例如：
<activity android:name="com.google.android.gms.ads.AdActivity" android:theme="@android:style/Theme.NoTitleBar.Fullscreen" tools:replace="android:theme" />
添加：
xmlns:tools="http://schemas.android.com/tools"
at the top of the manifest (or activity).
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.mypackage" xmlns:tools="http://schemas.android.com/tools">