Dialogue Box Android Studio

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:background="#7fdbd1"
    >


    <TextView
        android:id="@+id/tv1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="This is The Example of using Dialog"
        android:textSize="40sp"
        android:gravity="center_horizontal"
        />

    <TextView
        android:id="@+id/tv2"
        android:layout_below="@+id/tv1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:textStyle="bold"
        android:textColor="#a8a232"
        android:text="Tap Button below To Display the dialog"
        android:textSize="20dp" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tv2"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_marginTop="81dp"
        android:layout_marginEnd="152dp"
        android:layout_marginRight="152dp"
        android:foregroundGravity="center_horizontal"
        android:src="@drawable/ic_launcher_foreground" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentBottom="true"
        android:layout_marginStart="163dp"
        android:layout_marginLeft="163dp"
        android:layout_marginEnd="160dp"
        android:layout_marginRight="160dp"
        android:layout_marginBottom="179dp"
        android:background="#000000"
        android:text="Open!"
        android:textColor="#b634c9"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</RelativeLayout>

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    private Button button;
    //we declare are button


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

  //we initialize are button and set a on click listener
        button=(Button)findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                opration();
            }
        });
    }
// in main activity we create are method opration() for that we add a java class

    public void opration() {
        dialogX dialogX = new dialogX();
        dialogX.show(getSupportFragmentManager(),"dialogX");


    }
}

package com.example.myapplication;

import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;

import androidx.appcompat.app.AppCompatDialogFragment;

public class dialogX extends AppCompatDialogFragment {

    // we override our on click method with on create dialog
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {

        //create function here
        AlertDialog.Builder builder= new AlertDialog.Builder(getActivity());
        builder.setTitle("Operation done")
                .setMessage("Positive")
                .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                });
        //we return our function
     return builder.create();
    }
}