1、GeometryService的緩衝區（Buffer）功能實現

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1、建立地圖，並建立load的響應函數initToolbar

            map = new Map("map", {                basemap: "streets",                center: [-111.5, 39.541],                zoom: 7            });            map.on("load", initToolbar);        

2、initToolbar函數，啟用Draw對象，draw-end事件觸發時響應doBuffer函數

             function initToolbar(evtObj) {                app.tb = new Draw(evtObj.map);                app.tb.on("draw-end", doBuffer);            }    

3、dobuffer

   function doBuffer(evtObj) {                var geometry = evtObj.geometry,                map = app.map,                gsvc = app.gsvc;                switch (geometry.type) {                    case "point":                        var symbol = new SimpleMarkerSymbol(SimpleMarkerSymbol.STYLE_SQUARE, 10, new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID, new Color([255, 0, 0]), 1), new Color([0, 255, 0, 0.25]));                        break;                    case "polyline":                        var symbol = new SimpleLineSymbol(SimpleLineSymbol.STYLE_DASH, new Color([255, 0, 0]), 1);                        break;                    case "polygon":                        var symbol = new SimpleFillSymbol(SimpleFillSymbol.STYLE_NONE, new SimpleLineSymbol(SimpleLineSymbol.STYLE_DASHDOT, new Color([255, 0, 0]), 2), new Color([255, 255, 0, 0.25]));                        break;                }                var graphic = new Graphic(geometry, symbol);                map.graphics.add(graphic);                //setup the buffer parameters                var params = new BufferParameters();                params.distances = [dom.byId("distance").value];                params.bufferSpatialReference = new esri.SpatialReference({ wkid: dom.byId("bufferSpatialReference").value });                params.outSpatialReference = map.spatialReference;                params.unit = GeometryService[dom.byId("unit").value];                if (geometry.type === "polygon") {                    //if geometry is a polygon then simplify polygon.  This will make the user drawn polygon topologically correct.                    gsvc.simplify([geometry], function (geometries) {                        params.geometries = geometries;                        gsvc.buffer(params, showBuffer);                    });                } else {                    params.geometries = [geometry];                    gsvc.buffer(params, showBuffer);                }            }            function showBuffer(bufferedGeometries) {                var symbol = new SimpleFillSymbol(                  SimpleFillSymbol.STYLE_SOLID,                  new SimpleLineSymbol(                    SimpleLineSymbol.STYLE_SOLID,                    new Color([255, 0, 0, 0.65]), 2                  ),                  new Color([255, 0, 0, 0.35])                );                array.forEach(bufferedGeometries, function (geometry) {                    var graphic = new Graphic(geometry, symbol);                    app.map.graphics.add(graphic);                });                app.tb.deactivate();                app.map.showZoomSlider();            }