QueryTask简化版
文章目录
前言一、QueryTask、FindTask、IdentifyTask之间的区别二、QueryTask使用步骤1.创建QueryTask对象2.创建Query并设置参数3.执行查询4.渲染查询结果
三、全部代码总结
前言
QueryTask用于查询，可以进行属性查询和空间查询，但是只能查询一个图层的数据。与之搭配使用的是Query，用于设置查询的参数。
一、QueryTask、FindTask、IdentifyTask之间的区别
FindTask：只能进行属性查询，可以查询多个图层，不能进行精确查询，其中的searchText参数进行的like查询。 QueryTask：只能查询一个图层，可以进行属性查询、空间查询，可以进行设置where条件，也可以使用text的简化版like查询 IdentifyTask：可以进行属性查询和空间查询，可以查询多个图层。
二、QueryTask使用步骤
1.创建QueryTask对象
代码如下（示例）：
var queryTask
= new QueryTask("https://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5");
2.创建Query并设置参数
代码如下（示例）：
var query
= new Query();
query
.returnGeometry
= false;
query
.outFields
= [
"SQMI", "STATE_NAME", "STATE_FIPS", "SUB_REGION", "STATE_ABBR",
"POP2000", "POP2007", "POP00_SQMI", "POP07_SQMI", "HOUSEHOLDS",
"MALES", "FEMALES", "WHITE", "BLACK", "AMERI_ES", "ASIAN", "OTHER",
"HISPANIC", "AGE_UNDER5", "AGE_5_17", "AGE_18_21", "AGE_22_29",
"AGE_30_39", "AGE_40_49", "AGE_50_64", "AGE_65_UP"
];
3.执行查询
on(dom
.byId("execute"), "click", execute
);
function execute () {
query
.text
= dom
.byId("stateName").value
;
queryTask
.execute(query
, showResults
);
}
4.渲染查询结果
function showResults (results
) {
var resultItems
= [];
var resultCount
= results
.features
.length
;
for (var i
= 0; i
< resultCount
; i
++) {
var featureAttributes
= results
.features
[i
].attributes
;
for (var attr
in featureAttributes
) {
resultItems
.push("<b>" + attr
+ ":</b> " + featureAttributes
[attr
] + "<br>");
}
}
dom
.byId("info").innerHTML
= resultItems
.join("");
}
该处使用的url网络请求的数据。
三、全部代码
<!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>Query State Info without Map
</title>
<script src="https://js.arcgis.com/3.34/"></script>
<script>
require([
"dojo/dom", "dojo/on",
"esri/tasks/query", "esri/tasks/QueryTask", "dojo/domReady!"
], function (dom, on, Query, QueryTask) {
var queryTask = new QueryTask("https://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer/5");
var query = new Query();
query.returnGeometry = false;
query.outFields = [
"SQMI", "STATE_NAME", "STATE_FIPS", "SUB_REGION", "STATE_ABBR",
"POP2000", "POP2007", "POP00_SQMI", "POP07_SQMI", "HOUSEHOLDS",
"MALES", "FEMALES", "WHITE", "BLACK", "AMERI_ES", "ASIAN", "OTHER",
"HISPANIC", "AGE_UNDER5", "AGE_5_17", "AGE_18_21", "AGE_22_29",
"AGE_30_39", "AGE_40_49", "AGE_50_64", "AGE_65_UP"
];
on(dom.byId("execute"), "click", execute);
function execute () {
query.text = dom.byId("stateName").value;
queryTask.execute(query, showResults);
}
function showResults (results) {
var resultItems = [];
var resultCount = results.features.length;
for (var i = 0; i < resultCount; i++) {
var featureAttributes = results.features[i].attributes;
for (var attr in featureAttributes) {
resultItems.push("<b>" + attr + ":</b> " + featureAttributes[attr] + "<br>");
}
}
dom.byId("info").innerHTML = resultItems.join("");
}
});
</script>
</head>
<body>
US state name :
<input type="text" id="stateName" value="California">
<input id="execute" type="button" value="Get Details">
<br />
<br />
<div id="info" style="padding:5px; margin:5px; background-color:#eee;">
</div>
</body>
</html>
代码来源：esri demo
总结
QueryTask可以实现查询属性，这里本人在学习这里的时候想到了一个问题，如何像前面的FeatureTable一样显示的属性点击就能缩放到地图？希望有大佬解惑。
