半透明のActionBarを画面下に表示する ref: http://qiita.com/kuchinashi_r/items/254d8c7a9d5c58c362b8

main_activity.xml

    <RelativeLayout
        android:id="@+id/rootLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/bg_1920x1080" />

MainActivity.java

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_activity.xml);
    getWindow().getDecorView().setBackgroundResource(R.drawable.bg_1920x1080);

style.xml

    <style name="Theme.MainActivity.ActionBar" parent="@android:style/Widget.Holo.ActionBar">
        <item name="android:background">#88ffffff</item>
    </style>

Utils.java

public class Utils {
    private static final String TAG = Utils.class.getSimpleName();

    /**
     * ActionBarを画面下部に表示する
     * 
     * @param activity
     */
    public final static void actionBarUpsideDown(Activity activity) {
        View root = activity.getWindow().getDecorView();
        View firstChild = ((ViewGroup) root).getChildAt(0);
        if (firstChild instanceof ViewGroup) {
            ViewGroup viewGroup = (ViewGroup) firstChild;
            List<View> views = findViewsWithClassName(root,
                    "com.android.internal.widget.ActionBarContainer");
            if (!views.isEmpty()) {
                for (View vv : views) {
                    viewGroup.removeView(vv);
                }
                for (View vv : views) {
                    viewGroup.addView(vv);
                }
            }
        } else {
            Log.e(TAG, "first child is not ViewGroup.");
        }
    }

    private static List<View> findViewsWithClassName(View v, String className) {
        List<View> views = new ArrayList<View>();
        findViewsWithClass(v, className, views);
        return views;
    }

    @SuppressWarnings("unchecked")
    private static <T extends View> void findViewsWithClass(View v, String clazz, List<T> views) {
        if (v.getClass().getName().equals(clazz)) {
            views.add((T) v);
        }
        if (v instanceof ViewGroup) {
            ViewGroup g = (ViewGroup) v;
            for (int i = 0; i < g.getChildCount(); i++) {
                findViewsWithClass(g.getChildAt(i), clazz, views);
            }
        }
    }

    private Utils() {
        // ignore
    }
}