Should use app:showAsAction with the appcompat library with xmlns:app="http://schemas.android.com/apk/res-auto" less... (Ctrl+F1)
When using the appcompat library, menu resources should refer to the showAsAction in the app: namespace, not the android: namespace.
Similarly, when not using the appcompat library, you should be using the android:showAsAction attribute.
你的sdk版本太旧了，你下载个新版本吧