I am making a simple application and when i monetize it and but it doesnt start

In Logcat It shows the following error

2020-05-11 21:37:48.149 12929-12929/com.example.rao E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.rao, PID: 12929 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.rao/com.example.rao.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.ads.AdView.loadAd(com.google.android.gms.ads.AdRequest)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3153) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3303) at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:114) at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:74) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1989) at android.os.Handler.dispatchMessage(Handler.java:106) at android.os.Looper.loop(Looper.java:226) at android.app.ActivityThread.main(ActivityThread.java:7214) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:500) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:888) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.ads.AdView.loadAd(com.google.android.gms.ads.AdRequest)' on a null object reference at com.example.rao.MainActivity.onCreate(MainActivity.java:37) at android.app.Activity.performCreate(Activity.java:7337) at android.app.Activity.performCreate(Activity.java:7328) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3133) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3303)  at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)  at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:114)  at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:74)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1989)  at android.os.Handler.dispatchMessage(Handler.java:106)  at android.os.Looper.loop(Looper.java:226)  at android.app.ActivityThread.main(ActivityThread.java:7214)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:500)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:888)  2020-05-11 21:37:48.157 12929-13013/com.example.rao I/Adreno: PFP: 0x016ee183, ME: 0x00000000 2020-05-11 21:37:48.177 12929-12929/com.example.rao I/Process: Sending signal. PID: 12929 SIG: 9

My mainActivity.java

package com.example.rao;

import androidx.appcompat.app.AppCompatActivity;

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

import com.google.android.gms.ads.AdListener;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.MobileAds;
import com.google.android.gms.ads.initialization.InitializationStatus;
import com.google.android.gms.ads.initialization.OnInitializationCompleteListener;

public class MainActivity extends AppCompatActivity {

    private Button BtnMove;
    private AdView mAdView;
    private Bundle savedInstanceState;
    private Bundle savedInstanceStateTwo;

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

        MobileAds.initialize(this, new OnInitializationCompleteListener() {
            @Override
            public void onInitializationComplete(InitializationStatus initializationStatus) {
            }
        });
        mAdView = findViewById(R.id.adView);
        AdRequest adRequestBanner = new AdRequest.Builder().build();
        AdView adView = (AdView) this.findViewById(R.id.adViewone);
        mAdView.loadAd(adRequestBanner);

        mAdView.setAdListener(new AdListener() {
            @Override
            public void onAdLoaded() {
                // Code to be executed when an ad finishes loading.
            }

            @Override
            public void onAdFailedToLoad(int errorCode) {
                // Code to be executed when an ad request fails.
            }

            @Override
            public void onAdOpened() {
                // Code to be executed when an ad opens an overlay that
                // covers the screen.
            }

            @Override
            public void onAdClicked() {
                // Code to be executed when the user clicks on an ad.
            }

            @Override
            public void onAdLeftApplication() {
                // Code to be executed when the user has left the app.
            }

            @Override
            public void onAdClosed() {
                // Code to be executed when the user is about to return
                // to the app after tapping on an ad.
            }
        });



        BtnMove = findViewById(R.id.BtnActivityOne);

        BtnMove.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                moveToScreenActivity2();
            }

        });
    }


    private void moveToScreenActivity2() {

        Intent intent = new Intent(MainActivity.this, ScreenActivity2.class);
        startActivity(intent);
    }
}

Check your R.layout.activity_main if your AdView's id is R.id.adViewone, perhaps you should modify your MainActivity from:

mAdView = findViewById(R.id.adView);
AdRequest adRequestBanner = new AdRequest.Builder().build();
AdView adView = (AdView) this.findViewById(R.id.adViewone);

to:

AdRequest adRequestBanner = new AdRequest.Builder().build();
mAdView = (AdView) findViewById(R.id.adViewone);