Arcgis for JS之对象捕捉

在web操作，如绘制或者测量的时候，为了精确，需要捕捉到某一图层的对象，在此，讲解下如何在Arcgis for JS中实现捕捉对象。首先，在地图中添加一个graphiclayer：

            gLayer = new GraphicsLayer();
            map.addLayer(gLayer);

接着，在gLayer中添加几个对象：

            map.on("load",function(){
                var items = geometry.item;
                gLayer.add(new Graphic(WktToPoint(items[0].wkt, {"wkid":4326}),sms));
                gLayer.add(new Graphic(WktToPolyline(items[1].wkt, {"wkid":4326}),sls));
                gLayer.add(new Graphic(WktToPolygon(items[2].wkt, {"wkid":4326}),sfs));
            });

接下来，定义drawtoolbar以及绘制完成后的事件：

            var drawToolbar = new esri.toolbars.Draw(map,{tooltip: "place text"});
            drawToolbar.on("draw-end",showDrawResults);
            function showDrawResults(evt){
                drawToolbar.deactivate();
                map.setMapCursor("default");
                var geometry = evt.geometry;
                map.graphics.add(new Graphic(geometry,sls));
            };

接下来，定义一个Button，并添加button的click事件：

<button id="draw" style="z-index: 99;">绘制图形</button>

            on(dom.byId("draw"), "click", function(){
                drawToolbar.activate(esri.toolbars.Draw.POLYLINE);
            });

接下来定义map的捕捉设置：

            var snapManager = map.enableSnapping({
                snapKey:has("mac") ? keys.META : keys.CTRL
            });
            var layerInfos = [{layer: gLayer}];
            snapManager.setLayerInfos(layerInfos);

备注：

此处，需要调用的dojo包包括：

        require([
            "esri/map",
            "esri/layers/GraphicsLayer",
            "esri/graphic",
            "esri/SnappingManager",
            "esri/sniff",

            "dojo/_base/event",
            "dojo/on",
            "dojo/dom",
            "dojo/keys",
            "dojo/domReady!"],
        function(Map, GraphicsLayer, Graphic, Point, SnappingManager, has,
                 event, on,dom, keys) {

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