Loading tiles from the assets directory.

[GoogleCodeExporter]

Help request.

I am trying to load map tiles from the assets directory.

I see the I need to write a custom TileProvider, but am unsure where to go next:

The existing tile loaders make assumptions that the tile is coming from a URL 
or File, and the themselves translate into an InputStream. Unfortunately, the 
android.content.res.AssetManager can only give FileDescriptors and InputStreams.

This makes me think I need to write my own MapTileModuleProviderBase? 

Is this something likely to be supported in future?

** Design Critique; please ignore. ** 
** Likely due to lack of clarity in my own head. **
It's a shame that all the translating from Tile to InputStream can't be done in 
a single method on TileSource, then all Executors/ThreadPool etc can be done in 
a more generic TileLoader and MapTileProvider
** End of Design Critique **

Thanks. 

Original issue reported on code.google.com by gullcatc...@gmail.com on 26 Feb 2011 at 11:58

[GoogleCodeExporter]

The TileSource classes are designed to mostly encapsulate meta-data about the 
tile source and the MapTileModule classes are designed to do the work of 
pulling the data described by the TileSource. Your situation does probably call 
for creating a MapTileModule that does the work of pulling the data from the 
assets. You should probably extend BitmapTileSourceBase. It would likely ignore 
calls to setTileSource (unless the assets contains different tile sets). If you 
have recommendations for changes to the API to make this more generic without 
losing any current functionality, then we'd be happy to take a look!

Original comment by kurtzm...@gmail.com on 27 Feb 2011 at 4:27

• Added labels: Type-Enhancement
• Removed labels: Type-Defect

[GoogleCodeExporter]

It should be possible to read zip and gemf files from the assets directory.

Original comment by neilboyd on 17 Mar 2011 at 3:32

• Changed state: Accepted

[GoogleCodeExporter]

Attached is a patch that implements this.
It only works for GEMF files because that's the only type of archive where I 
can influence the reading from file to also be able to handle reading from 
assets.

I'd appreciate any feedback, especially from the people that implemented GEMF 
and the tile provider.

Also attached is the GEMF that should be placed in assets.

Original comment by neilboyd on 29 Mar 2011 at 10:01

• Changed state: Started

Attachments:

• issue169.patch
• haarlem.gemf

[GoogleCodeExporter]

Has this issue been integrated into the code? Or should I download and apply it 
by myself?

Original comment by zetxek on 13 Jun 2011 at 10:22

[GoogleCodeExporter]

No it hasn't been integrated. I asked for feedback and didn't get any.

Original comment by neilboyd on 14 Jun 2011 at 4:58

[GoogleCodeExporter]

I really find this a quite interesting feature to have, as this way you don't 
need to have the maps on the SD card... I will surely download osmdroid source 
code and try your patch and give some feedback!

Original comment by zetxek on 14 Jun 2011 at 8:08

[GoogleCodeExporter]

Greetings,

Not sure if this thread is still alive. I came upon it when looking for 
information about using the assets folder to store tiles in.
Upon reading here, I downloaded and applied issue169.patch. Successfully 
testing it with haarlem.gemf, I converted the Osmdroid.zip file to gemf and put 
them into my assets folder. When launching the app, it failed to load the map 
with following error:

D/szipinf ( 1827): Initializing inflate state
E/o*.o*.t*.m*.ArchiveFil*( 1827): Error opening GEMF file
E/o*.o*.t*.m*.ArchiveFil*( 1827): java.io.FileNotFoundException: This file can 
not be opened as a file descriptor; it is probably compressed

I then put my gemf file in the original /sdcard/osmdroid folder and read it 
from there, with positive result. I could successfully view and zoom the map.
Since I have zoom levels down to 18, I recreated the map file(gemf) with lowest 
zoom level only and added it back to the assets folder. The map loaded nicely. 
I kept recreating the gemf with added zoom levels. Once reaching level 14, it 
crashed again with above exception. I removed zoom level 14 and added 15, 
causing the crash again. This happened for all zoom levels between 14-18. 
For above tests, I was using the CloudMade map source, but I also tested it 
using Mapnik, with same results, although I only had zoom levels to 16 there. 
The map always started failing for zoom level 14 and above.

Not sure why it kept crashing on high zooms, I tested creating a new gemf file 
from a random different area, and here it would work just fine all the way up 
to 18.

Was wondering if anyone have ideas of what may cause this problem? Perhaps I am 
using an incorrect method of creating the gemf files, though it seems to work 
for some places. 
Worst case, I can always go back to using the osmdroid folder, but I think 
being able to load maps from assets is a nice feature.

Some info in no particular order:
* patch issue169.patch added to checkout of 
http://osmdroid.googlecode.com/svn/trunk
    Revision: 1082
* Tried with CloudMade Default Style and Mapnik from mobac(no errors reported 
during download/creation), zoom levels 10 - 18. Map fails to load from zoom 
level 14 with both formats
* Atlas format used: Osmdroid ZIP
* gemf file conversion: unzip archive and run generate_efficient_map_file.py 
(kept getting a java.lang.NoClassDefFoundError: Could not initialize class 
org.osmdroid.tileprovider.util.StreamUtils when trying osmdroid-packager).

Here is the full trace:

D/GEMFFileArchive( 1827): constructor
D/GEMFFileArchive( 1827): constructor
D/GEMFFileArchive( 1827): constructor
D/szipinf ( 1827): Initializing inflate state
E/o*.o*.t*.m*.ArchiveFil*( 1827): Error opening GEMF file
E/o*.o*.t*.m*.ArchiveFil*( 1827): java.io.FileNotFoundException: This file can 
not be opened as a file descriptor; it is probably compressed
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.content.res.AssetManager.openAssetFd(Native Method)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.content.res.AssetManager.openFd(AssetManager.java:330)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.util.GEMFFile.getLength(GEMFFile.java:521)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.util.GEMFFile.readHeader(GEMFFile.java:465)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.util.GEMFFile.<init>(GEMFFile.java:96)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.util.GEMFFile.<init>(GEMFFile.java:83)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.tileprovider.modules.GEMFFileArchive.<init>(GEMFFileArchive.java:27
)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.tileprovider.modules.GEMFFileArchive.getGEMFFileArchive(GEMFFileArc
hive.java:31)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.tileprovider.modules.ArchiveFileFactory.getArchiveFile(ArchiveFileF
actory.java:54)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.tileprovider.modules.MapTileAssetsArchiveProvider.findArchiveFiles(
MapTileAssetsArchiveProvider.java:86)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.tileprovider.modules.MapTileAssetsArchiveProvider.<init>(MapTileAss
etsArchiveProvider.java:35)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
org.osmdroid.samples.SampleWithTilesInAssets.onCreate(SampleWithTilesInAssets.ja
va:27)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.app.ActivityThread.access$1500(ActivityThread.java:117)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.os.Handler.dispatchMessage(Handler.java:99)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at android.os.Looper.loop(Looper.java:123)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
android.app.ActivityThread.main(ActivityThread.java:3683)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
java.lang.reflect.Method.invokeNative(Native Method)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
java.lang.reflect.Method.invoke(Method.java:507)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at 
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E/o*.o*.t*.m*.ArchiveFil*( 1827):   at dalvik.system.NativeStart.main(Native 
Method)

Thanks

Original comment by hja...@gmail.com on 29 Mar 2012 at 5:45