Package com.massifmaps.datasources

Class PersistentCacheTileDataSource

java.lang.Object

com.massifmaps.datasources.TileDataSource

com.massifmaps.datasources.CacheTileDataSource

com.massifmaps.datasources.PersistentCacheTileDataSource

public class PersistentCacheTileDataSource
extends CacheTileDataSource

A tile data source that loads tiles from another tile data source
and caches them in an offline sqlite database. Tiles will remain in the database
even after the application is closed.
The database contains table "persistent_cache" with the following fields:
"tileId" (tile id), "compressed" (compressed tile image),
"time" (the time the tile was cached in milliseconds from epoch),
"metaData" (the tile's meta data map as JSON).
Default cache capacity is 50MB.

Constructor Summary

Constructors

Constructor	Description
PersistentCacheTileDataSource(TileDataSource dataSource, String databasePath)	Constructs a PersistentCacheTileDataSource object from tile data source and a sqlite database.

Method Summary

Modifier and Type	Method	Description
void	clear()	Clear the cache.
void	close()	Closes the cache database.
long	getCapacity()	Returns the tile cache capacity.
boolean	isCacheOnlyMode()	Returns the state of cache only mode.
boolean	isOpen()	Returns the status of the cache database.
TileData	loadTile(MapTile mapTile)	Loads the specified tile. Note: the tile coordinate system used here is vertically flipped relative to layer tile coordinate system.
void	setCacheOnlyMode(boolean enabled)	Switches the datasource to 'cache only' mode or switches back from the mode. If enabled, tiles are loaded from the cache only and the original data source is not used. By default, cache only mode is off.
void	setCapacity(long capacityInBytes)	Sets the cache capacity.
void	startDownloadArea(MapBounds mapBounds, int minZoom, int maxZoom, int fetchDelay, TileDownloadListener tileDownloadListener)	Starts downloading the specified area.
void	stopAllDownloads()	Stops all background downloader processes.

Methods inherited from class com.massifmaps.datasources.CacheTileDataSource

getContainerMetaData, getDataExtent, getDataSource, getMaxZoom, getMinZoom, notifyTilesChanged

Methods inherited from class com.massifmaps.datasources.TileDataSource

buildTagValues, containsMetaDataKey, getMaxOverzoomLevel, getMaxZoomWithOverzoom, getMetaData, getMetaDataElement, getProjection, isMaxOverzoomLevelSet, setMaxOverzoomLevel, setMetaData, setMetaDataElement

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

PersistentCacheTileDataSource

public PersistentCacheTileDataSource(TileDataSource dataSource,
 String databasePath)

Constructs a PersistentCacheTileDataSource object from tile data source
and a sqlite database. The sqlite database must be writable, if it doesn't exist, an empty one
will be created instead.

Parameters:

dataSource - The datasource to be cached.

databasePath - The path to the sqlite database, where the tiles will be cached.

Method Details

isCacheOnlyMode

public boolean isCacheOnlyMode()

Returns the state of cache only mode.

Returns:

True when cache only mode is enabled, false otherwise.

setCacheOnlyMode

public void setCacheOnlyMode(boolean enabled)

Switches the datasource to 'cache only' mode or switches back from the mode.
If enabled, tiles are loaded from the cache only and the original data source is not used.
By default, cache only mode is off.

Parameters:

enabled - True when the mode should be enabled, false otherwise.

startDownloadArea

public void startDownloadArea(MapBounds mapBounds,
 int minZoom,
 int maxZoom,
 int fetchDelay,
 TileDownloadListener tileDownloadListener)

Starts downloading the specified area. The area will be stored in the cache.
Note that is the area is too big or cache is already filled, subsequent downloaded tiles
may push existing tile out of the cache.

Parameters:

mapBounds - The bounds of the area to download. The coordinate system of the bounds must be the same as specified in the data source projection.

minZoom - The minimum zoom of the tiles to load.

maxZoom - The maximum zoom of the tiles to load.

fetchDelay - delay between tiles requests. Used to be easy on the servers

tileDownloadListener - The tile download listener to use that will receive download related callbacks.

stopAllDownloads

public void stopAllDownloads()

Stops all background downloader processes.

isOpen

public boolean isOpen()

Returns the status of the cache database.

Returns:

True if the persistent cache database is open and working, false otherwise.

close

public void close()

Closes the cache database. The datasource will still work afterwards,
but all requests will be directed to the original datasource.

loadTile

public TileData loadTile(MapTile mapTile)

Description copied from class: TileDataSource

Loads the specified tile.
Note: the tile coordinate system used here is vertically flipped relative to layer tile coordinate system.

Overrides:

loadTile in class TileDataSource

Parameters:

mapTile - The tile to load.

Returns:

The tile data. If the tile is not available, null may be returned.

clear

public void clear()

Description copied from class: CacheTileDataSource

Clear the cache.

Overrides:

clear in class CacheTileDataSource

getCapacity

public long getCapacity()

Description copied from class: CacheTileDataSource

Returns the tile cache capacity.

Overrides:

getCapacity in class CacheTileDataSource

Returns:

The tile cache capacity in bytes.

setCapacity

public void setCapacity(long capacityInBytes)

Description copied from class: CacheTileDataSource

Sets the cache capacity.

Overrides:

setCapacity in class CacheTileDataSource

Parameters:

capacityInBytes - The new tile cache capacity in bytes.