我正在尝试将Admob本机广告添加到我的应用程序中。但是，当应用程序启动时，没有广告显示。显示错误：

 Caused by: android.view.InflateException: Binary XML file line #13: Binary XML file line #13: Error inflating class com.google.android.ads.nativetemplates.TemplateView
 Caused by: android.view.InflateException: Binary XML file line #13: Error inflating class com.google.android.ads.nativetemplates.TemplateView
 Caused by: java.lang.reflect.invocationTargetException

我不明白自己做错了什么。

这是我的xml代码

<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.LinearLayoutCompat xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:ads="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:orientation="vertical"
    android:layout_height="match_parent"
    tools:context=".Mainactivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <com.google.android.gms.ads.NativeExpressAdView
        android:id="@+id/adView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        ads:adUnitId="ca-app-pub-3940256099942544/2247696110"
        ads:adSize="300x220">
    </com.google.android.gms.ads.NativeExpressAdView>

</androidx.appcompat.widget.LinearLayoutCompat>

这是活动代码

public class Mainactivity extends AppCompatactivity {

    private NativeExpressAdView nativeExpressAdView;

    @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) {
            }
        });

        nativeExpressAdView=findViewById(R.id.adView);
        nativeExpressAdView.loadAd(new AdRequest.Builder().build());
    }
}