How can I put Native Ads in Exit Popup without Admob?

Question

I want to use Applovin MAX SDK.
I created a Native ad unit but I don't know how to insert.
There are some guides about inserting native ads in Exit Popup with Admob Native ads.
Please help me.

MainActiviy.java

@Override
public void onBackPressed() {

    ExitDialog exitDialog = new ExitDialog(MainActivity.this, this.adobj);
    exitDialog.show();

    Window window = exitDialog.getWindow();
    window.setLayout(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);
}

ExitDialog.java

public class ExitDialog extends Dialog {

    UnifiedNativeAd ad;
    Activity activity;

    public ExitDialog(Activity activity, UnifiedNativeAd ad){
        super(activity);
        this.activity = activity;
        this.ad = ad;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.end);

        TextView quit = findViewById(R.id.dialog_button_exit_yes);
        TextView cancel = findViewById(R.id.dialog_button_exit_no);

        quit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                activity.finish();
            }
        });

        cancel.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view) {
                dismiss();
            }
        });

        TemplateView ad = findViewById(R.id.ad_template);

        if (this.ad == null){
            ad.setVisibility(View.GONE);
        }
        else {
            ad.setVisibility(View.VISIBLE);
            ad.setNativeAd(this.ad);
        }

    }

}

What should be modified?