在Arcgis api for javascript 3.x 版本中，我们可以直接通过某个FeatureLayer对象中的graphics属性获取要素集合。 graphics属性
但是在4.x版本中，FeatureLayer对象并未提供graphics属性。所以我们要获取必须通过某些query的函数来实现。
方法一： 通过FeatureLayer中的queryFeatures()函数。 queryFeatures()函数
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
<title>FeatureLayer - 4.7</title>
<style>
html, body, #viewDiv {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
}
</style>
<link rel="stylesheet" href="https://js.arcgis.com/4.7/esri/css/main.css">
<script src="https://js.arcgis.com/4.7/"></script>
</head>
<body>
<div id="viewDiv"></div>
<script type="text/javascript">
require([
"esri/Map",
"esri/views/MapView",
"esri/layers/FeatureLayer",
"dojo/domReady!"
],
function (Map, MapView, FeatureLayer) {
let map = new Map({
basemap: "hybrid"
}); let view = new MapView({
container: "viewDiv",
map: map,
extent: { // autocasts as new Extent()
xmin: -9177811,
ymin: 4247000,
xmax: -9176791,
ymax: 4247784,
spatialReference: 102100
}
}); let featureLayer = new FeatureLayer({
url: "https://services.arcgis.com/V6ZHFr6zdgNZuVG0/arcgis/rest/services/Landscape_Trees/FeatureServer/0"
});
map.add(featureLayer); view.when(function () {
featureLayer.queryFeatures().then(function (results) {
console.log(results.features);
});
});
});
</script>
</body>
</html>
这种方式有一个缺点就是，需要再一次向服务器发送一条查询的请求，其实照理说完全可以在已有的FeatureLayer对象中获取它的要素集合。
方法二：通过FeatureLayerView中的queryFeatures()函数来实现，它不会再一次向服务器发送请求。 FeatureLayerView中的queryFeatures()函数
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
<title>FeatureLayer - 4.7</title>
<style>
html, body, #viewDiv {
padding: 0;
margin: 0;
height: 100%;
width: 100%;
}
</style>
<link rel="stylesheet" href="https://js.arcgis.com/4.7/esri/css/main.css">
<script src="https://js.arcgis.com/4.7/"></script>
</head>
<body>
<div id="viewDiv"></div>
<script type="text/javascript">
require([
"esri/Map",
"esri/views/MapView",
"esri/layers/FeatureLayer",
"dojo/domReady!"
],
function (Map, MapView, FeatureLayer) {
let map = new Map({
basemap: "hybrid"
}); let view = new MapView({
container: "viewDiv",
map: map,
extent: { // autocasts as new Extent()
xmin: -9177811,
ymin: 4247000,
xmax: -9176791,
ymax: 4247784,
spatialReference: 102100
}
}); let featureLayer1 = new FeatureLayer({
url: "https://services.arcgis.com/V6ZHFr6zdgNZuVG0/arcgis/rest/services/Landscape_Trees/FeatureServer/0"
});
map.add(featureLayer1); view.when(function () {
//地图刚初始化时获取graphics集合，需要监控featureLayer的updating状态完成后才能获取到
view.whenLayerView(featureLayer1).then(function (lyrView) {
lyrView.watch("updating", function(){
lyrView.queryFeatures().then(function (results) {
console.log(results);
});
});
}); //地图加载完成后，可以随时获取featureLayer中的graphics集合
view.on("double-click",function () {
view.whenLayerView(featureLayer1).then(function (lyrView) {
lyrView.queryFeatures().then(function (results) {
console.log(results);
});
});
});
});
}
);
</script>
</body>
</html>