How to check if a checkbox inside a spinner is checked? [Android Studio]

So, I do have a MainActivity were inside there is a spinner

Java code:

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

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

        final boolean[] selected_action = {false, false, false};

        final String[] select_action = {"Select the option(s)",
                "WhatsApp backup databases", "Images Miniature", "Caches"};
        Spinner spinner = (Spinner) findViewById(R.id.spinner);

        ArrayList<StateVO> listVOs = new ArrayList<>();

        for (String aSelect_action : select_action) {
            StateVO stateVO = new StateVO();
            stateVO.setTitle(aSelect_action);
            stateVO.setSelected(stateVO.isSelected());
            listVOs.add(stateVO);
        }

        MyAdapter myAdapter = new MyAdapter(MainActivity.this, 0, listVOs);

        spinner.setAdapter(myAdapter);

        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {

                for (int i = 0; i < selected_action.length; i++) {

                    if (selected_action[i]) {

                        Toast.makeText(MainActivity.this, "True", Toast.LENGTH_SHORT).show();

                    }

                }

            }
        });

    }

}

And here it is the XML code:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.lorenzomoscati.remover.MainActivity">

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="164dp" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="61dp"
        android:text="@string/start" />

</RelativeLayout>

Cool, then I've made a StateVO.java for the spinner as well as a custom adapter called MyAdapter.java.

StateVO.java:

public class StateVO {
    private String title;
    private boolean selected;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    boolean isSelected() {
        return selected;
    }

    void setSelected(boolean selected) {
        this.selected = selected;
    }

}

MyAdapter.java:

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.TextView;
import android.widget.CompoundButton;

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

public class MyAdapter extends ArrayAdapter<StateVO> {
    private Context mContext;
    private ArrayList<StateVO> listState;
    private MyAdapter myAdapter;
    private boolean isFromView = false;

    public MyAdapter(Context context, int resource, List<StateVO> objects) {
        super(context, resource, objects);
        this.mContext = context;
        this.listState = (ArrayList<StateVO>) objects;
        this.myAdapter = this;
    }

    @Override
    public View getDropDownView(int position, View convertView,
                                ViewGroup parent) {
        return getCustomView(position, convertView, parent);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        return getCustomView(position, convertView, parent);
    }

    public View getCustomView(final int position, View convertView,
                              ViewGroup parent) {

        final ViewHolder holder;
        if (convertView == null) {
            LayoutInflater layoutInflater = LayoutInflater.from(mContext);
            convertView = layoutInflater.inflate(R.layout.spinner_item, null);
            holder = new ViewHolder();
            holder.mTextView = (TextView) convertView
                    .findViewById(R.id.text);
            holder.mCheckBox = (CheckBox) convertView
                    .findViewById(R.id.checkbox);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.mTextView.setText(listState.get(position).getTitle());

        isFromView = true;
        holder.mCheckBox.setChecked(listState.get(position).isSelected());
        isFromView = false;

        if ((position == 0)) {
            holder.mCheckBox.setVisibility(View.INVISIBLE);
        } else {
            holder.mCheckBox.setVisibility(View.VISIBLE);
        }
        holder.mCheckBox.setTag(position);
        holder.mCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                int getPosition = (Integer) buttonView.getTag();

            }
        });
        return convertView;


    }

    private class ViewHolder {
        private TextView mTextView;
        private CheckBox mCheckBox;
    }
}

So the problem is the following: How do I get checked if the checkboxes inside the spinner are checked or nor? In which file do I have to put the checking code? What should be like the checking code?

I've tried a lot (OnClick for example), but I didn't get so far. Probably because I implemented the code in a wrong way. I'd be glad if anyone can help.