Android Button implements Checkable doesn't change drawable

I have to create a set of View representing week's days and that are checkable, to select and deselect the availability in that day. Days buttons layout

I create a custom view that extends Button and implements Checkable. I assigned a selector drawable to it in order to change color when checked.

The problem is that it doesn't change drawable when clicked. Do I need to specify in the listener that it has to change drawable? It's not yet a Checkable property?

I can't use any other Checkable View like Toggle, ChechedTextView, cause I need this particular style for the view.

CheckableButton

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.Button;
import android.widget.Checkable;

public class CheckableButton extends Button implements Checkable {


private static final int[] CHECKED_STATE_SET =   {android.R.attr.state_checked};

private boolean mChecked = false;

private OnCheckedChangeListener mOnCheckedChangeListener;

public CheckableButton(Context context, AttributeSet attrs) {
    super(context, attrs);
}

public boolean isChecked() {
    return mChecked;
}

public void setChecked(boolean b) {
    if (b != mChecked) {
        mChecked = b;
        refreshDrawableState();

        if (mOnCheckedChangeListener != null) {
            mOnCheckedChangeListener.onCheckedChanged(this, mChecked);
        }
    }
}

public void toggle() {
    setChecked(!mChecked);
}

@Override
public int[] onCreateDrawableState(int extraSpace) {
    final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);
    if (isChecked()) {
        mergeDrawableStates(drawableState, CHECKED_STATE_SET);
    }
    return drawableState;
}


public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {
    mOnCheckedChangeListener = listener;
}

public static interface OnCheckedChangeListener {

    void onCheckedChanged(View checkableView, boolean isChecked);
}
}

layout (part of)

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


            <eu.ecomind.pitagora.utils.CheckableButton
                android:id="@+id/mon"
                android:layout_width="0dp"
                android:layout_height="40dp"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:background="@drawable/day_selection"
                android:gravity="center"
                android:text="L"
                android:textColor="@color/text_background_dark_customer" />

            <eu.ecomind.pitagora.utils.CheckableButton
                android:id="@+id/tue"
                android:layout_width="0dp"
                android:layout_height="40dp"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:background="@drawable/day_selection"
                android:gravity="center"
                android:text="M"
                android:textColor="@color/text_background_dark_customer" />

            <eu.ecomind.pitagora.utils.CheckableButton
                android:id="@+id/wed"
                android:layout_width="0dp"
                android:layout_height="40dp"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:background="@drawable/day_selection"
                android:gravity="center"
                android:text="M"
                android:textColor="@color/text_background_dark_customer" />

            <eu.ecomind.pitagora.utils.CheckableButton
                android:id="@+id/thu"
                android:layout_width="0dp"
                android:layout_height="40dp"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:background="@drawable/day_selection"
                android:gravity="center"
                android:text="G"
                android:textColor="@color/text_background_dark_customer" />

            <eu.ecomind.pitagora.utils.CheckableButton
                android:id="@+id/fri"
                android:layout_width="0dp"
                android:layout_height="40dp"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:background="@drawable/day_selection"
                android:gravity="center"
                android:text="V"
                android:textColor="@color/text_background_dark_customer" />

            <eu.ecomind.pitagora.utils.CheckableButton
                android:id="@+id/sat"
                android:layout_width="0dp"
                android:layout_height="40dp"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:background="@drawable/day_selection"
                android:gravity="center"
                android:text="S"
                android:textColor="@color/text_background_dark_customer" />

            <eu.ecomind.pitagora.utils.CheckableButton
                android:id="@+id/sun"
                android:layout_width="0dp"
                android:layout_height="40dp"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:background="@drawable/day_selection"
                android:gravity="center"
                android:text="D"
                android:textColor="@color/text_background_dark_customer" />



        </LinearLayout>

selector

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://ift.tt/nIICcg">
<item android:drawable="@drawable/day_selected"
    android:state_checked="true"/>
<item android:drawable="@drawable/day_not_selected"/>
</selector>