액션바 android:showAsAction="ifRoom" 이부분 질문이요! [closed]

Question

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" tools:context=".Main">

    <item android:id="@+id/menu1"
           android:icon="@mipmap/ic_launcher"
           android:title="강아지를 찾습니다"
           android:showAsAction="ifRoom" />

소스는 이렇구요, 왜 android:showAsAction="ifRoom" 부분에서 계속 빨간줄이 쳐질까요ㅠㅠ?