This is a simple application for android using osmdroid 5.6 that show an offline map using downloaded tiles
Clone/download the osmdroid repository: https://github.com/osmdroid/osmdroid
Download and build the osmdroid repository following this page indications: https://github.com/osmdroid/osmdroid/wiki/How-to-build-osmdroid-from-source
After build the projects, see this page in order to use the OSMMapTilePackager https://github.com/osmdroid/osmdroid/tree/master/OSMMapTilePackager
After have obtained the zip you must move it to the sdcard/osmdroid folder on your device