CardView selected background color in RecyclerView

Question

i am trying to write a RecyclerView with CardViews and using CAB trying to delete multiple Cards on selection .How do i give background color to the selected cards. i am trying to use statelistdrawable as the following :

<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_activated="true" android:drawable="@color/primary_dark" />

    <item android:drawable="@android:color/transparent" />

</selector>

and apply it to the CardView layout as :

<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/card_view"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
android:background="@drawable/statelist_item_background"
        card_view:cardCornerRadius="10dp"
    card_view:cardElevation="10dp"
android:layout_marginTop="5dp"
android:layout_marginBottom="5dp"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"


    >


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"

        >

        <ImageView
            android:id="@+id/imageView"
            android:tag="image_tag"
            android:layout_width="72dp"
            android:layout_height="100dp"
            android:layout_margin="5dp"
            android:layout_weight="1"
            android:src="@drawable/one"/>

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="12dp"
            android:layout_weight="2"
            android:orientation="vertical"
            >

            <TextView
                android:id="@+id/textViewName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_horizontal"
                android:layout_marginTop="10dp"
                android:text="Large Text"
                android:textAppearance="?android:attr/textAppearanceLarge"/>

            <TextView
                android:id="@+id/textViewEmail"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_horizontal"
                android:layout_marginTop="10dp"

                android:text="Medium Text"
                android:textAppearance="?android:attr/textAppearanceMedium"/>

        </LinearLayout>
    </LinearLayout>

</android.support.v7.widget.CardView>

below is the code for my adapter

public class modeladapter extends RecyclerView.Adapter<modeladapter.myholder> {

    ArrayList<MyModel> arraylist;
SparseBooleanArray selecteditems;
    public modeladapter(ArrayList<MyModel> ar) {
        arraylist=ar;
        selecteditems=new SparseBooleanArray();
    }

    public void removeData(int position) {
        arraylist.remove(position);
        notifyItemRemoved(position);
    }

    public MyModel getItem(int position) {
        return arraylist.get(position);
    }

    public void addData(MyModel newModelData, int position) {
        arraylist.add(position, newModelData);
        notifyItemInserted(position);
    }

    public void toggleSelection(int pos) {
        if (selecteditems.get(pos, false)) {
            selecteditems.delete(pos);
        }
        else {
            selecteditems.put(pos, true);
        }
        notifyItemChanged(pos);
    }

    public void clearSelections() {
        selecteditems.clear();
        notifyDataSetChanged();
    }

    public int getSelectedItemCount() {
        return selecteditems.size();
    }

    public List<Integer> getSelectedItems() {
        List<Integer> items = new ArrayList<Integer>(selecteditems.size());
        for (int i = 0; i < selecteditems.size(); i++) {
            items.add(selecteditems.keyAt(i));
        }
        return items;
    }





    @Override
    public modeladapter.myholder onCreateViewHolder(ViewGroup viewGroup, int i) {
        LayoutInflater lf=LayoutInflater.from(viewGroup.getContext());

            View v = lf.inflate(R.layout.card_lay, viewGroup, false);

//            v.setOnClickListener(Activity_Main.listener);
            myholder m=new myholder(v);
            return m;



    }


    @Override
    public void onBindViewHolder(modeladapter.myholder m, int i) {

                m.cimage.setImageResource(arraylist.get(i).url);
                m.email.setText(arraylist.get(i).email);
                m.name.setText(arraylist.get(i).name);
m.itemView.setActivated(selecteditems.get(i,false));

         }

    @Override
    public int getItemCount()  {return (arraylist.size());}

    public static class myholder extends RecyclerView.ViewHolder
    {
        ImageView cimage;
        TextView name,email;

        public myholder(View itemView) {
            super(itemView);
            cimage= (ImageView) itemView.findViewById(R.id.imageView);
            name= (TextView) itemView.findViewById(R.id.textViewName);
            email= (TextView) itemView.findViewById(R.id.textViewEmail);
            if(itemView.isActivated())
                itemView.setBackgroundColor(itemView.getContext().getResources().getColor(R.color.primary_dark));
            else
                itemView.setBackgroundColor(Color.parseColor("#ffffff"));
        }
    }

kindly update how i can change the background color of selected items. thanks

Answer 1

You do not necessarily need to have a StateListDrawable You need to have a method in your adapter that checks for selections:

sparseArray.valueAt(i).isSelected()

Then in your RecylcerView.Adapter, change:

if (itemView.isActivated())
    itemView.setBackgroundColor(itemView.getContext().getResources().getColor(R.color.primary_dark));
else
    itemView.setBackgroundColor(Color.parseColor("#ffffff"));

To(You need to change the cardView, not the itemView):

 viewHolder.cardView.setCardBackgroundColor(sparseArray.valueAt(i).isSelected() ? Color.LTGRAY : Color.WHITE);