1. 不设置默认底图，第一个图层作为底图，然后叠加另外一个图层
先添加图层1，第一个图层1作为默认底图，然后在图层1上叠加图层2，并设置图层2的透明度为50%。
1 <!DOCTYPE html> 2 <html> 3 <head> 4 <title>simple demo</title> 5 <link rel="stylesheet" href="http://localhost:8003/arcgis_js_v320_api/library/3.20/3.20/esri/css/esri.css"> 6 <style type="text/css"> 7 html, body { margin: 0; padding: 0; height: 100%; width: 100%; } 8 #viewDiv { width: 100%; height: 100%; } 9 </style> 10 </head> 11 <body> 12 <div id="viewDiv"></div> 13 <script src="http://localhost:8003/arcgis_js_v320_api/library/3.20/3.20/init.js"></script> 14 <script type="text/javascript"> 15 require([ 16 "esri/map", 17 "esri/layers/ArcGISTiledMapServiceLayer", 18 "dojo/domReady!"], 19 function (Map, ArcGISTiledMapServiceLayer) { 20 var map = new Map("viewDiv"); 21 var tms1 = new ArcGISTiledMapServiceLayer("http://cache1.arcgisonline.cn/arcgis/rest/services/ChinaOnlineCommunity/MapServer"); //图层1 22 map.addLayer(tms1); 23 var tms2 = new ArcGISTiledMapServiceLayer("http://services.arcgisonline.com/arcgis/rest/services/Demographics/USA_Projected_Population_Change/MapServer", { "opacity": 0.5 }); //图层2，透明度50% 24 map.addLayer(tms2); 25 } 26 ); 27 </script> 28 </body> 29 </html>
效果如下：
