MapXtreme for .net实现鼠标中键缩放地图

鼠标中键缩放地图要用到js,它的实现可以分为三步。

第一步，在页面的</form>之前添加如下JavaScript代码，（切忌一定要在</form>之前）

 

<script type="text/javascript">      
var Img = document.getElementById("MapControl1_Image");
if(Img != null)
{
  Img.attachEvent('onmousewheel', GetMouseWheelEvent);
}
function GetMouseWheelEvent()
{
    var mapImage = document.getElementById("MapControl1_Image");
    var url = "MapController.ashx?Command=WheelZoom&Width=" + mapImage.width +"&Height=" + mapImage.height
    + "&ExportFormat=" + mapImage.exportFormat + "&Ran=" + Math.random() + "&wheelvalue=" + event.wheelDelta;
    if (mapImage.mapAlias) 
        url +=  "&MapAlias=" + mapImage.mapAlias;    
    try 
    {
        mapImage.src = url;
    }
    catch(e)
    { 
        alert("Error!");
    }
}
</script>

第二步，在后台代码中，如自定义命令的文件CustomCommands.cs中的添加如下类：

 

    [Serializable]
    public class WheelZoom : MapBaseCommand
    {
        public WheelZoom()
        {
            Name = "WheelZoom";
        }

        public override void Process()
        {
            int wheelvalue = int.Parse(System.Convert.ToString(HttpContext.Current.Request["wheelvalue"]));
          
            MapControlModel model = MapControlModel.GetModelFromSession();
            model.SetMapSize(MapAlias, MapWidth, MapHeight);
            try
            {
                MapInfo.Mapping.Map map = model.GetMapObj(MapAlias);

                MapInfo.Geometry.Distance d;
                if (wheelvalue > 0)
                {
                    d = new MapInfo.Geometry.Distance(map.Zoom.Value * 0.5, map.Zoom.Unit);
                }
                else
                {
                    d = new MapInfo.Geometry.Distance(map.Zoom.Value * 2, map.Zoom.Unit);
                }
                map.Zoom = d;
            }
            finally
            {
                System.IO.MemoryStream ms = model.GetMap(MapAlias, MapWidth, MapHeight, ExportFormat);
                StreamImageToClient(ms);
            }
        }
    }

 

 

第三步,在页面注册WheelZoom

if(Session.IsNewSession)
{
    MapControlModel model = MapControlModel.SetDefaultModelInSession();
    model.Commands.Add(new WheelZoom());
}