GIS开发记录(七)：基于Scale切换地图BaseLayer
程序员文章站
2022-04-17 20:13:54
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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&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：