GIS的学习（四十二）osmdroid基于离线地图的几种格式

      在osmdroid中支持多种离线地图格式，其中sqlite，mbtiles，zip，gemf等格式，那么他们的格式有什么不同呢？

下面我们慢慢来研究一下源代码既可以知道。

 

针对ArchiveFileFactory的类查看如下：

package org.osmdroid.tileprovider.modules;

import java.io.File;
import java.io.IOException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import android.database.sqlite.SQLiteException;

public class ArchiveFileFactory {

	private static final Logger logger = LoggerFactory.getLogger(ArchiveFileFactory.class);

	/**
	 * Return an implementation of {@link IArchiveFile} for the specified file.
	 * @return an implementation, or null if there's no suitable implementation
	 */
	public static IArchiveFile getArchiveFile(final File pFile) {

		if (pFile.getName().endsWith(".zip")) {
			try {
				return ZipFileArchive.getZipFileArchive(pFile);
			} catch (final IOException e) {
				logger.error("Error opening ZIP file", e);
			}
		}

		if (pFile.getName().endsWith(".sqlite")) {
			try {
				return DatabaseFileArchive.getDatabaseFileArchive(pFile);
			} catch (final SQLiteException e) {
				logger.error("Error opening SQL file", e);
			}
		}

		if (pFile.getName().endsWith(".mbtiles")) {
			try {
				return MBTilesFileArchive.getDatabaseFileArchive(pFile);
			} catch (final SQLiteException e) {
				logger.error("Error opening MBTiles SQLite file", e);
			}
		}
		
		if (pFile.getName().endsWith(".gemf")) {
			try {
				return GEMFFileArchive.getGEMFFileArchive(pFile);
			} catch (final IOException e) {
				logger.error("Error opening GEMF file", e);
			}
		}

		return null;
	}

}

 

其中sqlite格式如下：存储的表名为：tiles字段为tile，key,provider,

具体实现如下：

package org.osmdroid.tileprovider.modules;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.InputStream;

import org.osmdroid.tileprovider.MapTile;
import org.osmdroid.tileprovider.tilesource.ITileSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;

public class DatabaseFileArchive implements IArchiveFile {

	private static final Logger logger = LoggerFactory.getLogger(DatabaseFileArchive.class);

	private final SQLiteDatabase mDatabase;

	private DatabaseFileArchive(final SQLiteDatabase pDatabase) {
		mDatabase = pDatabase;
	}

	public static DatabaseFileArchive getDatabaseFileArchive(final File pFile) throws SQLiteException {
		return new DatabaseFileArchive(SQLiteDatabase.openOrCreateDatabase(pFile, null));
	}

	@Override
	public InputStream getInputStream(final ITileSource pTileSource, final MapTile pTile) {
		try {
			InputStream ret = null;
			final String[] tile = {"tile"};
			final long x = (long) pTile.getX();
			final long y = (long) pTile.getY();
			final long z = (long) pTile.getZoomLevel();
			final long index = ((z << z) + x << z) + y;
			final Cursor cur = mDatabase.query("tiles", tile, "key = " + index + " and provider = '" + pTileSource.name() + "'", null, null, null, null);
			if(cur.getCount() != 0) {
				cur.moveToFirst();
				ret = new ByteArrayInputStream(cur.getBlob(0));
			}
			cur.close();
			if(ret != null) {
				return ret;
			}
		} catch(final Throwable e) {
			logger.warn("Error getting db stream: " + pTile, e);
		}

		return null;
	}

	@Override
	public String toString() {
		return "DatabaseFileArchive [mDatabase=" + mDatabase.getPath() + "]";
	}

}

 

格式为mbtiles的数据结构：

//	TABLE tiles (zoom_level INTEGER, tile_column INTEGER, tile_row INTEGER, tile_data BLOB);
	public final static String TABLE_TILES = "tiles";
	public final static String COL_TILES_ZOOM_LEVEL = "zoom_level";
	public final static String COL_TILES_TILE_COLUMN = "tile_column";
	public final static String COL_TILES_TILE_ROW = "tile_row";
	public final static String COL_TILES_TILE_DATA = "tile_data";

