在做項目的時候，碰見了這樣一個問題：給地圖上標註點對象，數據是從數據庫來的，包含XY座標信息的，通過graphic和graphiclayer 的方式添加到地圖上，其中有一個對象的數量很多，上萬了吧，通過上述的方式無法在地圖上進行展示，就想到了聚類，當時由於技術和時間的關係，沒有實現，最近，稍微有點先下時間，就又想起這事，繼續研究，終於，皇天不負有心人，出來了，出來的第一時間寫出來，以便大家使用。
首先，看看實現後的效果：
初始化狀態
點擊對象顯示詳細對象和信息框
放大後的效果
效果就是上面所示的這個樣子的，下面說說實現的步驟與思路：
1、數據
正常數據的來源是源自數據庫的JSON數據，在本例子中，新建了一個變量用來模擬JSON數據，我所用的數據是全國的市縣級的點狀數據轉換來的，如下：
2、clusterLayer的封裝
根據需求，對GraphicsLayer進行了封裝爲clusterLayer，來源爲Arcgis for JS官方實例，對其中個別代碼做了修改，源代碼如下：
define([
"dojo/_base/declare",
"dojo/_base/array",
"esri/Color",
"dojo/_base/connect",
"esri/SpatialReference",
"esri/geometry/Point",
"esri/graphic",
"esri/symbols/SimpleMarkerSymbol",
"esri/symbols/TextSymbol",
"esri/dijit/PopupTemplate",
"esri/layers/GraphicsLayer"
], function (
declare, arrayUtils, Color, connect,
SpatialReference, Point, Graphic, SimpleMarkerSymbol, TextSymbol,
PopupTemplate, GraphicsLayer
) {
return declare([GraphicsLayer], {
constructor: function(options) {
// options:
// data: Object[]
// Array of objects. Required. Object are required to have properties named x, y and attributes. The x and y coordinates have to be numbers that represent a points coordinates.
// distance: Number?
// Optional. The max number of pixels between points to group points in the same cluster. Default value is 50.
// labelColor: String?
// Optional. Hex string or array of rgba values used as the color for cluster labels. Default value is #fff (white).
// labelOffset: String?
// Optional. Number of pixels to shift a cluster label vertically. Defaults to -5 to align labels with circle symbols. Does not work in IE.
// resolution: Number
// Required. Width of a pixel in map coordinates. Example of how to calculate:
// map.extent.getWidth() / map.width
// showSingles: Boolean?
// Optional. Whether or graphics should be displayed when a cluster graphic is clicked. Default is true.
// singleSymbol: MarkerSymbol?
// Marker Symbol (picture or simple). Optional. Symbol to use for graphics that represent single points. Default is a small gray SimpleMarkerSymbol.
// singleTemplate: PopupTemplate?
// PopupTemplate</a>. Optional. Popup template used to format attributes for graphics that represent single points. Default shows all attributes as "attribute = value" (not recommended).
// maxSingles: Number?
// Optional. Threshold for whether or not to show graphics for points in a cluster. Default is 1000.
// webmap: Boolean?
// Optional. Whether or not the map is from an ArcGIS.com webmap. Default is false.
// spatialReference: SpatialReference?
// Optional. Spatial reference for all graphics in the layer. This has to match the spatial reference of the map. Default is 102100. Omit this if the map uses basemaps in web mercator.
this._clusterTolerance = options.distance || 50;
this._clusterData = options.data || [];
this._clusters = [];
this._clusterLabelColor = options.labelColor || "#000";
// labelOffset can be zero so handle it differently
this._clusterLabelOffset = (options.hasOwnProperty("labelOffset")) ? options.labelOffset : -5;
// graphics that represent a single point
this._singles = []; // populated when a graphic is clicked
this._showSingles = options.hasOwnProperty("showSingles") ? options.showSingles : true;
// symbol for single graphics
var SMS = SimpleMarkerSymbol;
this._singleSym = options.singleSymbol || new SMS("circle", 6, null, new Color(options.singleColor));
this._singleTemplate = options.singleTemplate || new PopupTemplate({ "title": "", "description": "{*}" });
this._maxSingles = options.maxSingles || 1000;
this._webmap = options.hasOwnProperty("webmap") ? options.webmap : false;
this._sr = options.spatialReference || new SpatialReference({ "wkid": 102100 });
this._zoomEnd = null;
},
// override esri/layers/GraphicsLayer methods
_setMap: function(map, surface) {
// calculate and set the initial resolution
this._clusterResolution = map.extent.getWidth() / map.width; // probably a bad default...
