C# Xamarin.表单AdMob“缺少AdActivity”

我在Xamarin.Forms项目中实现AdMob时遇到问题

因此，当我运行android应用程序时，输出中会显示：

01-22 16:53:17.351 W/Ads (3529): Missing AdActivity with android:configChanges in AndroidManifest.xml. 
You must have the following declaration within the <application> element:
<activity android:name="com.google.android.gms.ads.AdActivity"
android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" />

当我打开包含广告的页面时，会显示：

这里怎么了？

标签应该在标签里面

<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:installLocation="auto">
    <uses-sdk android:minSdkVersion="15" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <activity android:name="com.google.android.gms.ads.AdActivity" android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" />

<application>
    <activity android:name="com.google.android.gms.ads.AdActivity" android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" />
</application>