 具体实现：

package org.osmdroid.tileprovider.modules;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.InputStream;

import org.osmdroid.tileprovider.MapTile;
import org.osmdroid.tileprovider.tilesource.ITileSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;

public class MBTilesFileArchive implements IArchiveFile {

	private static final Logger logger = LoggerFactory.getLogger(MBTilesFileArchive.class);

	private final SQLiteDatabase mDatabase;

	//	TABLE tiles (zoom_level INTEGER, tile_column INTEGER, tile_row INTEGER, tile_data BLOB);
	public final static String TABLE_TILES = "tiles";
	public final static String COL_TILES_ZOOM_LEVEL = "zoom_level";
	public final static String COL_TILES_TILE_COLUMN = "tile_column";
	public final static String COL_TILES_TILE_ROW = "tile_row";
	public final static String COL_TILES_TILE_DATA = "tile_data";

	private MBTilesFileArchive(final SQLiteDatabase pDatabase) {
		mDatabase = pDatabase;
	}

	public static MBTilesFileArchive getDatabaseFileArchive(final File pFile) throws SQLiteException {
		return new MBTilesFileArchive(
				SQLiteDatabase.openDatabase(
						pFile.getAbsolutePath(),
						null,
						SQLiteDatabase.NO_LOCALIZED_COLLATORS | SQLiteDatabase.OPEN_READONLY));
	}

	@Override
	public InputStream getInputStream(final ITileSource pTileSource, final MapTile pTile) {
		try {
			InputStream ret = null;
			final String[] tile = { COL_TILES_TILE_DATA };
			final String[] xyz = {
					  Integer.toString(pTile.getX())
					, Double.toString(Math.pow(2, pTile.getZoomLevel()) - pTile.getY() - 1)  // Use Google Tiling Spec
					, Integer.toString(pTile.getZoomLevel())
			};

			final Cursor cur = mDatabase.query(TABLE_TILES, tile, "tile_column=? and tile_row=? and zoom_level=?", xyz, null, null, null);

			if(cur.getCount() != 0) {
				cur.moveToFirst();
				ret = new ByteArrayInputStream(cur.getBlob(0));
			}
			cur.close();
			if(ret != null) {
				return ret;
			}
		} catch(final Throwable e) {
			logger.warn("Error getting db stream: " + pTile, e);
		}

		return null;
	}

	@Override
	public String toString() {
		return "DatabaseFileArchive [mDatabase=" + mDatabase.getPath() + "]";
	}

}

 

 

GEMF文件格式的：

     GEMF格式的文件存储算法比较复杂，但是据说为加载最快的方式。

package org.osmdroid.tileprovider.modules;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

import org.osmdroid.tileprovider.MapTile;
import org.osmdroid.tileprovider.tilesource.ITileSource;
import org.osmdroid.util.GEMFFile;

public class GEMFFileArchive implements IArchiveFile {

	private final GEMFFile mFile;

	private GEMFFileArchive(final File pFile) throws FileNotFoundException, IOException {
		mFile = new GEMFFile(pFile);
	}

	public static GEMFFileArchive getGEMFFileArchive(final File pFile) throws FileNotFoundException, IOException {
		return new GEMFFileArchive(pFile);
	}

	@Override
	public InputStream getInputStream(final ITileSource pTileSource, final MapTile pTile) {
		return mFile.getInputStream(pTile.getX(), pTile.getY(), pTile.getZoomLevel());
	}

	@Override
	public String toString() {
		return "GEMFFileArchive [mGEMFFile=" + mFile.getName() + "]";
	}

}

   

