Android :: Which UI Approach Is Better?

I'm navigating through a 3-level hierarchy of names to get to a document view page. I've set up tabs for the 3 levels. The tabs are left, middle, and right where the right tab is the lowest level of the hierarchy. Each tab has a list of 10 to 20 Radio Buttons with the names. This all works great and is very efficient and intuitive. One note is that there may be 1000 documents available (from an online source) but the average user will only be viewing a handful regularly. So I store the choices for each of the 3 tabs. This way a user can quickly navigate to his favorite without having to negotiate the entire hierarchy each time. My question comes when the user is on the right tab. At this point they have navigated through to the document they want and I'm wondering what is the best way to initiate the document view page. Remember that most of the navigation happens on the right tab in the small set of documents the user regularly visits, with only occasional visits to the other tabs. So making the right tab efficient is good. My current approach is to add a LongClickListener to the buttons of the right tab. Then a press-and-hold kicks off the document view. This certainly minimizes the number of objects on the screen and the number of separate clicks required to get to the document but I question whether new users will know that a long press is expected. I guess I could put up some Toast if the user doesn't do anything for 5 seconds but that still seems clunky. Another approach is to add a Button at the top of the right tab Radio Buttons. This has the merit of being dead obvious but it's a less efficient use of screen space and also an extra click for an experienced user.