Typeface droidSerifMonoTF = Typeface.createFromAsset(getAssets(), "fonts/DroidSerif.ttf");

for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            TextView t = new TextView(this);
            t.setText(mSectionsPagerAdapter.getPageTitle(i) );
            t.setTypeface(droidSansMonoTF);

            actionBar.addTab(actionBar.newTab()
                    .setCustomView(t)
                    .setTabListener(this));

        }

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom){
    super.onLayout(changed, left, top, right, bottom);

    final ViewGroup tabStrip = (ViewGroup)getChildAt(0);
    final int tabCount = tabStrip.getChildCount();
    ViewGroup tabView;
    int tabChildCount;
    View tabViewChild;

    for(int i=0; i<tabCount; i++){
        tabView = (ViewGroup)tabStrip.getChildAt(i);
        tabChildCount = tabView.getChildCount();
        for(int j=0; j<tabChildCount; j++){
            tabViewChild = tabView.getChildAt(j);
            if(tabViewChild instanceof AppCompatTextView){
                if(fontFace == null){
                    fontFace = Typeface.createFromAsset(context.getAssets(), context.getString(R.string.IranSans));
                }
                ((TextView) tabViewChild).setTypeface(fontFace, Typeface.BOLD);
            }
        }
    }
}

if(fontFace == null){
    fontFace = Typeface.createFromAsset(context.getAssets(), context.getString(R.string.IranSans));
}

<style name="tabLayoutTitles">
    <item name="android:textColor">@color/white</item>
    <item name="android:textSize">@dimen/appFirstFontSize</item>
    <item name="android:fontFamily">@font/vazir_bold</item>
</style>

<style name="defaultTabLayout">
    <item name="android:layout_width">match_parent</item>
    <item name="android:layout_height">@dimen/defaultTabLayoutHeight</item>
    <item name="android:gravity">right</item>
    <item name="tabTextAppearance">@style/tabLayoutTitles</item>
    <item name="tabSelectedTextColor">@color/white</item>
    <item name="tabIndicatorColor">@color/white</item>
    <item name="tabIndicatorHeight">@dimen/accomTabIndicatorHeight</item>
    <item name="tabMode">fixed</item>
    <item name="tabGravity">fill</item>
    <item name="tabBackground">@drawable/rectangle_white_ripple</item>
    <item name="android:background">@color/colorPrimary</item>
</style>