 ZIP格式：

 

package org.osmdroid.tileprovider.modules;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipException;
import java.util.zip.ZipFile;

import org.osmdroid.tileprovider.MapTile;
import org.osmdroid.tileprovider.tilesource.ITileSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ZipFileArchive implements IArchiveFile {

	private static final Logger logger = LoggerFactory.getLogger(ZipFileArchive.class);

	private final ZipFile mZipFile;

	private ZipFileArchive(final ZipFile pZipFile) {
		mZipFile = pZipFile;
	}

	public static ZipFileArchive getZipFileArchive(final File pFile) throws ZipException, IOException {
		return new ZipFileArchive(new ZipFile(pFile));
	}

	@Override
	public InputStream getInputStream(final ITileSource pTileSource, final MapTile pTile) {
		final String path = pTileSource.getTileRelativeFilenameString(pTile);
		try {
			final ZipEntry entry = mZipFile.getEntry(path);
			if (entry != null) {
				return mZipFile.getInputStream(entry);
			}
		} catch (final IOException e) {
			logger.warn("Error getting zip stream: " + pTile, e);
		}
		return null;
	}

	@Override
	public String toString() {
		return "ZipFileArchive [mZipFile=" + mZipFile.getName() + "]";
	}

}

 

 

 

实现：最初显示”中国地图（省界）“，放大到一定程度显示”中国地图（地市分界）“，继续放大切换到Google街道地图。

 

 

<!DOCTYPE html>
<html>
	<head>
		<title>中国地图</title>
		<meta http-equiv="content-type" content="text/html; charset=UTF-8">
		<link rel="stylesheet" href="css/style.css" type="text/css" />
		<style type="text/css" media="screen">
			body {
				margin:0;
				padding:0;
				height:100%; 
			}
			.bigmap {
				position:absolute;
				left:0;
				top:0px;
				padding:0;
				width:100%;
				height:100%; 
				border:1px solid #333;
			}
		</style>
		<script type="text/javascript" src="js/OpenLayers/lib/OpenLayers.js"></script>
		<script src="http://maps.google.com/maps/api/js?v=3.6&amp;sensor=false"></script>
		<script type="text/javascript">
			var map, layer_province, layer_city, layer_street, vlayer;
			
			// 第一次打开地图的中心位置（经度、纬度）
			var firstLon = 109.33981;
			var firstLat = 33.72419;
			
			/*
			 * 切换地图比例尺设置
			 *	scale1：
			 *  scale2: 省地图和地市地图切换点
			 *  scale3: 地市地图和谷歌街道地图切换点
			 */
			var scale1 = 20000000;
			var scale2 = 10000000;
			var scale3 = 2000000;
			
			var level1 = 1;
			var level2 = 2;
			var level3 = 3;
			var level = level1;
			
				
			function init() {
				// 创建MAP DIV框架
				map = new OpenLayers.Map("map",
					{
						maxResolution: 'auto',
						maxExtent: new OpenLayers.Bounds(
							73.44696044921875, 6.318641185760498, 
							135.08583068847656, 53.557926177978516),
						displayProjection: new OpenLayers.Projection("EPSG:4326")
					});
				
				// 增加中国地图(省界) Layer
				addProvinceLayer()
				
				// 增加中国地图(地市分界) Layer
				addCityLayer();
				
				// 增加Google Street Layer
				addStreetLayer();
				
				// 增加地图Layer切换Register
				addMapRegister();
				
				map.zoomToMaxExtent();
				map.setCenter(new OpenLayers.LonLat(firstLon, firstLat), 0);
				
				map.addControl(new OpenLayers.Control.Scale());
				map.addControl(new OpenLayers.Control.MousePosition());
				map.addControl(new OpenLayers.Control.LayerSwitcher());
			}
			
			function addProvinceLayer() {
				layer_province = new OpenLayers.Layer.WMS(
				    "China:province", "http://10.0.0.239:8081/geoserver/wms",
				    {
				    	layers: "China:province",
				    },
				    {
				    	singleTile: true, //set single label
				    	isBaseLayer: true,
				    	projection: "EPSG:4326",
				    	maxExtent: new OpenLayers.Bounds(
				    		73.44696044921875, 6.318641185760498, 
				    		135.08583068847656, 53.557926177978516)
				    }
				);
				map.addLayer(layer_province);
			}
			