this._clusterGraphics();
// connect to onZoomEnd so data is re-clustered when zoom level changes
this._zoomEnd = connect.connect(map, "onZoomEnd", this, function() {
// update resolution
this._clusterResolution = this._map.extent.getWidth() / this._map.width;
this.clear();
this._clusterGraphics();
});
// GraphicsLayer will add its own listener here
var div = this.inherited(arguments);
return div;
},
_unsetMap: function() {
this.inherited(arguments);
connect.disconnect(this._zoomEnd);
},
// public ClusterLayer methods
add: function(p) {
// Summary: The argument is a data point to be added to an existing cluster. If the data point falls within an existing cluster, it is added to that cluster and the cluster's label is updated. If the new point does not fall within an existing cluster, a new cluster is created.
//
// if passed a graphic, use the GraphicsLayer's add method
if ( p.declaredClass ) {
this.inherited(arguments);
return;
}
// add the new data to _clusterData so that it's included in clusters
// when the map level changes
this._clusterData.push(p);
var clustered = false;
// look for an existing cluster for the new point
for ( var i = 0; i < this._clusters.length; i++ ) {
var c = this._clusters[i];
if ( this._clusterTest(p, c) ) {
// add the point to an existing cluster
this._clusterAddPoint(p, c);
// update the cluster's geometry
this._updateClusterGeometry(c);
// update the label
this._updateLabel(c);
clustered = true;
break;
}
}
if ( ! clustered ) {
this._clusterCreate(p);
p.attributes.clusterCount = 1;
this._showCluster(p);
}
},
clear: function() {
// Summary: Remove all clusters and data points.
this.inherited(arguments);
this._clusters.length = 0;
},
clearSingles: function(singles) {
// Summary: Remove graphics that represent individual data points.
var s = singles || this._singles;
arrayUtils.forEach(s, function(g) {
this.remove(g);
}, this);
this._singles.length = 0;
},
onClick: function(e) {
// remove any previously showing single features
this.clearSingles(this._singles);
// find single graphics that make up the cluster that was clicked
// would be nice to use filter but performance tanks with large arrays in IE
var singles = [];
for ( var i = 0, il = this._clusterData.length; i < il; i++) {
if ( e.graphic.attributes.clusterId == this._clusterData[i].attributes.clusterId ) {
singles.push(this._clusterData[i]);
}
}
if ( singles.length > this._maxSingles ) {
alert("Sorry, that cluster contains more than " + this._maxSingles + " points. Zoom in for more detail.");
return;
} else {
// stop the click from bubbling to the map
e.stopPropagation();
this._map.infoWindow.show(e.graphic.geometry);
this._addSingles(singles);
}
},
// internal methods
_clusterGraphics: function() {
// first time through, loop through the points
for ( var j = 0, jl = this._clusterData.length; j < jl; j++ ) {
// see if the current feature should be added to a cluster
var point = this._clusterData[j];
var clustered = false;
var numClusters = this._clusters.length;
for ( var i = 0; i < this._clusters.length; i++ ) {
var c = this._clusters[i];
if ( this._clusterTest(point, c) ) {
this._clusterAddPoint(point, c);
clustered = true;
break;
}
}
if ( ! clustered ) {
this._clusterCreate(point);
}
}
this._showAllClusters();
},
_clusterTest: function(p, cluster) {
var distance = (
Math.sqrt(
Math.pow((cluster.x - p.x), 2) + Math.pow((cluster.y - p.y), 2)
) / this._clusterResolution
);
return (distance <= this._clusterTolerance);
},
// points passed to clusterAddPoint should be included
// in an existing cluster
// also give the point an attribute called clusterId
// that corresponds to its cluster
_clusterAddPoint: function(p, cluster) {
// average in the new point to the cluster geometry
var count, x, y;
count = cluster.attributes.clusterCount;
x = (p.x + (cluster.x * count)) / (count + 1);
y = (p.y + (cluster.y * count)) / (count + 1);
cluster.x = x;
cluster.y = y;
// build an extent that includes all points in a cluster
// extents are for debug/testing only...not used by the layer
if ( p.x < cluster.attributes.extent[0] ) {
cluster.attributes.extent[0] = p.x;
} else if ( p.x > cluster.attributes.extent[2] ) {
cluster.attributes.extent[2] = p.x;
}
