概述:

经过一个春节的休整,今天最终開始了!

任何时候。都不要忘记学习。学习是一辈子的事情!今天,我来说说怎样实现天地图的离线以及Openlayers载入离线数据实现天地图数据的展示。


实现:

1、获取天地图的数据

能够通过网络上下载各大地图的工具将天地图的数据下载下来。并制作成mbtiles文件。制作过程在此就不详述,将已经制作好的一个文件上传到了百度网盘。须要的童鞋能够下载哦~~~~

下载链接:http://pan.baidu.com/s/1dEmNtnF password:xqd8


2、读取mbtiles并返回到页面

mbtiles事实上就是一个sqllite数据库, 其具体可移步至http://www.cnblogs.com/i-gps/p/3919475.html查看具体。

在此方案中,我用了一个servlet。具体的实现代码例如以下:

package com.lzugis.web;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Created by Administrator on 2016/2/27.
 */
@WebServlet(description = "tian ditu tile", urlPatterns =  {"/tdttile"})
public class TiandituTile extends HttpServlet {
    private String tilepath = "D:/data/tdt/";
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String tile_column = request.getParameter("X");
        String tile_row = request.getParameter("Y");
        String zoom_level = request.getParameter("L");
        String layer = request.getParameter("T");
        // TODO Auto-generated method stub
        try {
            Class.forName("org.sqlite.JDBC");
        }
        catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            // e.printStackTrace();
            System.out.println("数据库驱动未找到!");
        }
        // 得到连接 会在你所填写的文件夹建一个你命名的文件数据库
        Connection conn;
        try {
            String conurl = "jdbc:sqlite:"+tilepath+layer+".mbtiles";
            conn = DriverManager.getConnection(conurl,null,null);
            // 设置自己主动提交为false
            conn.setAutoCommit(false);
            Statement stmt = conn.createStatement();
            //推断表是否存在
            ResultSet rsTables = conn.getMetaData().getTables(null, null, "tiles", null);
            if(!rsTables.next()){
                System.out.println("表不存在");
            }
            // 得到结果集
            String sql = "SELECT * FROM tiles WHERE zoom_level = "+zoom_level+
                    " AND tile_column = "+tile_column+
                    " AND tile_row = "+tile_row;
            ResultSet rs = stmt.executeQuery(sql);
            if(rs.next()) {
                byte[] imgByte = (byte[]) rs.getObject("tile_data");
                InputStream is = new ByteArrayInputStream(imgByte);
                OutputStream os = response.getOutputStream();
                try {
                    int count = 0;
                    byte[] buffer = new byte[1024 * 1024];
                    while ((count = is.read(buffer)) != -1) {
                        os.write(buffer, 0, count);
                    }
                    os.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    os.close();
                    is.close();
                }
            }
            else{
                System.out.println(sql);
                System.out.println("未找到图片!

"); } rs.close(); conn.close(); } catch (SQLException e) { e.printStackTrace(); System.out.println("SQL异常!"); } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }

当中,请求地址为:http://localhost:8081/lzugis/tdttile?

T=vec_c&L=5&X=25&Y=3。请求的结果例如以下所看到的:



3、openlayers调用

从网上拔了下openlayers载入天地图的代码。并稍作改动。扩展了一个openlayers图层TiandituLayer。其代码例如以下:

OpenLayers.Layer.TiandituLayer = OpenLayers.Class(OpenLayers.Layer.Grid,{
	mapType : null,
	mirrorUrls : null,
	topLevel : null,
	bottomLevel : null,
	
	//用于标识是本地天地图切片库还是訪问在线天地图
	isOnline:true,

	topLevelIndex : 0,
	bottomLevelIndex : 20,
	topTileFromX : -180,
	topTileFromY : 90,
	topTileToX : 180,
	topTileToY : -270,

	isBaseLayer : true,

	initialize : function(name, url, options) {
		options.topLevel = options.topLevel ? options.topLevel
				: this.topLevelIndex;
		options.bottomLevel = options.bottomLevel ?