			function addCityLayer() {
				layer_city = new OpenLayers.Layer.WMS(
				    "China:city", "http://10.0.0.239:8081/geoserver/wms",
				    {
				    	layers: "China:city"
				    },
				    {
				    	singleTile: true, //set single label
				    	visibility: false,
				    	projection: "EPSG:4326",
				    	displayInLayerSwitcher: false,
				    	maxExtent: new OpenLayers.Bounds(
				    		73.44696044921875, 6.318641185760498, 
				    		135.08583068847656, 53.557926177978516)
				    }
				);
				map.addLayer(layer_city);
			}
			
			function addStreetLayer() {
				layer_street = new OpenLayers.Layer.Google(
				    "Google Streets", // the default
				    {
				    	numZoomLevels: 18 ,
				    	projection: "EPSG:900913",
				    	visibility: false,
				    	displayInLayerSwitcher: false,
				    	maxExtent: new OpenLayers.Bounds(
				    		-128 * 156543.03390625,
				    		-128 * 156543.03390625,
				    		128 * 156543.03390625,
				    		128 * 156543.03390625)
				    }
				);
				map.addLayer(layer_street);
			}
			
			function addMapRegister(){
				map.events.register("zoomend", map, function(){
					var cur_scale = map.getScale();
					if(cur_scale >= scale2) {
						if(level != level1) {
						    
						    if(level == level2) {
								map.setCenter(map.center.transform(
							       new OpenLayers.Projection("EPSG:4326"),
							       new OpenLayers.Projection("EPSG:4326")
							    ), map.getZoom());
							} else {
								map.setCenter(map.center.transform(
							       new OpenLayers.Projection("EPSG:900913"),
							       new OpenLayers.Projection("EPSG:4326")
							    ), map.getZoom());
							}
						    
						    level = level1;
						    
						    layer_province.displayInLayerSwitcher = true;
							layer_city.displayInLayerSwitcher = false;
							layer_street.displayInLayerSwitcher = false;
							
							map.setBaseLayer(layer_province);
							layer_city.setVisibility(false);
							layer_street.setVisibility(false);
							
						}
					} else if(cur_scale < scale2 && cur_scale >= scale3){
						if(level != level2){
							if(level == level1) {
								map.setCenter(map.center.transform(
							       new OpenLayers.Projection("EPSG:4326"),
							       new OpenLayers.Projection("EPSG:4326")
							    ), map.getZoom());
							} else {
								map.setCenter(map.center.transform(
							       new OpenLayers.Projection("EPSG:900913"),
							       new OpenLayers.Projection("EPSG:4326")
							    ), map.getZoom());
							}
						    
						    level = level2;
						    
						    layer_province.displayInLayerSwitcher = false;
							layer_city.displayInLayerSwitcher = true;
							layer_street.displayInLayerSwitcher = false;
							
							map.setBaseLayer(layer_city);
							layer_province.setVisibility(false);
							layer_street.setVisibility(false);
							
						}
					} else if(cur_scale < scale3){
					   	if(level != level3) {
							map.setCenter(map.center.transform(
						        new OpenLayers.Projection("EPSG:4326"),
						        new OpenLayers.Projection("EPSG:900913")
						    ), map.getZoom());
						    
						    level = level3;
						    
						    layer_province.displayInLayerSwitcher = false;
							layer_city.displayInLayerSwitcher = false;
							layer_street.displayInLayerSwitcher = true;
							
							map.setBaseLayer(layer_street);
							layer_city.setVisibility(false);
							layer_province.setVisibility(false);
							
					    }
					} 
				});
			}
		</script>
	</head>

	<body onload="init()" >
		<div id="map" class="bigmap"></div>
	</body>
</html>

 

参考：

add, remove base layers depending on zoom, change baselayer

Zoom Control Example