Javascript 基于缩放级别显示WMS图层

我整天都在干这个，老实说，我已经没有主意了。我有一些WMS图层，我希望根据当前的缩放级别显示/不显示这些图层。是的，我已经浏览了API文档，它们看起来很清晰，但我遵循了所有建议，没有得到预期的结果：(

这是我看到的其中一个来源： http://trac.osgeo.org/openlayers/wiki/SettingZoomLevels

然后更糟糕的是，我发现如果你有一个开放的街道地图基础层在加载时显示，它似乎限制了你对地图numZoomLevels的控制，这正是我所需要的，因为我确实想使用它作为我的加载基础层

因此，我的问题是：

我做错了什么？ 在加载时使用开放式街道地图基础层时，是否真的没有解决缩放级别控制问题的方法？还是有什么我不知道的

以下是我的一些代码尝试： 拍摄1:tib_Lavels仅在缩放级别为8-10时显示，不起作用

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: null, //setting the map's zoom levels to null
            allOverlays: false
        }

var osm = new OpenLayers.Layer.OSM(); //MY base layer

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                );

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: 10, //setting the map's zoom levels to 10 only
            allOverlays: false
        }

var osm = new OpenLayers.Layer.OSM(); //MY base layer

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: null, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                )

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: 10, //setting the map's zoom levels to 10
            allOverlays: false
        }

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                );

假设2:tib_villages图层只应在缩放级别为8-10时显示，地图应仅具有10个缩放级别，但取而代之的是19个缩放级别，因为开放街道地图图层将其强制执行，不起作用

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: null, //setting the map's zoom levels to null
            allOverlays: false
        }

var osm = new OpenLayers.Layer.OSM(); //MY base layer

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                );

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: 10, //setting the map's zoom levels to 10 only
            allOverlays: false
        }

var osm = new OpenLayers.Layer.OSM(); //MY base layer

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: null, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                )

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: 10, //setting the map's zoom levels to 10
            allOverlays: false
        }

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                );

)

第3步：删除加载的开放街道地图基础层后，地图仅具有指定的10个缩放级别，但tib_村图层应仅在缩放级别为8-10时显示，不起作用

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: null, //setting the map's zoom levels to null
            allOverlays: false
        }

var osm = new OpenLayers.Layer.OSM(); //MY base layer

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                );

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: 10, //setting the map's zoom levels to 10 only
            allOverlays: false
        }

var osm = new OpenLayers.Layer.OSM(); //MY base layer

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: null, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                )

var options = {
                                        controls: [new OpenLayers.Control.Navigation()], //Needed to use GeoExt controls such as the zoomslider
            maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34),
            units: 'm',
            numZoomLevels: 10, //setting the map's zoom levels to 10
            allOverlays: false
        }

//MY overlay layer
var tib_villages = new OpenLayers.Layer.WMS(
                    "Villages", "http://localhost:8080/geoserver/wms", {layers: 'cite:tib_villages', transparent: true, numZoomLevels: 10, minZoomLevel: 8}, {isBaseLayer: false, displayInLayerSwitcher: true, visibility: true}
                );

衷心感谢您的所有建议

---

elshae

尝试使用

minResolution

和

maxResolution

而不是

minZoomLevel

。它通常工作正常。如果调用

map.getResolution（）

方法，可以获得任何缩放杠杆的分辨率

另一个选项是收听OpenLayers.Map的

zoomend

事件，并相应地切换图层可见性。类似如下：

map.events.on({ "zoomend": function (e) {
    if (this.getZoom() > 2) {
      layer1.setVisibility(false);
      layer2.setVisibility(true);
    }
    else {
      layer2.setVisibility(false);
      layer1.setVisibility(true);
    }
  }
});

---

我建议在图层上使用maxScale和minScale，而不是分辨率，但这可能是一个品味问题。：-）我不知道分辨率值，但从长远来看，分辨率很容易理解和维护，当别人看你的代码时。

@elshae：我会把你的问题贴在邮件列表上users@openlayers.org.Hmm我会去看看gis.stackexchange.com，然后在上面发帖Users@openlayers.org，但我经常没有得到回应：-/非常感谢！您的回答非常清晰简洁，现在我的地图功能正按照我的要求运行：Dclear解释，优雅的解决方案。工作做得无可挑剔。事实上，我最终还是得到了minScale:），太糟糕了，我不能把两个答案都标为正确：-/没关系。如果你能改变哪一个答案是正确的，那当然很好，但这没什么大不了的。如果你投了反对票，请提交评论，这样我将来可以改进。谢谢。我有点困惑，我什么时候投了反对票？我相信我最近接受了你的回答@艾尔莎我不知道谁投了反对票，我是在跟谁说话。显然不是你。：-）