Android TabHost, ListView and Fragments, populated using AsyncTask

I need a simple example Android project that has: a) A screen that has a ComboBox that is populated using AsyncTask, under this a TabHost, that has 3 tabs. Each of these TabViews has a ListView with a custom view that has a CheckBox and TextView. The ListView items need to get populated from an AsyncTask when the tab comes into focus. For the items please just populate the ListView with static ArrayList content inside the doInBackground method. I would like this initial request to get 20 objects (for example), but when the list is scrolled follow to the bottom it can do another AsyncRequest and get another 20 items and append them to the bottom of the results, and then call's notifyDataSetChanged in the MediaAdapter? Or if there is a better way to do this please explain. Please see mock up screens provided. I would need this project within 48 hours. Any questions please ask. Regards Phil