Why was ActionBarActivity deprecated

Here is the answer from the post in Android developers blog:

"ActionBarActivity has been deprecated in favor of the new AppCompatActivity."

You can read more about it there.

ActionBar is deprecated ever since Toolbar was introduced. Toolbar can be seen as a 'superset' of any action bar. So the 'old' ActionBar is now an example of a Toolbar. If you want similar functionality, but without deprecation warnings do the following:

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
if (toolbar != null) {
    toolbar.setTitle(R.string.app_name);
    setSupportActionBar(toolbar);
}

You need to define the Toolbar in your layout xml:

<android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/toolbar"
    android:minHeight="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    android:popupTheme="@style/ThemeOverlay.AppCompat.Light">
</android.support.v7.widget.Toolbar>

With this new functionality you can create your own custom ActionBar and let Android do the heavy lifting. Just create your own custom view that extends from Toolbar.

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Also, you should use AppCompatActivity instead of ActionBarActivity, it was introduced in the latest version of the appcompat library. So dont forget to update gradle

compile 'com.android.support:appcompat-v7:22.1.1'