options.bottomLevel : this.bottomLevelIndex; options.maxResolution = this .getResolutionForLevel(options.topLevel); options.minResolution = this .getResolutionForLevel(options.bottomLevel); var newArguments = [ name, url, {}, options ]; OpenLayers.Layer.Grid.prototype.initialize.apply(this, newArguments); }, clone : function(obj) { if (obj == null) { obj = new OpenLayers.Layer.TiandituLayer(this.name, this.url, this.options); } obj = OpenLayers.Layer.Grid.prototype.clone .apply(this, [ obj ]); return obj; }, getURL : function(bounds) { var level = this.getLevelForResolution(this.map.getResolution()); var coef = 360 / Math.pow(2, level); var x_num = this.topTileFromX < this.topTileToX ?

Math .round((bounds.left - this.topTileFromX) / coef) : Math .round((this.topTileFromX - bounds.right) / coef); var y_num = this.topTileFromY < this.topTileToY ?

Math .round((bounds.bottom - this.topTileFromY) / coef) : Math.round((this.topTileFromY - bounds.top) / coef); var type = this.mapType; var url = this.url; if (this.mirrorUrls != null) { url = this.selectUrl(x_num, this.mirrorUrls); } return this.getFullRequestString({ T : type, X : x_num, Y : y_num, L : level }, url); }, getFullRequestString: function(params, url){ url = url+'?T='+params.T+'&L='+params.L+'&X='+params.X+'&Y='+params.Y; return url; }, selectUrl : function(a, b) { return b[a % b.length] }, getLevelForResolution : function(res) { var ratio = this.getMaxResolution() / res; if (ratio < 1) return 0; for ( var level = 0; ratio / 2 >= 1;) { level++; ratio /= 2; } return level; }, getResolutionForLevel : function(level) { return 360 / 256 / Math.pow(2, level); }, getMaxResolution : function() { return this.getResolutionForLevel(this.topLevelIndex) }, getMinResolution : function() { return this.getResolutionForLevel(this.bottomLevelIndex) }, CLASS_NAME : "OpenLayers.Layer.TiandituLayer" });

在代码中新建一个TiandituLayer。并加入到map中就可以实现,代码例如以下:

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <title>OpenLayers MapQuest Demo</title>
    <link rel="stylesheet" href="../../../../plugin/OpenLayers-2.13.1/theme/default/style.css" type="text/css">
    <script src="../../../../plugin/OpenLayers-2.13.1/OpenLayers.js"></script>
    <script src="TiandituLayer-src.js"></script>
    <style type="text/css">
        html, body, #map{
            padding:0;
            margin:0;
            height:100%;
            width:100%;
            overflow: hidden;
        }
    </style>
    <script type="text/javascript">
        var map;
        function init(){
            var vec_c = new OpenLayers.Layer.TiandituLayer("vec_c", "http://localhost:8081/lzugis/tdttile",{
                mapType:"vec_c",
                topLevel: 2,
                bottomLevel: 10,
                isBaseLayer:true,
                isOnline:false
            });
            var cva_c = new OpenLayers.Layer.TiandituLayer("cva_c", "http://t0.tianditu.com/DataServer",{
                mapType:"cva_c",
                topLevel: 0,
                bottomLevel: 18,
                isBaseLayer:false,
                isOnline:true
            });
            map = new OpenLayers.Map({
                div: "map",
                projection: "EPSG:4326",
                layers: [cva_c,vec_c,img_c],
                numZoomLevels:20,
                center: [103.847, 36.0473],
                zoom: 2
            });
            map.addControl(new OpenLayers.Control.LayerSwitcher());
            map.addControl(new OpenLayers.Control.MousePosition());
        }
    </script>
</head>
<body onload="init()">
<div id="map"></div>
</body>
说明:

1、代码中vec_c为天地图矢量层。cva_c为天地图标注层,与天地图的名称相一致;

2、vec_c为离线的地图,cva_c为在线的,通过參数isOnline区分其为离线还是在线。


完毕后效果: