How to prioritize thread/Runnable in Android

How to prioritize thread/Runnable in Android

I'm using an AsyncTask to do some task in the background (loading data
from disk) for each row of a ListView. However, when I use TraceView to
see how CPU is shared between my different app threads I end-up with a
case where the main thread consume almost everything and around 70 thread
each one consuming few CPU time. In addition none of these threads seems
to complete as the rows are not redered correctely (data is not loaded).
How could I prioritize the tasks corresponding to visuale rows: complete
the task for a visualize row before running (or after stopping) a task
that corresponds to a hidden row.
Is there a way to do something like using a single thread and prioritizing
the corresponding Runnable instances?