设置 OL-3
<link rel="stylesheet" href="http://openlayers.org/en/v3.17.1/css/ol.css" type="text/css">
<script src="http://openlayers.org/en/v3.17.1/build/ol.js"></script>
<link rel="stylesheet" href="http://openlayers.org/en/v3.17.1/css/ol.css" type="text/css">
<script src="http://openlayers.org/en/v3.17.1/build/ol.js"></script>