Using FrameLayout Change forground frames an image

package com.example.frameapp;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {
    Button btn ;
    ImageView imageView;
    int index = -1;
int Frames[] ={R.drawable.a,R.drawable.b,R.drawable.c}; //images array 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        imageView = findViewById(R.id.imageView);
        btn = findViewById(R.id.button);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(index<Frames.length-1)
                    index++;
                else
                    index = 0;
                imageView.setImageResource(Frames[index]);
            }
        });
    }
}




//Layout Xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center_horizontal"
    android:orientation="vertical"
    tools:context=".MainActivity">



    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ImageView

            android:id="@+id/imageView2"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:padding="5dp"
            android:scaleX="-1"
            android:scaleType="fitXY"
            android:src="@drawable/zuckerberg" /> //image 

        <ImageView
            android:id="@+id/imageView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_margin="10dp"
            android:scaleType="fitXY"
            android:src="@drawable/b" /> //image
        <Button
            android:id="@+id/button"
            android:layout_gravity="center|bottom"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Change" />

    </FrameLayout>


</LinearLayout>