if ( p.y < cluster.attributes.extent[1] ) {
cluster.attributes.extent[1] = p.y;
} else if ( p.y > cluster.attributes.extent[3] ) {
cluster.attributes.extent[3] = p.y;
}
// increment the count
cluster.attributes.clusterCount++;
// attributes might not exist
if ( ! p.hasOwnProperty("attributes") ) {
p.attributes = {};
}
// give the graphic a cluster id
p.attributes.clusterId = cluster.attributes.clusterId;
},
// point passed to clusterCreate isn't within the
// clustering distance specified for the layer so
// create a new cluster for it
_clusterCreate: function(p) {
var clusterId = this._clusters.length + 1;
// console.log("cluster create, id is: ", clusterId);
// p.attributes might be undefined
if ( ! p.attributes ) {
p.attributes = {};
}
p.attributes.clusterId = clusterId;
// create the cluster
var cluster = {
"x": p.x,
"y": p.y,
"attributes" : {
"clusterCount": 1,
"clusterId": clusterId,
"extent": [ p.x, p.y, p.x, p.y ]
}
};
this._clusters.push(cluster);
},
_showAllClusters: function() {
for ( var i = 0, il = this._clusters.length; i < il; i++ ) {
var c = this._clusters[i];
this._showCluster(c);
}
},
_showCluster: function(c) {
var point = new Point(c.x, c.y, this._sr);
this.add(
new Graphic(
point,
null,
c.attributes
)
);
// code below is used to not label clusters with a single point
if ( c.attributes.clusterCount == 1 ) {
return;
}
// show number of points in the cluster
var font = new esri.symbol.Font()
.setSize("10pt")
.setWeight(esri.symbol.Font.WEIGHT_BOLD);
var label = new TextSymbol(c.attributes.clusterCount)
.setColor(new Color(this._clusterLabelColor))
.setOffset(0, this._clusterLabelOffset)
.setFont(font);
this.add(
new Graphic(
point,
label,
c.attributes
)
);
},
_addSingles: function(singles) {
// add single graphics to the map
arrayUtils.forEach(singles, function(p) {
var g = new Graphic(
new Point(p.x, p.y, this._sr),
this._singleSym,
p.attributes,
this._singleTemplate
);
this._singles.push(g);
if ( this._showSingles ) {
this.add(g);
}
}, this);
this._map.infoWindow.setFeatures(this._singles);
},
_updateClusterGeometry: function(c) {
// find the cluster graphic
var cg = arrayUtils.filter(this.graphics, function(g) {
return ! g.symbol &&
g.attributes.clusterId == c.attributes.clusterId;
});
if ( cg.length == 1 ) {
cg[0].geometry.update(c.x, c.y);
} else {
console.log("didn't find exactly one cluster geometry to update: ", cg);
}
},
_updateLabel: function(c) {
// find the existing label
var label = arrayUtils.filter(this.graphics, function(g) {
return g.symbol &&
g.symbol.declaredClass == "esri.symbol.TextSymbol" &&
g.attributes.clusterId == c.attributes.clusterId;
});
if ( label.length == 1 ) {
// console.log("update label...found: ", label);
this.remove(label[0]);
var newLabel = new TextSymbol(c.attributes.clusterCount)
.setColor(new Color(this._clusterLabelColor))
.setOffset(0, this._clusterLabelOffset);
this.add(
new Graphic(
new Point(c.x, c.y, this._sr),
newLabel,
c.attributes
)
);
// console.log("updated the label");
} else {
console.log("didn't find exactly one label: ", label);
}
},
// debug only...never called by the layer
_clusterMeta: function() {
// print total number of features
console.log("Total: ", this._clusterData.length);
// add up counts and print it
var count = 0;
arrayUtils.forEach(this._clusters, function(c) {
count += c.attributes.clusterCount;
});
console.log("In clusters: ", count);
}
});
});3、ClusterLayer的導入與引用
文件目錄
如上圖所示文件目錄，dojo導入的方式爲：
<script>
// helpful for understanding dojoConfig.packages vs. dojoConfig.paths:
// http://www.sitepen.com/blog/2013/06/20/dojo-faq-what-is-the-difference-packages-vs-paths-vs-aliases/
var dojoConfig = {
paths: {
extras: location.pathname.replace(/\/[^/]+$/, "") + "/extras"
}
};
</script>在代碼中引用的代碼爲：
require([
"extras/ClusterLayer"
], function(
ClusterLayer
){
});4、地圖、圖層的加載等
完成上述操作，就能去實現聚類了，代碼如下：
parser.parse();
map = new Map("map", {logo:false,slider: true});
var tiled = new Tiled("http://localhost:6080/arcgis/rest/services/image/MapServer");
map.addLayer(tiled,0);
map.centerAndZoom(new Point(103.847, 36.0473, map.spatialReference),4);
map.on("load", function() {
addClusters(county.items);
});
function addClusters(items) {
console.log(items);
var countyInfo = {};
