove it and replace it with the int field used in the example above.

Initialize your
int intOldSelectedItem=0 and keep one boolean isVisible= false;
And do it as below:
if (holder.getPosition() == intOldSelectedItem) {
if (isVisible) {
//background for selected item
} else {
//background for unselected item
}
} else {
//background for unselected item
}
holder.mRelLayClassroom.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (intOldSelectedItem== holder.getPosition()) {
isVisible = !isVisible;
} else {
if (intOldSelectedItem!= 0) {
isVisible = false;
notifyItemChanged(intOldSelectedItem);
}
isVisible = true;
}
intOldSelectedItem= holder.getPosition();
notifyItemChanged(intOldSelectedItem);
}
});
I hope it might help you.

Add background selector to your ViewHolder layout.
Create your selector handler something like this:
public class SingleSelector {
private View oldVIew;
public void setSelection(View newView) {
if (oldVIew == null) {
newView.setSelected(true);
oldVIew = newView;
} else {
oldVIew.setSelected(false);
newView.setSelected(true);
oldVIew = newView;
}
}
}
Set default selection when you need it:
#Override
public void onBindViewHolder(SimpleViewHolder holder, int position) {
if (position == 0) {
singleSelector.setSelection(holder.itemView);
}
}
In your ViewHolder add listener to itemView and pass it to the handler:
itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
singleSelector.setSelection(itemView);
}
});

Force RecyclerView to call onCreateViewHolder

I have a RecyclerView that can show items as list, small grids or large grid and this can be change at runtime. Depending on what style user chooses i inflate different layout in onCreateViewHolder.
I also use layoutManger.setSpanSizeLookUp() to switch between styles. My code looks like this
layoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
#Override
public int getSpanSize(int position) {
if(showType == ProductAdapter.SHOW_TYPE_SMALL_GRID)
return 1;
else
return columnCount; //show one item per row
}
});
#Override
public void onClick(View v) {
if(showType == ProductAdapter.SHOW_TYPE_SMALL_GRID)
showType = ProductAdapter.SHOW_TYPE_LARGE_GRID;
else
showType = ProductAdapter.SHOW_TYPE_SMALL_GRID;
int firstVisibleItem = layoutManager.findFirstVisibleItemPosition();
adapter = new ProductAdapter(getActivity(), productList, showType);
recyclerView.setAdapter(adapter);
layoutManager.scrollToPosition(firstVisibleItem);
}
The problem is to force onCreateViewHolder to be called I'm creating a new object every time user changes the style. Is there any other way?! to force onBindViewHolder() to be recalled. I simply use adapter.notifyDataSetChanged() How can i get something similar for onCreateViewHolder?
Any solution that doesn't uses multiple adapters is good enough!

What you need to do is:
Modify your Adapter:
Specify two types of Views that your Adapter can inflate:
private static final int LARGE_GRID_ITEM = -1;
private static final int SMALL_GRID_ITEM = -2;
Create a field that can store current type mCurrentType
Use your Adapter's getItemViewType. For example like this:
#Override
public int getItemViewType (int position) {
return mCurrentType;
}
In your createViewHolder use the viewType to decide what type of ViewHolder you need to create.
public final RecyclerView.ViewHolder createViewHolder (ViewGroup parent, int viewType){
if (viewType == LARGE_GRID_ITEM) {
//return large grid view holder
} else {
//return small grid view holder
}
}
Additionally you can create methods:
public void toggleItemViewType () {
if (mCurrentType == LARGE_GRID_ITEM){
mCurrentType = SMALL_GRID_ITEM;
} else {
mCurrentType = LARGE_GRID_ITEM;
}
}
public boolean displaysLargeGrid(){
return mCurrentType == LARGE_GRID_ITEM;
}
Modify the code you posted:
layoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
#Override
public int getSpanSize(int position) {
if (adapter.displaysLargeGrid()) {
return 1;
} else {
return columnCount; //show one item per row
}
}
});
#Override
public void onClick(View v) {
adapter.toggleItemViewType();
adapter.notifyDataSetChanged();
}

Its not the optimal choice but it's better to create a new Adapter, which will call onCreateViewHolder(). This way you can avoid your troubles, by the cost of very tiny performance issues.

