1.引言
由于Arcgis for javascript API不可以绘制Geojson，并且提供的Popup一般只可以弹出一个，在很多专题图制作中，会遇到不少的麻烦。因此本文结合了两个现有的Arcgis for javascript API扩充库，对其进行改造达到绘制Geojson并同时弹出多个Popup的目的。
目前已有的两个扩充库github地址（可供单独使用）：
1.绘制Geojson的扩充库：https://github.com/Esri/geojson-layer-js
2.多个Popup显示的扩充库：https://github.com/nickcam/PopupExtended
本文实现的效果图：
图1 上海5个地点的部分预报属性 图2 上海某三条航线的部分预报属性
2. 各类依赖库引入及前端HTML
首先需要先载入需要用的常用js、Arcgis及两个扩充库的js及部分css（下载地址见其github）：
<!DOCTYPE html>
<html>
<head>
<title>Add GeoJSON and Display Multiple Popup</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=7,IE=9">
<meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no"> <!-- ArcGIS API for JavaScript CSS-->
<link rel="stylesheet" href="http://js.arcgis.com/3.13/esri/css/esri.css">
<link rel="stylesheet" href="http://js.arcgis.com/3.13/dijit/themes/claro/claro.css">
<!-- Web Framework CSS - Bootstrap (getbootstrap.com) and Bootstrap-map-js (github.com/esri/bootstrap-map-js) -->
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css" rel="stylesheet">
<link rel="stylesheet" href="./css/bootstrap.min.css">
<!-- PopExtendCss -->
<link href="./vendor/ncam/PopupExtended.css" rel="stylesheet" /> <!-- PopupExtended references -->
<script>
var dojoConfig = {
parseOnLoad: false,
async: true,
tlmSiblingOfDojo: false,
packages: [{
name: "ncam",
location: location.pathname.replace(/\/[^/]+$/, '') + "ncam"
}]
};
</script> <!-- ArcGIS API for JavaScript library references -->
<script src="//js.arcgis.com/3.10"></script> <!-- Terraformer reference -->
<script src="./vendor/terraformer/terraformer.min.js"></script>
<script src="./vendor/terraformer-arcgis-parser/terraformer-arcgis-parser.min.js"></script> <!-- other reference -->
<script src="./vendor/jquery.js"></script>
</head>
<body> </body>
</html>
加入底图所需要的div与图层切换的Button：
<body>
<div id="mapDiv"></div>
<button type="line" id="shanghaiPoint" class="btn btn-default buttonRight" style="top:20px;right:20px">上海区各点</button>
<button type="point" id="threeLine" class="btn btn-default buttonRight" style="top:70px;right:20px">三条航线</button>
</body>
3.置入Popupextended并扩充geojsonlayer.js
然后从geojsonlayer.js源码入手，开始将PopupExtended扩展其中，让我们新构建的geojsonlayer直接可拥有多个Popup。在geojsonlayer.js的constructor中很容易可以找出infotemplate的set方法：
// Default popup
if (options.infoTemplate !== false) {
this.setInfoTemplate(options.infoTemplate || new InfoTemplate("GeoJSON Data", "${*}"));
}
很明显，geojsonlayer初始化时通过options传入参数进行判断并构造，所以实现本文目的的大致思路是将这里的setInfoTemplate替换成可以扩展的PopupExtended:
if (options.infoTemplate !== false) {
//① create a PopupTemplate
var template = new PopupTemplate({
title: "{name}",
fieldInfos: [
{ fieldName: "Id", label: "Id", visible: true },
{ fieldName: "publishdate", label: "观测日期", visible: true },
{ fieldName: "waveheight", label: "浪高", visible: true },
{ fieldName: "wavedirection", label: "浪向", visible: true },
{ fieldName: "windspeed", label: "风速", visible: true },
{ fieldName: "winddirection", label: "风向", visible: true },
{ fieldName: "comfort", label: "等级", visible: true }
],
extended: {
actions: [
{ text: " IconText", className: "iconText", title: "Custom action with an icon and Text", click: function (feature) { alert("Icon Text clicked on " + "id: " + feature.attributes.id + " " + feature.attributes.name); } },
{ text: "", className: "iconOnly", title: "Custom action only using an icon", click: function (feature) { alert("Icon action clicked on " + "id: " + feature.attributes.id + " " + feature.attributes.name); } }
],
//uses a pretty bad custom theme defined in PopupExtended.css.
