I am not sure what's the means of vector tile and raster tile here, because I think for cached tile, it only should be vector. The raster only works for some special data format like JP2, ecw etc.
If you want to make the layer render on user's mobile, you should want to provide the shape file and then it can be rendered there, but I think more popular solution should be build cache tile images on server side, then zip them by city and let user choose to download it for offline works. In fact the Bing, Google tiles is this mode, it only provide the existing tiles but not data file for render, so the problem here should be how to generate the tile on server side and render then on mobile side.
We have a utility CacheGenerator, you should can find it on our wiki.thinkgeo.com, I hadn't tested whether it can works well with Android edition, but I think you can have a try.
Wish that's helpful.