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I am planning to build sort of a geography quiz app where you have to touch inside the borders of the searched country. So, I have to display a map (I want it to be offline) and be able to test the user click against the map in some way.

I've been searching a while now and found good OSM material from Natural Earth Data and TileMill for converting it to a MBTiles-file (sqlite-database containing all the png's and some meta-data too (using UTFGrid)).

On the Android-side, I would like to use OSMdroid for displaying the maps, mainly because it's open-source and highly maintained.

I've found some guides on how to use the MBTiles-database inside osmdroid but is there also an easy way to access the metadata or check otherwise if the user touched inside the right country area? I would like to avoid some sort of "boundary boxes"...

Any help is highly appreciated!

mikolaiguetschow
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1 Answers1

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I'm pretty sure that bounding box calculation is best option.

Can you access metadata from the offline tile source? Yes, kind of. You can get a list of unique tile sources in the archive but that's it. There's an open issue regarding getting the bounds of a given offline archive. You can follow it here (or contribute)

https://github.com/osmdroid/osmdroid/issues/174

It's slightly complex because offline tiles are going to have a bounds per layer/source and per zoom level. There's also no guarantee that that bounds of that given zoom/layer is going to be contiguous. I.E. one zoom level can have both the US and western Europe in it.

spy
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