scaleSelected: 1.6
}
});
//② create a extend for basemap
var extendedPopup = new PopupExtended({
extended: {
themeClass: "light",
draggable: true,
defaultWidth: 250,
actions: [{
text: "其他", className: "defaultAction", title: "Default action added in extendedPopup properties.",
click: function (feature) { alert("clicked feature - " + feature.attributes); }
}],
hideOnOffClick: false,
multiple: true,
},
highlight: false,
//titleInBody: false,
}, dojo.create("div"));
//③set the map to use the exteneded popup
extendedPopup.setMap(options.baseMap);
options.baseMap.infoWindow = extendedPopup;
this.setInfoTemplate(options.infoTemplate || template);
}
由上段代码可见，引入Popup给GeoJSON共分为三步：①实例化一个你需要的PopupTemplate（这里起名为template），可指定你需要展示的主题、数据项及扩展的一些交互action；②实例化一个PopupExtended并设置一些默认的Popup属性；③将实例化的PopupExtended——extendedPopup的Map设置为baseMap，并将baseMap的infowindow设置为extendedPopup，最后将geojsonlayer的infoTemplate设置为新构建的template。这样便可以实现对置入底图的geojsonlayer进行多个infoTemplate展示需求了。源代码见github:展示效果如图3：
图3 对geojsonlayer扩充Popupextended后的显示效果
如若只需增加多个Popup至geojsonlayer的话，以上部分足以实现了。
4.增加新的Attributes及调整Popup的样式
由于设计上的需求，笔者需要从其他地址获取观测点的部分观测值，并且笔者的老师觉得应该加一些icon给属性，美化展示效果，所以需要重新构造两部分：①获取并为graphics增加新的attributes；②重构geojsonlayer的infoTemplate的content。
4.1 获取并为graphics增加新的attributes：
通过在button上利用fetch及Promise.all来同时获取6个点或3条航线的数据，并传入至初始化geojsonlayer的函数内；
$("#shanghaiPoint").click(function(){
// if first init geojsonlayer
if(firstPointInit){
var requestBZ = 'http://wx.dhybzx.org:18080/forecast/shanghai_sea_env/80';
var requestWGQ = 'http://wx.dhybzx.org:18080/forecast/shanghai_sea_env/81';
var requestHS = 'http://wx.dhybzx.org:18080/forecast/shanghai_sea_env/82';
var requestLCG = 'http://wx.dhybzx.org:18080/forecast/shanghai_sea_env/83';
var requestJHG = 'http://wx.dhybzx.org:18080/forecast/shanghai_sea_env/84';
var requestJSW = 'http://wx.dhybzx.org:18080/forecast/shanghai_sea_env/85';
var urls = [requestBZ, requestWGQ,requestHS,requestLCG,requestJHG,requestJSW]
Promise.all(urls.map(url =>
fetch(url).then(resp => resp.json())
)).then(results => {
var tempJson = {
"堡镇":results[0][0],
"外高桥":results[1][0],
"横沙":results[2][0],
"芦潮港":results[3][0],
"金汇港":results[4][0],
"金山卫":results[5][0]
}
addGeoJsonToMap("./data/six_point.json",tempJson)
});
}else{
//geojsonlayer has been initial
addGeoJsonToMap("./data/six_point.json")
}
})
这里的Promise.all采用了ES2015的箭头函数，兼容性问题需要自己考虑，也可以手动改成ES5支持的。将额外的attributes组装成tempJson后传入至初始化方法addGeoJsonToMap内。
4.2 重构geojsonlayer的infoTemplate的content：
在geojsonlayer.js内继续做一部分修改，注释掉实例化template中的fieldInfos属性及值，并且为geojsonlayer的infoTemplate设置新的content,代码如下：
var template = new PopupTemplate({
title: "{name}",
// fieldInfos: [
// { fieldName: "Id", label: "Id", visible: true },
// { fieldName: "publishdate", label: "观测日期", visible: true },
// { fieldName: "waveheight", label: "浪高", visible: true },
// { fieldName: "wavedirection", label: "浪向", visible: true },
// { fieldName: "windspeed", label: "风速", visible: true },
// { fieldName: "winddirection", label: "风向", visible: true },
// { fieldName: "comfort", label: "等级", visible: true }
// ],
extended: {
actions: [
{ text: " IconText", className: "iconText", title: "Custom action with an icon and Text", click: function (feature) { alert("Icon Text clicked on " + "id: " + feature.attributes.id + " " + feature.attributes.name); } },
{ text: "", className: "iconOnly", title: "Custom action only using an icon", click: function (feature) { alert("Icon action clicked on " + "id: " + feature.attributes.id + " " + feature.attributes.name); } }
],
//uses a pretty bad custom theme defined in PopupExtended.css.
