Set a custom Font to ActionBar Tabs.

FontSetter.java

ViewParent root = findViewById(android.R.id.content).getParent();
setCustomFontToActionBarTab(root);

TabsFont.java

    // Set a custom font on all of our ActionBar Tabs
    private boolean setCustomFontToActionBarTab(Object root) {

        // Found the container, that holds the Tabs. This is the ScrollContainerView to be specific,
        // but checking against that class is not possible, since it's part of the hidden API.
        // We will check, if root is an derivative of HorizontalScrollView instead,
        // since ScrollContainerView extends HorizontalScrollView.
        if (root instanceof HorizontalScrollView) {
            // The Tabs are all wraped in a LinearLayout
            root = ((ViewGroup) root).getChildAt(0);
            if (root instanceof LinearLayout) {
                // Found the Tabs. Now we can set a custom Font to all of them.
                for (int i = 0; i < ((ViewGroup) root).getChildCount(); i++) {
                    LinearLayout child = ((LinearLayout)((ViewGroup) root).getChildAt(i));
                    TextView actionBarTitle = (TextView) child.getChildAt(0);
                    Typeface tf = Typeface.createFromAsset(mContext.getAssets(), "font/font.ttf");
                    actionBarTitle.setTypeface(tf);
                }
                return true;
            }
            
        } 
        // Search ActionBar and the Tabs. Exclude the content of the app from this search.
        else if (root instanceof ViewGroup) {
            ViewGroup group = (ViewGroup) root;
            if (group.getId() != android.R.id.content) {
                // Found a container that isn't the container holding our screen layout.
                // The Tabs have to be in here.
                for (int i = 0; i < group.getChildCount(); i++) {
                    if (setCustomFontToActionBarTab(group.getChildAt(i))) {
                        // Found and done searching the View tree
                        return true;
                    }
                }
            }
        }
        // Found nothing
        return false;
    }