using notifyItemRemoved or notifyDataSetChanged with RecyclerView in Android

I am creating a list of cards to display using the RecyclerView, where each card has a button to remove that card from the list.
When i use notifyItemRemoved() to remove the card in the RecyclerView, it removes the item and animates fine but the data in the list is not updated correctly.
If instead of that, i switch to the notifyDataSetChanged() then the items in list are removed and updated correctly, but then the cards dont animate.
Does someone has any experience in using the notifyItemRemoved() and know why it behaves differently than notifyDataSetChanged?
Here is some peiece of code that i am using:
private List<DetectedIssue> issues = new ArrayList<DetectedIssue>();
#Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
// - get element from your dataset at this position
// - replace the contents of the view with that element
if(position >0){
RiskViewHolder riskHolder = (RiskViewHolder)holder;
final int index = position - 1;
final DetectedIssue anIssue = issues.get(index);
riskHolder.button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
int index = issues.indexOf(anIssue);
issues.remove(anIssue);
notifyItemRemoved(index);
//notifyDataSetChanged();
} catch (SQLException e) {
e.printStackTrace();
}
}
});
}
}
#Override
public int getItemCount() {
return (issues.size()+1);
}

Use notifyItemRangeChanged(position, getItemCount()); after notifyItemRemoved(position);
You don't need to use index, just use position. See code below.
private List<DetectedIssue> issues = new ArrayList<DetectedIssue>();
#Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
// - get element from your dataset at this position
// - replace the contents of the view with that element
if(position >0){
RiskViewHolder riskHolder = (RiskViewHolder)holder;
riskHolder.button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
issues.remove(position);
notifyItemRemoved(position);
//this line below gives you the animation and also updates the
//list items after the deleted item
notifyItemRangeChanged(position, getItemCount());
} catch (SQLException e) {
e.printStackTrace();
}
}
});
}
}
#Override
public int getItemCount() {
return issues.size();
}

Tried
public void removeItem(int position) {
this.taskLists.remove(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position, getItemCount() - position);
}
and working like a charm.

my mistake ,
notifyItemChanged(position) is helpless,the item of position can be removed ,and the item of position+1 is fine,but the items start from position+2,you will get an Exception, please use notifyItemRangeChanged(position,getItemCount());
after notifyItemRemoved(position);
like this:
public void removeData(int position) {
yourdatalist.remove(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position,getItemCount());
}

Use this it is working perfectly.
issues.remove(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position, issues.size());

As #pskink suggested it was supposed to be (index+1) in my case with notifyItemRemoved(index+1), probably because i am reserving the top index i.e. position=0 for a header.

**my solution looks like this**
this way is unnecessary to use the heavy method:
//notifyItemRangeChanged(xx,xx)
/**
*
* recyclerView的item中的某一个view,获取其最外层的viewParent，也就是item对应的layout在adapter中的position
*
* #param recyclerView
* #param view：can be the deep one inside the item,or the item itself .
* #return
*/
public static int getParentAdapterPosition(RecyclerView recyclerView, View view, int parentId) {
if (view.getId() == parentId)
return recyclerView.getChildAdapterPosition(view);
View viewGroup = (View) view.getParent();
if (viewGroup != null && viewGroup.getId() == parentId) {
return recyclerView.getChildAdapterPosition(viewGroup);
}
//recursion
return getParentAdapterPosition(recyclerView, viewGroup, parentId);
}
//wherever you set the clickListener .
holder.setOnClickListener(R.id.rLayout_device_item, deviceItemClickListener);
holder.setOnLongClickListener(R.id.rLayout_device_item, deviceItemLongClickListener);
#Override
public boolean onLongClick(View v) {
final int position = ViewUtils.getParentAdapterPosition(rVDevicesList, v, R.id.rLayout_device_item);
return true;
}