countyInfo.data = arrayUtils.map(items, function(item) {
var latlng = new Point(parseFloat(item.x), parseFloat(item.y), map.spatialReference);
var webMercator = webMercatorUtils.geographicToWebMercator(latlng);
var attributes = {
"名稱": item.name,
"經度": item.x,
"緯度": item.y
};
return {
"x": webMercator.x,
"y": webMercator.y,
"attributes": attributes
};
});
console.log(countyInfo.data);
// cluster layer that uses OpenLayers style clustering
clusterLayer = new ClusterLayer({
"data": countyInfo.data,
"distance": 150,
"id": "clusters",
"labelColor": "#fff",
"labelOffset": -4,
"resolution": map.extent.getWidth() / map.width,
"singleColor": "#f00",
"maxSingles":3000
});
var defaultSym = new SimpleMarkerSymbol().setSize(4);
var renderer = new ClassBreaksRenderer(defaultSym, "clusterCount");
/*var picBaseUrl = "images/";
var blue = new PictureMarkerSymbol(picBaseUrl + "BluePin1LargeB.png", 32, 32).setOffset(0, 15);
var green = new PictureMarkerSymbol(picBaseUrl + "GreenPin1LargeB.png", 64, 64).setOffset(0, 15);
var red = new PictureMarkerSymbol(picBaseUrl + "RedPin1LargeB.png", 80, 80).setOffset(0, 15);*/
var style1 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 10,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([255,200,0]), 1),
new Color([255,200,0,0.8]));
var style2 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 25,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([255,125,3]), 1),
new Color([255,125,3,0.8]));
var style3 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 30,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([255,23,58]), 1),
new Color([255,23,58,0.8]));
var style4 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 35,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([204,0,184]), 1),
new Color([204,0,184,0.8]));
var style5 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 40,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([0,0,255]), 1),
new Color([0,0,255,0.8]));
renderer.addBreak(0, 2, style1);
renderer.addBreak(2, 100, style2);
renderer.addBreak(100, 500, style3);
renderer.addBreak(500, 1000, style4);
renderer.addBreak(1000, 3001, style5);
clusterLayer.setRenderer(renderer);
map.addLayer(clusterLayer);
// close the info window when the map is clicked
map.on("click", cleanUp);
// close the info window when esc is pressed
map.on("key-down", function(e) {
if (e.keyCode === 27) {
cleanUp();
}
});
}
function cleanUp() {
map.infoWindow.hide();
clusterLayer.clearSingles();
}注：在創建ClusterLayer對象時有以下幾個參數，
1、distance
distance控制的是兩個點之間的距離，distance值越小，點密度越大，反之亦然；
2、labelColor
labelColor爲個數顯示的顏色；
3、labelOffset
labelOffset默認值爲0，+爲向上，-爲向下；
4、singleColor
singleColor爲單個對象出現時顯示的顏色；
5、maxSingles
maxSingles是最多可顯示多少個點。
6、resolution
resolution是一個變化的值，當前的地圖範圍/地圖的範圍即爲resolution；
7、對ClusterLayer進行ClassBreaksRenderer
此處ClassBreaksRenderer的短點的值可按照數據的多少來確定。
cluster.html的源碼如下：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1, maximum-scale=1,user-scalable=no">
<title>Cluster</title>
<link rel="stylesheet" href="http://localhost/arcgis_js_api/library/3.9/3.9/js/dojo/dijit/themes/tundra/tundra.css">
<link rel="stylesheet" href="http://localhost/arcgis_js_api/library/3.9/3.9/js/esri/css/esri.css">
<style>
html, body, #map{ height: 100%; width: 100%; margin: 0; padding: 0; }
#map{ margin: 0; padding: 0; }
</style>
<script>
// helpful for understanding dojoConfig.packages vs. dojoConfig.paths:
// http://www.sitepen.com/blog/2013/06/20/dojo-faq-what-is-the-difference-packages-vs-paths-vs-aliases/
var dojoConfig = {
paths: {
extras: location.pathname.replace(/\/[^/]+$/, "") + "/extras"
}
};
</script>
<script src="http://localhost/arcgis_js_api/library/3.9/3.9/init.js"></script>
<script src="data/county.js"></script>
<script>
var map;
var clusterLayer;
require([
"dojo/parser",
"dojo/_base/array",
"esri/Color",
"esri/map",
"esri/layers/ArcGISTiledMapServiceLayer",
"esri/request",
"esri/graphic",
"esri/geometry/Extent",
"esri/symbols/SimpleMarkerSymbol",
"esri/symbols/PictureMarkerSymbol",
"esri/symbols/SimpleLineSymbol",
"esri/symbols/SimpleFillSymbol",
"esri/renderers/ClassBreaksRenderer",
"esri/layers/GraphicsLayer",
"esri/SpatialReference",
"esri/geometry/Point",
"esri/geometry/webMercatorUtils",
"extras/ClusterLayer",
"dojo/domReady!"
