How to add admob ads in fragments in android studio?

I would love to add admob ads to fragments in my app. I have already added the ads in the XML files. I am having trouble in the java part, however. Could you please share the java code with rootview? I have checked other articles but I am confused.

HomeFragment.java

private AdView mAdView;
@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootview = inflater.inflate(R.layout.fragment_home, container, false);
    ButterKnife.bind(this, rootview);
    mFragmentPositionMap = CommonCodeUtils.getInstance().fillNavigationItemsMap(true);

    mAdView = findViewById(R.id.adView);
    AdRequest adRequest = new AdRequest.Builder().build();
    mAdView.loadAd(adRequest);    

    imagesToPdf.setOnClickListener(this);
    qrbarcodeToPdf.setOnClickListener(this);
    textToPdf.setOnClickListener(this);
    viewFiles.setOnClickListener(this);
    viewHistory.setOnClickListener(this);
    splitPdf.setOnClickListener(this);
    mergePdf.setOnClickListener(this);
    compressPdf.setOnClickListener(this);
    removePages.setOnClickListener(this);
    rearrangePages.setOnClickListener(this);
    extractImages.setOnClickListener(this);
    mPdfToImages.setOnClickListener(this);
    addPassword.setOnClickListener(this);
    removePassword.setOnClickListener(this);
    rotatePdf.setOnClickListener(this);
    addWatermark.setOnClickListener(this);
    addImages.setOnClickListener(this);
    removeDuplicatePages.setOnClickListener(this);
    invertPdf.setOnClickListener(this);
    zipToPdf.setOnClickListener(this);
    excelToPdf.setOnClickListener(this);
    extractText.setOnClickListener(this);
    addText.setOnClickListener(this);

    mAdapter =  new RecentListAdapter(this);
    recentList.setAdapter(mAdapter);
    return rootview;
    }

Added This To fragment_home.xml

<com.google.android.gms.ads.AdView
    xmlns:ads="http://schemas.android.com/apk/res-auto"
    android:id="@+id/adView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_alignParentBottom="true"
    ads:adSize="BANNER"
    ads:adUnitId="ca-app-pub-3940256099942544/6300978111">
</com.google.android.gms.ads.AdView>

However, it return an error with the findViewById part. And I would also like to know what should be added to the Manifest file.

You have to run this on your Activity:

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

    MobileAds.initialize(this, new OnInitializationCompleteListener() {
        @Override
        public void onInitializationComplete(InitializationStatus initializationStatus) {}
    });
}

and this on your Fragment:

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    AdView adView = findViewById(R.id.adView);
    AdRequest adRequest = new AdRequest.Builder().build();
    adView.loadAd(adRequest);
}