概述:
本文讲述如何在openlayers中实现画圆。
效果:
实现思路:
1、画中心点
通过OpenLayers.Control.DrawFeature和OpenLayers.Handler.Point实现在地图上画圆心。
2、移动鼠标设置半径
画点结束后,激活地图的鼠标移动事件,获取圆心到鼠标点的距离,并画圆,将结果展示到地图上。
3、点击地图结束绘制
点击地图,结束绘制,将最终结果展示到地图上,并停止地图的鼠标移动事件。
实现代码:
<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>china EPSG:4326 image/png</title> <link rel="stylesheet" type="text/css" href="http://localhost/olapi/theme/default/style.css"/> <style type="text/css"> body { font-family: sans-serif; font-weight: bold; font-size: .8em; } body { border: 0px; margin: 0px; padding: 0px; } #map { width: 100%; height: 100%; border: 0px; padding: 0px; } .query-box{ position: absolute; top: 15pt; right: 15pt; z-index:1001; border: 1px solid #ff0000; border-radius: 3px; background: #f2f2f2; padding: 5px 8px; font-family: "Trebuchet MS", Helvetica, Arial, sans-serif; } </style> <script type="text/javascript" src="http://localhost/olapi/OpenLayers.js"></script> <script type="text/javascript" src="http://localhost/olapi/lib/OpenLayers/Lang/zh-CN.js"></script> <script src="http://localhost/jquery/jquery-1.8.3.js"></script> <script src="circle.js"></script> <script type="text/javascript"> var map, wfs; function init(){ var bounds = new OpenLayers.Bounds( 87.57582859314434, 19.969920291221204, 126.56713756740385, 45.693810203800794 ); var options = { controls: [], maxExtent: bounds, maxResolution: 0.1523098006807012, projection: "EPSG:4326", units: 'degrees' }; map = new OpenLayers.Map('map', options); var tiled = new OpenLayers.Layer.WMS( "province", "http://localhost:8081/geoserver/lzugis/wms", { "LAYERS": 'province', "STYLES": '', format: 'image/png' }, { buffer: 0, displayOutsideMaxExtent: true, isBaseLayer: true, yx : {'EPSG:4326' : true} } ); map.addLayer(tiled); map.addControl(new OpenLayers.Control.PanZoomBar({ position: new OpenLayers.Pixel(2, 15) })); map.addControl(new OpenLayers.Control.Navigation()); map.zoomToExtent(bounds); var drawLayer = new OpenLayers.Layer.Vector("drawLayer",{ styleMap: new OpenLayers.StyleMap() }); var showLayer = new OpenLayers.Layer.Vector("showLayer",{ styleMap: new OpenLayers.StyleMap({'default':{ strokeColor: "#ff0000", strokeOpacity: 1, strokeWidth: 1, fillColor: "#000000", fillOpacity: 0.1 }}) }); map.addLayers([drawLayer,showLayer]); var drawCtrl = new OpenLayers.Control.DrawFeature(drawLayer, OpenLayers.Handler.Point); map.addControl(drawCtrl); drawCtrl.featureAdded = onEndDraw; function onEndDraw(feature){ drawCtrl.deactivate(); drawLayer.setVisibility(true); var start = feature.geometry; drawLayer.addFeatures(start); var circle,moveEvt; map.events.register("mousemove",map,function(e){ moveEvt = e; drawLayer.removeAllFeatures(); var pt = map.getLonLatFromPixel(new OpenLayers.Pixel(e.x, e.y)); var end = new OpenLayers.Geometry.Point(pt.lon, pt.lat); var line = new OpenLayers.Geometry.LineString([start, end]); var radius = line.getLength(); var geometry = createCircle(start,radius,100,0); var feature = new OpenLayers.Feature.Vector(geometry); circle = feature; drawLayer.addFeatures(feature); }); map.events.register("click",map,function(e){ showLayer.removeAllFeatures(); showLayer.addFeatures(circle); drawLayer.setVisibility(false); }); } $("#draw").on("click",function(){ drawLayer.removeAllFeatures(); showLayer.removeAllFeatures(); drawCtrl.activate(); }); } </script> </head> <body onLoad="init()"> <div class="query-box"> <button id="draw">画圆</button> </div> <div id="map"></div> </body> </html>
在上文中用到了createCircle,该函数如下:
/** * Method: createCircle * Create a regular polygon around a radius. Useful for creating circles * and the like. * * Parameters: * origin - {<OpenLayers.Geometry.Point>} center of polygon. * radius - {Float} distance to vertex, in map units. * sides - {Integer} Number of sides. 20 approximates a circle. * rotation - {Float} original angle of rotation, in degrees. */ function createCircle(origin, radius, sides, rotation) { var angle = Math.PI * ((1/sides) - (1/2)); if(rotation) { angle += (rotation / 180) * Math.PI; } var rotatedAngle, x, y; var points = []; for(var i=0; i<sides; ++i) { rotatedAngle = angle + (i * 2 * Math.PI / sides); x = origin.x + (radius * Math.cos(rotatedAngle)); y = origin.y + (radius * Math.sin(rotatedAngle)); points.push(new OpenLayers.Geometry.Point(x, y)); } var ring = new OpenLayers.Geometry.LinearRing(points); return new OpenLayers.Geometry.Polygon([ring]); };
时间: 2024-10-03 07:36:11