Add selected position in RecyclerView to a set and highlight those position

Question

I have a recyclerView and have implemented onLongClick listener on the items. The Adapter is in the same class as the Activity.

I created a set: public Set<Integer> multiplePositions as instance variable of the Activity class and am initialising it in onCreate() method as multiplePositions = new TreeSet<>().Coming to my Adapter class in the onBindViewHolder method I created a click listener as follows:

holder.textCardView.setOnLongClickListener(new View.OnLongClickListener() {

                @Override
                public boolean onLongClick(View v) {

                    Adapter.this.onLongClick(holder, position);

                    return true;
                }
            });
            holder.textCardView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {


                }
            });

As you can see I am calling the method onLongClick. My onLongClick method looks like this:

public void onLongClick(ViewHolder holder, int position) {

        multiplePositions.add(position);

        for(Integer i : multiplePositions) {
            Log.e("set", ""+i);


        }
        holder.textCardView.setBackgroundResource(R.color.long_press);

}

Here, whenever an item clicked I am adding the position in the Set but I don't know how do I iterate through this set and set the background color of all the item at the positions in the set.

I am aware that this can be achieved by creating a boolean variable isSelected in the model class but if I go with this method then other functionalities of my code won't work.

My main concern is if I scroll the recyclerView up or down then color of the selected positions should not disappear. The unselection part will be done in setOnClickListener().

see this http://droidmentor.com/multi-select-like-whatsapp-android/ — Vij, Sep 21 '17 at 12:29
do not add any listeners inside `onBindViewHolder` - why dont you simply follow the code i gave you? you want the solution without `boolean isSelected`? then use `SparseBooleanArray` - set it in click listener an read it inside `onBindViewHolder` — pskink, Sep 21 '17 at 13:16
so this [Adapter](https://pastebin.com/raw/ttpL00cM) uses `SparseBooleanArray`, does it differ much from "booolean flag" in data model? no, not really — pskink, Sep 21 '17 at 13:38
I want it working and right now I am modifying the code with the one which you gave me — localhost, Sep 22 '17 at 06:07

Sharath kumar · Answer 1 · 2017-09-21T13:03:51.270

0

Use SparseBoolean array to store the positions of the items clicked in the reyclerview.Check the answer in this link

https://stackoverflow.com/questions/46336645/hilighted-selected-items-colour-changes-when-not-in-view-in-recyclerview/46336844#46336844

Check here the purpose of using SparseBoolean array

https://stackoverflow.com/questions/18822708/what-is-the-clear-purpose-of-sparsebooleanarray-i-referred-official-android

EDIT: Use SparseBooleanArray to keep track of selected items in recycler view adapter

Initialize the SparseBooleanArray as private memeber variable

private SparseBooleanArray mClickedItems=new SparseBooleanArray();

Inside your click function while clicking textCardView make the item position as true.

            holder.textCardView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mClickedItems.put(position,true);
               notifyDataSetChanged();

            }
            });

Then in the onBindViewHolder check if the position is already selected or not like this

if(mClickedItems.get(position)==true){
        //Show selected color
    holder.textCardView.setBackgroundResource(ContextCompat.getColor(holder.textCardView.getContext(),R.drawable.selected));                                              

    }else {
        //show unselected color

   holder.textCardView.setBackgroundResource(ContextCompat.getColor(holder.textCardView.getContext(),R.drawable.unselected));
    }

edited Sep 21 '17 at 13:03

answered Sep 21 '17 at 12:28

Sharath kumar

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I tried this but I am not able to get it work. Would you guide me through the process. – localhost Sep 21 '17 at 12:36
Did you check that answer?I have explained there how to add and handle items there – Sharath kumar Sep 21 '17 at 12:37
I created private SparseBooleanArray mClickedItems=new SparseBooleanArray(); as the instance variable in the Activity Class – localhost Sep 21 '17 at 12:41
I added answer..check that – Sharath kumar Sep 21 '17 at 12:42
what your are doing in onLongClickListener? – Sharath kumar Sep 21 '17 at 12:44
where you want to store clicked item posistion add the code there – Sharath kumar Sep 21 '17 at 12:47
in the if else part you need to add code to change color also..remember that no...add setbackground inside if and else – Sharath kumar Sep 21 '17 at 12:52
yes, I put the code to change the background color but still it is not working. – localhost Sep 21 '17 at 12:56
you cant pass R.color.long_press to background resource..check that once..try adding drawable and check – Sharath kumar Sep 21 '17 at 13:00
sure, let me give a try – localhost Sep 21 '17 at 13:05
are you getting error?post something or I cant guess error – Sharath kumar Sep 21 '17 at 13:19
I am not getting any error. There is no messages to find the exact reason why it is not working – localhost Sep 21 '17 at 13:25
debug and check – Sharath kumar Sep 21 '17 at 13:28

Add selected position in RecyclerView to a set and highlight those position

1 Answers1