scaleSelected: 1.6
}
});
//create a extend for basemap
var extendedPopup = new PopupExtended({
extended: {
themeClass: "light",
draggable: true,
defaultWidth: 250,
actions: [{
text: "其他", className: "defaultAction", title: "Default action added in extendedPopup properties.",
click: function (feature) { alert("clicked feature - " + feature.attributes); }
}],
hideOnOffClick: false,
multiple: true,
},
highlight: false,
//titleInBody: false,
}, dojo.create("div"));
//set the map to use the exteneded popup
extendedPopup.setMap(options.baseMap);
options.baseMap.infoWindow = extendedPopup;
this.setInfoTemplate(options.infoTemplate || template);
this.infoTemplate.setContent("<b class='popupTitle'>${name}</b>" +
"<div class='hzLine'></div>"+
"<div class='popupContent'>"+
"<i class='glyphicon glyphicon-calendar'></i><b>日期: </b> ${publishdate}<br/>"+
"<i class='glyphicon glyphicon-resize-vertical'></i><b>浪高: </b> ${waveheight}<br/>" +
"<i class='glyphicon glyphicon-random'></i><b>浪向: </b> ${wavedirection}<br/>"+
"<i class='glyphicon glyphicon-share'></i><b>风速: </b> ${windspeed}<br/>" +
"<i class='glyphicon glyphicon-transfer'></i><b>风向: </b> ${winddirection}<br/>"+
"<i class='glyphicon glyphicon-export'></i><b>等级: </b> ${comfort}<br/>"+
"</div>"
);
额外的属性和新的infoTemplate样式构造完成，但存在一个问题，即额外的attributes必须要在geojsonlayer绘制好后再进行设置并展示，arcgis提供了layer的layer-add及layer-add-result事件，但是无法监控到graphics是否已经增入至geojsonlayer内，所以必须要再做一些改进，使额外的属性能够在graphics绘制完毕后再添加进去。具体方法分为两步：1）初始化geojsonlayer时，将showAllPopup方法传入其构造函数内；2）在grahics添加至layer后，调用showAllPopup方法，显示所有的Popup。前端代码如下：
//add GeoJSON to baseMap , constuct show&hide popup method and add other attribute to graphics
function addGeoJsonToMap(url,otherJson){ require(["esri/map",
"./src/geojsonlayer.js",
"esri/geometry/Point", "esri/SpatialReference",
"dojo/on",
"dojo/dom",
"dojo/domReady!"],
function (Map, GeoJsonLayer, Point, SpatialReference,on, dom) { var hasThisLayer=false;
otherJson=otherJson?otherJson:"";
hideAllPopup()
//judge layer has been init
map.getLayersVisibleAtScale().forEach(function(item){
if(item._url==url&&item.dataType=="geojson"){
console.log(item)
item.show();
console.log("dd")
showAllPopup(item);
hasThisLayer=true;
// map.setExtent(item.extent)
}else if(item._url!=url&&item.dataType=="geojson"){
item.hide();
}
}) if(!hasThisLayer){
addGeoJsonLayer(url);
} //show all popups
function showAllPopup(layer){
......
} //hide all popups
function hideAllPopup(){
.......
} //add other attribute to grpahics for popup
function addAttrToGrpahics(item,type){
.......
} // Add the layer
function addGeoJsonLayer(url) {
// Create the layer
var geoJsonLayer = new GeoJsonLayer({
baseMap:map,
url: url,
onLayerLoaded:function(layer){
showAllPopup(layer);
}
}); // Add to map
geoJsonLayer.dataType="geojson";
map.addLayer(geoJsonLayer); }
});
}
并且在geojsonlayer.js的constructor内加入：
this._onLayerLoaded = options.onLayerLoaded;
在最后的_addGraphics方法中onLoad方法后，加入：
if (this._onLayerLoaded) this._onLayerLoaded(this);
利用show/hide方法，控制popup显示及隐藏。
//open all popup
layer.graphics.forEach(function(item){
if(firstPointInit&&otherJson[item.attributes.name]){
addAttrToGrpahics(item,layer.graphics[0].geometry.type)
}
var loc = map.toScreen(item.geometry);
map.infoWindow.setFeatures([item]);
map.infoWindow.show(loc);
})
//hide all popup
var tempLength = map.infoWindow.openPopups.length;
for(var i=0;i<tempLength;i++){
map.infoWindow.openPopups[0].hide()
}
5. 结论
至此，本文已经完成了在Arcgis for javascript API中实现Geojson的绘制，并同时展示其多个Popup的需求。最终的展示效果如图1、2。源代码见笔者的github:https://github.com/EasonXu818/Add-GeoJSON-Multiple-Popups。