In my case I use Content Provider and a Custom RecyclerView Adapter with Cursor. This line of code is where you notify:
getContext().getContentResolver().notifyChange(uri, null);
Assuming In your recyclerView adapter (Delete Button):
Uri currentUri = ContentUris.withAppendedId(DatabaseContract.ToDoEntry.CONTENT_URI_TODO, id);
int rowsDeleted = mContext.getContentResolver().delete(currentUri, null, null);
if (rowsDeleted == 0) {
Log.d(TAG, "onClick: Delete failed");
} else {
Log.d(TAG, "onClick: Delete Successful");
}
And in your Database Provider:
case TODO_ID:
selection = DatabaseContract.ToDoEntry._ID + "=?";
selectionArgs = new String[] {String.valueOf(ContentUris.parseId(uri))};
rowsDeleted = database.delete(DatabaseContract.ToDoEntry.TODO_TABLE_NAME, selection, selectionArgs);
if (rowsDeleted != 0){
getContext().getContentResolver().notifyChange(uri, null);
}
return rowsDeleted;

You can use getAdapterPosition() from the RecyclerView.ViewHolder
getLayoutPosition() provides the exact position of item in the layout and code is
holder.removeButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Position for remove
int modPosition= holder.getAdapterPosition();
//remove item from dataset
numbers.remove(modPosition);
//remove item from recycler view
if(numbers.isEmpty())
notifyDataSetChanged ()
else
notifyItemRemoved(modPosition);
}
});

Android: Select ListView Item in onResume

I have an Activity that hosts multiple fragments using the actionbar's tab functionality. One of those fragments contains a ListView. Upon this tab being selected, I'd like to select a certain item.
To do this programmatically, I use the following code (where calls is the ListView)
private void selectItem(int position)
{
long itemId = calls.GetItemIdAtPosition(position);
calls.PerformItemClick(calls, position, itemId);
}
If this ListView has been rendered, and I'm calling this, no problem. However, if I call it from onResume, then the code executes but nothing is selected in the end. I figure this is because at the point where I'm calling selectItem, not all items of the ListView have been rendered yet. If however I start off a background thread, sleep for a couple hundred milliseconds, then run the same code (in the ui thread of course), everything is fine, but this is an ugly hack.
Now you might be wondering, "why isn't he using calls.setSelection"? The thing is, I'm using a custom layout that performs expansion - so I need to actually click on the item I want selected (which in turn triggers the layout expansion for the item selected). However, I can call the code that is performed on PerformItemClick directly, the results will be the same (the layout expansion isn't performed).
Isn't there any way for me to catch the "Listview has finished rendering all viewable items" point in time, and then execute my selectItem call at that point? In ASP.NET, I have an event on every UI item telling me when it is done rendering, so I do item selection at that point but I haven't found anything.
Regards
Stephan
Here's the Adapter I'm using
public class ActiveCallsAdapter: ObservableAdapter<Call>
{
public ActiveCallsAdapter(Activity activity, ObservableCollection<Call> calls)
: base(activity, calls)
{
}
public override View GetView(int position, View convertView, ViewGroup parent)
{
var item = items[position];
var view = (convertView ?? context.LayoutInflater.Inflate(Resource.Layout.Call, parent, false)) as LinearLayout;
//View view = convertView;
//if (view == null) // no view to re-use, create new
// view = context.LayoutInflater.Inflate(Resource.Layout.Call, null);
SetTextView(view, Resource.Id.CallerName, item.CallerName);
SetTextView(view, Resource.Id.CallerNumber, item.CallerNumber);
SetTextView(view, Resource.Id.CallStatus, item.State.ToString());
SetTextView(view, Resource.Id.CallDuration, item.Duration);
return view;
}
public void Update(LinearLayout view, Call item)
{
SetTextView(view, Resource.Id.CallerName, item.CallerName);
SetTextView(view, Resource.Id.CallerNumber, item.CallerNumber);
string identifier = "callState_" + item.State.ToString();
int resourceId = Application.Context.Resources.GetIdentifier(identifier, "string", Application.Context.PackageName);
string callStateString = item.State.ToString();
if (resourceId != 0)
{
try
{
callStateString = Application.Context.Resources.GetString(resourceId);
}
catch (Exception e)
{
AndroidLogModel.Model.AddLogMessage("ActiveCallsAdapter", "Unable to find call state string with resource id " + resourceId + " state string: " + identifier, 3);
}
}
SetTextView(view, Resource.Id.CallStatus, callStateString);
//SetTextView(view, Resource.Id.CallDuration, item.Duration);
}
public void UpdateDuration(LinearLayout view, Call item)
{
SetTextView(view, Resource.Id.CallDuration, item.Duration);
}
}
And the base class of that adapter
public class ObservableAdapter<T>: BaseAdapter<T>
{
protected readonly Activity context;
protected readonly ObservableCollection<T> items;
public ObservableAdapter(Activity context, ObservableCollection<T> collection)
{
this.context = context;
this.items = collection;
//this.collection.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(collection_CollectionChanged);
this.items.CollectionChanged += (sender, e) => NotifyDataSetChanged();
}
void collection_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
NotifyDataSetChanged();
}
public override T this[int position]
{
get { return items[position]; }
}
public override int Count
{
get { return items.Count; }
}
public override long GetItemId(int position)
{
return position;
}
public override View GetView(int position, View convertView, ViewGroup parent)
{
var item = items[position];
var view = (convertView ?? context.LayoutInflater.Inflate(Resource.Layout.Call, parent, false)) as LinearLayout;
// configure view here
return view;
}
protected void SetTextView(LinearLayout view, int id, string text)
{
var textView = view.FindViewById<TextView>(id);
if (textView != null)
textView.SetText(text, TextView.BufferType.Normal);
}
}

My Mono skills are limited so I don't know if I fully understood your adapter, anyway I've adapted some old code and made an adapter that expands a single item when click, also it will move the ListView in onResume to a desired position:
private static class CustomAdapter extends BaseAdapter {
// the data
private ArrayList<String> mData;
// an int pointing to a position that has an expanded layout,
// for simplicity I assume that you expand only one item(otherwise use
// an array or list)
private int mExpandedPosition = -1; // -1 meaning no expanded item
private LayoutInflater mInflater;
public CustomAdapter(Context context, ArrayList<String> items) {
mInflater = LayoutInflater.from(context);
mData = items;
}
public void setExpandedPosition(int position) {
// if the position equals mExpandedPosition then we have a click on
// the same row so simply toggle the row to be gone again
if (position == mExpandedPosition) {
mExpandedPosition = -1;
} else {
// else change position of the row that was expanded
mExpandedPosition = position;
}
// notify the adapter
notifyDataSetChanged();
}
#Override
public int getCount() {
return mData.size();
}
#Override
public String getItem(int position) {
return mData.get(position);
}
#Override
public long getItemId(int position) {
return position;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = mInflater.inflate(R.layout.ad_expandedelement,
parent, false);
}
((TextView) convertView.findViewById(R.id.textView1))
.setText(getItem(position));
// see if there is an expanded position and if we are at that
// position
if (mExpandedPosition != -1 && mExpandedPosition == position) {
// if yes simply expand the layout
convertView.findViewById(R.id.button1).setVisibility(
View.VISIBLE);
} else {
// this is required, we must revert any possible changes
// otherwise the recycling mechanism will hurt us
convertView.findViewById(R.id.button1).setVisibility(View.GONE);
}
return convertView;
}
}
The onListItemClick will simply be:
#Override
protected void onListItemClick(ListView l, View v, int position, long id) {
// set the expanded(or collapsed if it's a click on the same row that
// was previously expanded) row in the adapter
((CustomAdapter) getListView().getAdapter())
.setExpandedPosition(position);
}
and in onResume will have:
#Override
protected void onResume() {
super.onResume();
// set the position to the desired element
((CustomAdapter) getListView().getAdapter()).setExpandedPosition(15);
// set the selection to that element so we can actually see it
// this isn't required but has the advantage that it will move the
// ListView to the desired
// position if not visible
getListView().setSelection(15);
}
The R.layout.ad_expandedelement is a simple vertical LinearLayout with a TextView and an initially hidden(visibility set to gone) Button. For this Button I change the visibility to simulate expanding/collapsing a row in the ListView. You should be able to understand my code, if you want I can post on github the full sample.

While I'm not sure of the exact equivalent in C#/Mono, the Android framework provides a callback on Activity called onWindowFocusChanged() that indicates the period when the Window associated with a given Activity is visible to the user. You may have better luck waiting to call your selection method until that time, as the ListView should be measured and laid out by that point. In Java, it would be something like this:
#Override
public void onWindowFocusChanged (boolean hasFocus) {
if (hasFocus) {
selectItem(position);
}
}
You may need to have a bit more logic in there, this callback is directly associated with window focus and isn't a true lifecycle method. I can get called multiple times if you are displaying Dialogs or doing other similar operations.