Question

很抱歉打扰你们，但我已经坚持了半天的问题。

我想使用LineString对象在OpenLayers中绘制多边形线，所以我从文档中复制了这个例子。它运行正常，但我看不到屏幕上的线

代码看起来像这样

      <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
    <head>
        <title></title>
    <script type="text/javascript"  src="http://openlayers.org/api/OpenLayers.js"></script>
    <script src="http://www.openstreetmap.org/openlayers/OpenStreetMap.js"></script>
    <script src='http://maps.google.com/maps?file=api&amp;v=2&amp;key=ABQIAAAAjpkAC9ePGem0lIq5XcMiuhR_wWLPFku8Ix9i2SXYRVK3e45q1BQUd_beF8dtzKET_EteAjPdGDwqpQ'></script> 

  <script type="text/javascript">    

var map;
var lineLayer ;
var points;
var style;

var polygonFeature
  function test()
  {
    lineLayer = new OpenLayers.Layer.Vector("Line Layer"); 
    style = { strokeColor: '#0000ff', 
                strokeOpacity: 1,
                strokeWidth: 10
    };

    map.addLayer(lineLayer);                    

    points = new Array();
    points[0] =new OpenLayers.LonLat(-2.460181,27.333984 ).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());;
    points[1] = new OpenLayers.LonLat(-3.864255,-22.5 ).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());;   
    var linear_ring = new OpenLayers.Geometry.LinearRing(points);
    polygonFeature = new OpenLayers.Feature.Vector(
            new OpenLayers.Geometry.Polygon([linear_ring]), null, style);
    lineLayer.addFeatures([polygonFeature]);
    alert("1");

  }

  function initialize() 
  {    
      map = new OpenLayers.Map ("map_canvas", {
            controls:[
                new OpenLayers.Control.Navigation(),
                new OpenLayers.Control.PanZoomBar(),
                new OpenLayers.Control.LayerSwitcher(),
                new OpenLayers.Control.Attribution()],
            maxExtent: new OpenLayers.Bounds(-20037508.34,-20037508.34,20037508.34,20037508.34),
            maxResolution: 156543.0399,
            numZoomLevels: 19,
            units: 'm',
            projection: new OpenLayers.Projection("EPSG:900913"),
            displayProjection: new OpenLayers.Projection("EPSG:4326")
          });

        // Define the map layer
        // Here we use a predefined layer that will be kept up to date with URL changes
        layerMapnik = new OpenLayers.Layer.OSM.Mapnik("Mapnik");
        map.addLayer(layerMapnik);
      var lonLat = new OpenLayers.LonLat(0, 0).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());
        map.zoomTo(3);
        map.setCenter(lonLat, 19);  

    test();
  }

  </script>
    </head>

    <body onload="initialize()" >

    <div id="map_canvas" style="width: 828px; height: 698px"></div>  
  </body>

</html>

我确定我在创建地图或其他东西时缺少一些参数，但我真的无法弄清楚哪一个。

Answer 1

你在这一行中忘记了's'字符：

lineLayer.addFeatures([lineFeature]);

功能'addFeature'不存在：OpenLayers.Layer.Vector.addFeatures

要查看此功能，请按住键盘上的Shift键并尝试绘制一个框

编辑：好的，现在我知道你是怎么想的。

您需要为数据库中的每个点创建一个OpenLayers.Point对象。一种解决方案是使用Ajax调用自己的PHP函数来检索它们。 PHP文件包含获取它们的代码。我建议以JSON格式返回它们（也许是一个字符串）。使用JQuery框架：

$.ajax({
   url: 'your_php_file.php',
   dataType: JSON // for example, you can use 'string' type too
   success: function(coordinates){

   }
});

现在您的数据库中有很多坐标。是时候绘制多边形了。以下链接可能很有用

OpenLayers - how do I draw a Polygon from existing lonLat points?

我希望它可以帮到你。快乐的编码！

<强> EDIT2 ：

linear_ring是一个属于OpenLayers.Geometry.LinearRing类的对象。 constructor需要一个OpenLayers.Geometry.Points数组，你给它的是OpenLayers.LonLat数组。

你需要修改这个在每个点创建后添加这一行（根据你自己的代码修改索引）：

points[0] = new OpenLayers.Geometry.Point(points[0].lon,points[0].lat);

所以你的测试函数如下所示：

function test(){
      lineLayer = new OpenLayers.Layer.Vector("Line Layer");
      style = { strokeColor: '#0000ff',
         strokeOpacity: 1,
         strokeWidth: 10
      };

      points = new Array();

      points[0] =new OpenLayers.LonLat(-2.460181,27.333984 ).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());;
      points[0] = new OpenLayers.Geometry.Point(points[0].lon,points[0].lat);

      points[1] = new OpenLayers.LonLat(-3.864255,-22.5 ).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());;
      points[1] = new OpenLayers.Geometry.Point(points[1].lon,points[1].lat);

      var linear_ring = new OpenLayers.Geometry.LinearRing(points);
      polygonFeature = new OpenLayers.Feature.Vector(
         new OpenLayers.Geometry.Polygon([linear_ring]), null, style);
         lineLayer.addFeatures([polygonFeature]);

      map.addLayer(lineLayer);

 }

结果如下：Image result

Answer 2

是的，OpenLayers可以以编程方式绘制线条。它甚至足够快，可以每秒多次绘制新线条，因此您可以显示实时数据或动画。无论如何，你的代码中有很多东西。也许你的风格搞砸了并且绘制了不可见的线条，或者你的数据点变得不正确并且线条离开了地图。无论如何，我建议这个简单的测试。

创建地图，然后添加矢量图层。挂在名为layerVec的全局变量中的矢量图层上。然后，运行此代码。

var CreateLine = function()
{

  var pList = new Array();
  for(var i=0; i<200; i++)
  {
    var p = new OpenLayers.Geometry.Point();
    p.x = i;
    p.y = i;
    pList.push(p);
  }
  var g = new OpenLayers.Geometry.LineString(pList);
  var f = new OpenLayers.Feature.Vector(g,null,null);
  layerVec.addFeatures(f);
};

不要担心坐标，这应该是地图中间的一条线。根据您的投影，它可能很小或很大，因此请放大。

打开图层LineString不起作用

2 个答案: