Android: Scrolling to slow on gridview?

Android: Scrolling to slow on gridview?

i have trouble to speed up the scrolling on gridview when I show the
thumbnail on the phone with getThumbnail. I know it's create a thumbnail
if not existed. I think of using AsyncTask to create the thumbnail in the
background. In my knowledge we can only have limited parallel execution of
the AsyncTask.
Does anyone know how to create a smooth scrollable gridvie? Please help.
Using cache is good but only if the thumbnail has been cached, but it
won't give a smooth scrolling for the new data.