NPE in when databaseIndexCache is still null

[gknisely]

@devemux86 or can someone check this logic. This seems to fix NPE when databaseIndexCache is still null, but I was concerned that I could introduce more issues.

If this looks good, I will PR the changes.

Logs:

06-18 07:59:55.093  2397  4018 E MapFile : java.lang.NullPointerException: Attempt to invoke virtual method 'long org.oscim.tiling.source.mapfile.IndexCache.getIndexEntry(org.oscim.tiling.source.mapfile.header.SubFileParameter, long)' on a null object reference
06-18 07:59:55.093  2397  4018 E MultiMapFile: java.lang.NullPointerException: Attempt to read from field 'org.oscim.core.BoundingBox org.oscim.tiling.source.mapfile.MapInfo.boundingBox' on a null object reference
06-18 07:59:55.109  2397  4017 E MapFile : java.lang.NullPointerException: Attempt to invoke virtual method 'long org.oscim.tiling.source.mapfile.IndexCache.getIndexEntry(org.oscim.tiling.source.mapfile.header.SubFileParameter, long)' on a null object reference
06-18 07:59:55.109  2397  4017 E MultiMapFile: java.lang.NullPointerException: Attempt to read from field 'org.oscim.core.BoundingBox org.oscim.tiling.source.mapfile.MapInfo.boundingBox' on a null object reference
06-18 07:59:55.144  2397  4019 E MapFile : java.lang.NullPointerException: Attempt to invoke virtual method 'long org.oscim.tiling.source.mapfile.IndexCache.getIndexEntry(org.oscim.tiling.source.mapfile.header.SubFileParameter, long)' on a null object reference
06-18 07:59:55.144  2397  4019 E MultiMapFile: java.lang.NullPointerException: Attempt to read from field 'org.oscim.core.BoundingBox org.oscim.tiling.source.mapfile.MapInfo.boundingBox' on a null object reference
06-18 07:59:55.155  2397  4020 E MapFile : java.lang.NullPointerException: Attempt to invoke virtual method 'long org.oscim.tiling.source.mapfile.IndexCache.getIndexEntry(org.oscim.tiling.source.mapfile.header.SubFileParameter, long)' on a null object reference
06-18 07:59:55.155  2397  4020 E MultiMapFile: java.lang.NullPointerException: Attempt to read from field 'org.oscim.core.BoundingBox org.oscim.tiling.source.mapfile.MapInfo.boundingBox' on a null object reference

[devemux86]

@gknisely Thanks for the report.

How does it happen? Can it be reproduced?

The databaseIndexCache is written in open and gets null in close.

[gknisely]

sure checking

[gknisely]

Still digging into this as time permits. I will let you know what I find.

[gknisely]

Seems that the culprit here is that while maps are still being rendered, ondestroy() is called. We have an Android app that is using MultiMapFileTileSource and it seems the queue of map tiles to render is not cleared and pending tile rendering tasks happen after destroying the mapview. If we do wait until all rendering of the maps is complete, the exceptions do not happen. So basically not all of the map files are loaded/rendered yet, but the user cancels the map drawing before it is finished. Any ideas on things to try?

[devemux86]

@gknisely You probably mean the MapFileTileSource.close method.

A proper solution would be to stop the use / render of map file when calling close.
I don't know how or if this is possible.

Perhaps you could improve how you're using the API?
Or simply add a null check like you suggested.

[gknisely]

@devemux86 ok thank you for your help.