To have a centered title in ABS (if you want to have this in the default ActionBar, just remove the "support" in the method names), you could just do this:

In your Activity, in your onCreate() method:

getSupportActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM); 
getSupportActionBar().setCustomView(R.layout.abs_layout);

abs_layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
        android:layout_gravity="center"
    android:orientation="vertical">

    <android.support.v7.widget.AppCompatTextView
        android:id="@+id/tvTitle"
        style="@style/TextAppearance.AppCompat.Widget.ActionBar.Title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textColor="#FFFFFF" />

</LinearLayout>

Now you should have an Actionbar with just a title. If you want to set a custom background, set it in the Layout above (but then don't forget to set android:layout_height="match_parent").

or with:

getSupportActionBar().setBackgroundDrawable(getResources().getDrawable(R.drawable.yourimage));