android - Change the font and color of Action Bar title using AppCompat v7 -

i have developed android app few months ago targets api 19 , compiled api 19. 1 of things did changed font of action bar title , color dynamically based on scrolling , other factors. have used method below:

// change font of action bar         int titleid = getresources().getidentifier("action_bar_title", "id",             "android");         textview abtitle = (textview) findviewbyid(titleid);         typeface typeface = typeface.createfromasset(getassets(),                 "fonts/lato-regular.ttf");         abtitle.settypeface(typeface);           //this part dynamic based on calculation of ratio          abtitle.settextcolor(getresources().getcolor(r.color.white));         abtitle.setalpha(ratio); 

now have switched material desing , have used appcompat v7: 22+. when run application crashes , gives me nullpointerexception in following line:

abtitle.settypeface(typeface); 

so seems gets id of title cannot find textview

any idea or other ways achieve more appreciated.