I just integrated ActionBar into my Android app (actually, I ultimately went with ActionBarSherlock for its backward compatibility).
To display the ActionBar on an activity, you must use a particular set of themes: Theme.Holo.* for ActionBar or Theme.Sherlock.* for ActionBarSherlock
Whenever I modify the AndroidManifest.xml so that the style of an existing activity uses one of the aforementioned ActionBar themes, I find that the background image of each Button on the activity becomes distorted. Specifically, the image gets stretched vertically across more pixels than the image actually contains. I would expect that behavior only if I was using layout_height="fill_parent", but I am not. Furthermore, this doesn't seem to happen with other themes (other than the ActionBar-related themes).
I tried posting screenshots, but I don't have a high enough reputation yet. I apologize.
Here is one of my Button declarations that is being affected adversely by the Theme:
<Button
android:textStyle="bold"
android:typeface="sans"
android:layout_height="wrap_content"
android:id="@+id/btnAddtoBag" android:layout_width="wrap_content"
android:background="@drawable/add_to_bag_selector">
</Button>
Since that references a selector, I will include the XML of the selector also, where the actual png files are referenced:
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true"
android:drawable="@drawable/selected_add_to_bag" /> <!-- pressed -->
<item android:state_focused="true"
android:drawable="@drawable/selected_add_to_bag" /> <!-- focussed -->
<item android:drawable="@drawable/default_add_to_bag" /> <!-- default -->
</selector>
Finally, here is the style that I'm applying to my theme when this happens:
<style name="Theme.CustomActionBar" parent="Theme.Sherlock.Light.DarkActionBar.ForceOverflow">
<item name="actionBarStyle">@style/ActionBar</item>
</style>
<style name="ActionBar" parent="Widget.Sherlock.Light.ActionBar.Solid.Inverse">
<item name="android:displayOptions">showHome|useLogo</item>
<item name="displayOptions">showHome|useLogo</item>
</style>