], function(
parser,
arrayUtils,
Color,
Map,
Tiled,
esriRequest,
Graphic,
Extent,
SimpleMarkerSymbol,
PictureMarkerSymbol,
SimpleLineSymbol,
SimpleFillSymbol,
ClassBreaksRenderer,
GraphicsLayer,
SpatialReference,
Point,
webMercatorUtils,
ClusterLayer
){
parser.parse();
map = new Map("map", {logo:false,slider: true});
var tiled = new Tiled("http://localhost:6080/arcgis/rest/services/image/MapServer");
map.addLayer(tiled,0);
map.centerAndZoom(new Point(103.847, 36.0473, map.spatialReference),4);
map.on("load", function() {
addClusters(county.items);
});
function addClusters(items) {
console.log(items);
var countyInfo = {};
countyInfo.data = arrayUtils.map(items, function(item) {
var latlng = new Point(parseFloat(item.x), parseFloat(item.y), map.spatialReference);
var webMercator = webMercatorUtils.geographicToWebMercator(latlng);
var attributes = {
"名稱": item.name,
"經度": item.x,
"緯度": item.y
};
return {
"x": webMercator.x,
"y": webMercator.y,
"attributes": attributes
};
});
console.log(countyInfo.data);
// cluster layer that uses OpenLayers style clustering
clusterLayer = new ClusterLayer({
"data": countyInfo.data,
"distance": 150,
"id": "clusters",
"labelColor": "#fff",
"labelOffset": -4,
"resolution": map.extent.getWidth() / map.width,
"singleColor": "#f00",
"maxSingles":3000
});
var defaultSym = new SimpleMarkerSymbol().setSize(4);
var renderer = new ClassBreaksRenderer(defaultSym, "clusterCount");
/*var picBaseUrl = "images/";
var blue = new PictureMarkerSymbol(picBaseUrl + "BluePin1LargeB.png", 32, 32).setOffset(0, 15);
var green = new PictureMarkerSymbol(picBaseUrl + "GreenPin1LargeB.png", 64, 64).setOffset(0, 15);
var red = new PictureMarkerSymbol(picBaseUrl + "RedPin1LargeB.png", 80, 80).setOffset(0, 15);*/
var style1 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 10,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([255,200,0]), 1),
new Color([255,200,0,0.8]));
var style2 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 25,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([255,125,3]), 1),
new Color([255,125,3,0.8]));
var style3 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 30,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([255,23,58]), 1),
new Color([255,23,58,0.8]));
var style4 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 35,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([204,0,184]), 1),
new Color([204,0,184,0.8]));
var style5 = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_CIRCLE, 40,
new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID,
new Color([0,0,255]), 1),
new Color([0,0,255,0.8]));
renderer.addBreak(0, 2, style1);
renderer.addBreak(2, 100, style2);
renderer.addBreak(100, 500, style3);
renderer.addBreak(500, 1000, style4);
renderer.addBreak(1000, 3001, style5);
clusterLayer.setRenderer(renderer);
map.addLayer(clusterLayer);
// close the info window when the map is clicked
map.on("click", cleanUp);
// close the info window when esc is pressed
map.on("key-down", function(e) {
if (e.keyCode === 27) {
cleanUp();
}
});
}
function cleanUp() {
map.infoWindow.hide();
clusterLayer.clearSingles();
}
});
</script>
</head>
<body>
<div id="map"></div>
</div>
</body>
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