How to get "?android:attr/actionBarSize" with Compatibility Library

I'm trying to use Fragments and ActionBar in a Android 2.开发者_Go百科2 project. There is some error when using "?android:attr/actionBarSize", how to get and set that value correctly?

Example:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/frags">

    <fragment class="com.example.android.hcgallery.TitlesFragment"
            android:id="@+id/frag_title"
            android:visibility="gone"
            android:layout_marginTop="?android:attr/actionBarSize"
            android:layout_width="@dimen/titles_size"
            android:layout_height="match_parent" />

    <fragment class="com.example.android.hcgallery.ContentFragment"
            android:id="@+id/frag_content"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

</LinearLayout>

Error: No resource found that matches the given name (at 'layout_marginTop' with value '?android:attr/actionBarSize').

You should just use:

android:layout_marginTop="?attr/actionBarSize"

See http://developer.android.com/training/basics/actionbar/overlaying.html

"...The one with the android: prefix is for versions of Android that include the style in the platform and the one without the prefix is for older versions that read the style from the Support Library..."

For me replacing

android:layout_marginTop="?android:attr/actionBarSize" 

with

android:layout_marginTop="?attr/actionBarSize" 

helped to launch app on Android 2.2 and Android 4.3 without any issues.

I think the problem is that actionbar comes with android 3.0 and you are using 2.2. But there is a way to skip this by a extension called "actionbarsherlock".