出自點擊打開鏈接
當我們將一個圖層發佈爲服務後，在JS代碼中想取到圖層裏面的數據該怎麼做呢？在下面的例子中將演示當鼠標點擊圖層點時彈出圖層屬性的過程。
一、測試數據 
二、發佈服務
三、引用服務
引用服務的代碼如下：
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no">
<title>Create Map and add a dynamic layer</title>
<!--使用的是本機離線API-->
<link rel="stylesheet" type="text/css" href="http://localhost/arcgis_js_api/library/3.18/3.18/dijit/themes/claro/claro.css"/>
<link rel="stylesheet" type="text/css" href="http://localhost/arcgis_js_api/library/3.18/3.18/esri/css/esri.css" />
<script src="http://localhost/arcgis_js_api/library/3.18/3.18/init.js" djConfig="parseOnLoad:true"></script>
<style>
html, body, #map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
}
</style>
<script>
require([
"esri/map",
"esri/layers/FeatureLayer",
"esri/layers/LabelClass",
"dojo/_base/Color",
"esri/symbols/Font",
"esri/symbols/TextSymbol",
"dojo/domReady!"
],
function(
Map,
FeatureLayer,
LabelClass,Color,Font,TextSymbol
) {
var map = new Map("map",{
showLabels : true
});
/****************************************************************
* Add feature layer - A FeatureLayer at minimum should point
* to a URL to a feature service or point to a feature collection
* object.
***************************************************************/
// Carbon storage of trees in Warren Wilson College.
var featureLayer = new FeatureLayer("http://localhost:6080/arcgis/rest/services/cs/MapServer/0",{
mode: FeatureLayer.MODE_SNAPSHOT,
outFields: ["*"] //顯示所有字段
});
//地名標註
var labelSymbol = new TextSymbol().setColor(new Color("#000000"));
labelSymbol.font.setSize("10pt");
labelSymbol.font.setFamily("新宋體");
var json = {
"labelExpressionInfo": {"value": "{Point}"},
"useCodedValues": false,
"labelPlacement":"center-right"
};
var labelClass = new LabelClass(json);
labelClass.symbol = labelSymbol;
featureLayer.setLabelingInfo([ labelClass ]);
map.addLayer(featureLayer);
});
</script>
</head>
<body>
<div id="map"></div>
</body>
</html>
運行結果：
四、輸出圖層屬性的值
1、輸出featureLayer
首先看看添加的featureLayer輸出的是什麼？
...
map.addLayer(featureLayer);
console.log(featureLayer);
...
其中重點是graphics
graphics是一個數組，展開graphics可以看到有5個變量，對應5個點的數據。
隨便展開一個，可以看到圖層的屬性數據就包含在attributes中。
2、輸出graphics
在前面我們看到圖層的數據就存在graphics中，那把graphics輸出會得到什麼呢？
...
map.addLayer(featureLayer);
//輸出graphics
console.log(featureLayer.graphics);
...
結果卻顯示graphics的長度爲0，裏面沒有數據。
這是因爲layer還沒有添加到map中，所以拿不到屬性數據。
3、添加“update-end”事件
...
map.addLayer(featureLayer);
//添加“update-end”事件
map.on("update-end", function(){
// update-end event will execute after the layer has been added to the map
if(featureLayer.graphics.length >= 1)
{
// do your thing
console.log(featureLayer.graphics);
}
});
...
4、輸出attributes
...
//輸出第一條記錄的Point變量和NUM變量
var point=featureLayer.graphics[0].attributes.Point;
var num=featureLayer.graphics[0].attributes.NUM;
console.log("Point:"+point+" NUM:"+num);
...
三、完整代碼
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no">
<title>Create Map and add a dynamic layer</title>
<link rel="stylesheet" type="text/css" href="http://localhost/arcgis_js_api/library/3.18/3.18/dijit/themes/claro/claro.css"/>
<link rel="stylesheet" type="text/css" href="http://localhost/arcgis_js_api/library/3.18/3.18/esri/css/esri.css" />
<script src="http://localhost/arcgis_js_api/library/3.18/3.18/init.js" djConfig="parseOnLoad:true"></script>
<style>
html, body, #map {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
}
</style>
<script>
require([
"esri/map",
"esri/layers/FeatureLayer",
"esri/layers/LabelClass",
"dojo/_base/Color",
"esri/symbols/Font",
"esri/symbols/TextSymbol",
"dojo/domReady!"
],
function(
Map,
FeatureLayer,
LabelClass,Color,Font,TextSymbol
) {
var map = new Map("map",{
showLabels : true
});
/****************************************************************
* Add feature layer - A FeatureLayer at minimum should point
* to a URL to a feature service or point to a feature collection
* object.
***************************************************************/
// Carbon storage of trees in Warren Wilson College.
var featureLayer = new FeatureLayer("http://localhost:6080/arcgis/rest/services/cs/MapServer/0",{
mode: FeatureLayer.MODE_SNAPSHOT,
outFields: ["*"]
});
//地名標註
var labelSymbol = new TextSymbol().setColor(new Color("#000000"));
labelSymbol.font.setSize("10pt");
labelSymbol.font.setFamily("新宋體");
var json = {
"labelExpressionInfo": {"value": "{Point}"},
"useCodedValues": false,
"labelPlacement":"center-right"
};
var labelClass = new LabelClass(json);
labelClass.symbol = labelSymbol;
featureLayer.setLabelingInfo([ labelClass ]);
map.addLayer(featureLayer);
//添加“update-end”事件
map.on("update-end", function(){
// update-end event will execute after the layer has been added to the map
if(featureLayer.graphics.length >= 1)
{
// do your thing
console.log(featureLayer.graphics);
var point=featureLayer.graphics[0].attributes.Point;
var num=featureLayer.graphics[0].attributes.NUM;
console.log("Point:"+point+" NUM:"+num);
}
});
});
</script>
</head>
<body>
<div id="map"></div>
</body>
</html>