【ANDROID STUDIO】 recycler view action mode

package com.example.recyclerviewactionmode;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.view.ActionMode;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements SelectMode {
    MyAdapter myAdapter;
    ActionMode mActionMode;


    private ActionMode.Callback mActionModeCallback = new ActionMode.Callback() {
        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            mode.getMenuInflater().inflate(R.menu.context_menu, menu);
            return true;
        }

        @Override
        public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
            return false;
        }

        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            switch (item.getItemId()) {
                case R.id.delete_all:
                    myAdapter.deleteAllSelected();
                    mode.finish();
                    return true;
                default:
                    return false;
            }
        }

        @Override
        public void onDestroyActionMode(ActionMode mode) {
            mActionMode = null;
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        List<String> list = new ArrayList<>();
        list.add("China");
        list.add("France");
        list.add("Germany");
        list.add("India");
        list.add("Russia");
        list.add("United Kingdom");
        list.add("United States");

        RecyclerView recyclerView = findViewById(R.id.recyclerView);

        recyclerView.setHasFixedSize(true);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(linearLayoutManager);

        myAdapter = new MyAdapter(list, this);
        recyclerView.setAdapter(myAdapter);
    }

    @Override
    public void onSelect() {
        if (mActionMode != null) return;
        mActionMode = startSupportActionMode(mActionModeCallback);
    }

}

package com.example.recyclerviewactionmode;

import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>
implements SelectMode {  //Added implements

    private SelectMode mListener;
    private List<String> nameList;
    //Added following list
    private SparseArray<Boolean> selectedList = new SparseArray<>();

    public MyAdapter(List<String> list, SelectMode listener) { //Added listener to parameters
        nameList = list;
        mListener = listener;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        View view = inflater.inflate(R.layout.item, parent, false);
        MyViewHolder myViewHolder = new MyViewHolder(view);
        return myViewHolder;
    }

    @Override
    public void onBindViewHolder(@NonNull final MyViewHolder holder, final int position) {
        final String name = nameList.get(position);
        holder.textView.setText(name);
        holder.itemView.setSelected(selectedList.get(position, false)); //New (for There's more)

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                holder.itemView.setSelected(!holder.itemView.isSelected());
                if (holder.itemView.isSelected()) {
                    selectedList.put(position, true);
                } else {
                    selectedList.remove(position);
                }
                onSelect();
            }
        });
    }

    @Override
    public int getItemCount() {
        if (nameList == null) {
            return 0;
        } else {
            return nameList.size();
        }
    }

    private void remove(int position) {
        nameList.remove(position);
        notifyItemRemoved(position);
    }

    //New method
    public void deleteAllSelected() {
        if (selectedList.size() == 0) {
            return;
        }
        for (int index = nameList.size() - 1; index >= 0; index--) {
            if (selectedList.get(index, false)) {
                remove(index);
            }
        }
        selectedList.clear();
    }

    @Override
    public void onSelect() {
        if (mListener != null) {
            mListener.onSelect();
        }
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView textView;

        public MyViewHolder(View itemVieww) {
            super(itemVieww);
            textView = itemView.findViewById(R.id.textView);
        }
    }

}
package com.example.recyclerviewactionmode;

public interface SelectMode {
    void onSelect();
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>


</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="TextView" />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:id="@+id/delete_all"
        android:title="@string/delete_all" />
</menu>