AdAway uses a Mobile Hosts file of sorts - I'm not quite sure if this is what you might be looking for. http://sufficientlysecure.org/index.php/adaway/ Requires a Rooted phone and a one-time use of a download from "Untrusted Sources" as the app is not available via Google Play.
You could always setup something like OpenDNS and block pornography at a router level. Of course there are ways around this by either disconnecting the wireless network or turning it off. It would also be necessary for you to have a wireless router in place that your phone connects to.
K9 Web Protection Browser for Android - https://play.google.com/store/apps/details?id=com.bluecoat.k9.android
You can use k9 web browser or other similar browsers and lock all other browsers using an app lock program that may be found in play store. Do take note of the permissions asked by the apps. Forticlient has a vpn app for android which has web filtering capabilities. But it is easy to disable. If your phone is rooted you can change your dns to open dns or Norton dns. But they may be ineffective (I am not sure) if you use browsers like opera mini which direct all their traffic to their servers for compression purposes.
The norton dns is stoping the porn site, very good. Whole area covered with router rule of not to accpet outgoing port 53 unless intentions of it being norton ip address. Forces noton dns to exist. Not way around this. Norton does the block of site, as if it were www pornsite dot com. but also can get around of this by site that returns site! Google search the image of porn (or what topic you use) and image can be shown! So noton does that stopping well, only that google safe searching not to be locked in and can still full get some porn. Bing can honor safe search better but not as bing is like the google as much, but needs can dictite what you would use. Norton works good then if not knowing about way to surround it like with google. Maybe also router can forward 53 isp to 53 norton, create invisible fix?