我正在尝试通过 osmdroid 离线使用 MBtiles，
但总是显示空地图，我的代码有问题吗？
我的代码是：
public class OSMDroid extends AppCompatActivity {
private MapView mapView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_osmdroid);
mapView = (MapView) findViewById(R.id.map);
String name = "map.mbtiles";
File f = new File(Environment.getExternalStorageDirectory() + "/osmdroid", name);
if (f.exists()) {
try {
//ok found a file we support and have a driver for the format, for this demo, we'll just use the first one
//create the offline tile provider, it will only do offline file archives
//again using the first file
OfflineTileProvider tileProvider = new OfflineTileProvider(new SimpleRegisterReceiver(this),
new File[]{f});
//tell osmdroid to use that provider instead of the default rig which is (asserts, cache, files/archives, online
mapView.setTileProvider(tileProvider);
//this bit enables us to find out what tiles sources are available. note, that this action may take some time to run
//and should be ran asynchronously. we've put it inline for simplicity
String source = "";
IArchiveFile[] archives = tileProvider.getArchives();
if (archives.length > 0) {
//cheating a bit here, get the first archive file and ask for the tile sources names it contains
Set<String> tileSources = archives[0].getTileSources();
//presumably, this would be a great place to tell your users which tiles sources are available
if (!tileSources.isEmpty()) {
//ok good, we found at least one tile source, create a basic file based tile source using that name
//and set it. If we don't set it, osmdroid will attempt to use the default source, which is "MAPNIK",
//which probably won't match your offline tile source, unless it's MAPNIK
source = tileSources.iterator().next();
mapView.setTileSource(FileBasedTileSource.getSource(source));
} else {
mapView.setTileSource(TileSourceFactory.DEFAULT_TILE_SOURCE);
}
} else {
mapView.setTileSource(TileSourceFactory.DEFAULT_TILE_SOURCE);
}
mapView.setUseDataConnection(false);
mapView.setBuiltInZoomControls(true);
IMapController mapController = mapView.getController();
mapController.setZoom(10);
GeoPoint startPt = new GeoPoint(61.5797,51.5997);
mapController.setCenter(startPt);
mapView.invalidate();
return;
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
}
MBTilesFileArchive getTileSources 总是返回空字符串，这里是实现：
public Set<String> getTileSources(){
//the MBTiles spec doesn't store source information in it, so we can't return anything
return Collections.EMPTY_SET;
}