强制OpenLayers Markers图层在顶部绘制，并在下面有可选择的图层 [英] Forcing an OpenLayers Markers layer to draw on top, and having selectable layers beneath

问题描述

我有一个OpenLayers地图，其中包含光栅基础层，矢量图层和标记图层。它们以正确的顺序显示，矢量顶部的标记很好。

I have an OpenLayers map with a raster base layer, a vector layer and a markers layer in that order. They display fine, in the correct order with the markers on top of the vectors, great.

但是当我添加一个SelectFeature控件并将其指向矢量图层时，它尽管已经努力提高标记层或设置Z指数，但突然在标记层上方绘制。似乎SelectFeature控件会覆盖所有绘图顺序设置。这是设计，还是我能以某种方式克服这个？

But when I add a SelectFeature Control and point it to the vector layer, it is suddenly drawn above the markers layer, despite all efforts to raise the marker layer or setting the Z index. It seems that the SelectFeature control overrides all drawing order settings. Is this by design, or can I overcome this somehow?

图层定义：

var baselayer = new OpenLayers.Layer.WMS('Norden', 
'http://{myarcgisserver}/ArcGIS/services/mylayer/MapServer/WMSServer', {
    layers :'1,2',
    transparent :false,
    width :'auto',
    height :'auto',
    filter :null
}, {
    isBaseLayer: true,
    singleTile :true,
    ratio :1,
    alpha :false,
    transitionEffect :'resize'
});

var vectorLayer = new OpenLayers.Layer.Vector("Work orders", {
    projection: new OpenLayers.Projection("EPSG:2400"),
    strategies: [new OpenLayers.Strategy.Fixed(), refresh],
    protocol: new OpenLayers.Protocol.HTTP({
        url: "/WorkOrder/WorkOrders.ashx?output=geojson",
        format: new OpenLayers.Format.GeoJSON()
    })
});

var markerlayer = new OpenLayers.Layer.Markers("Markers", {
    projection: new OpenLayers.Projection("EPSG:2400"),
    displayInLayerSwitcher: false
}
);

控制定义：

var selectctrl = new OpenLayers.Control.SelectFeature(
    vectorLayer,
    {
        clickout: true,
        toggle: false,
        multiple: false,
        hover: false,
        toggleKey: "ctrlKey", // ctrl key removes from selection
        multipleKey: "shiftKey", // shift key adds to selection
        box: false
    }
);

激活:(如果没有这个，图层绘制的顺序正确）

Activation: (Without this, the layers draw in correct order)

map.addControl(selectctrl);

selectctrl.activate();

编辑：
在OpenLayers.Handler.Feature中找到这个，其中moveLayerToTop感觉像罪魁祸首......会试图克服它，但如果有人知道这是不可能的，请告诉我！

Found this in OpenLayers.Handler.Feature, where the "moveLayerToTop" feels like the culprit... Will try to overcome it, but if someone knows it to be impossible, please let me know!

/**
 * Method: activate 
 * Turn on the handler.  Returns false if the handler was already active.
 *
 * Returns:
 * {Boolean}
 */
activate: function() {
    var activated = false;
    if(OpenLayers.Handler.prototype.activate.apply(this, arguments)) {
        this.moveLayerToTop();
        this.map.events.on({
            "removelayer": this.handleMapEvents,
            "changelayer": this.handleMapEvents,
            scope: this
        });
        activated = true;
    }
    return activated;
},

推荐答案

答案 - 如果是好吧把它叫做我上面提到的激活功能。我试图覆盖它并删除了对moveLayerToTop的调用，它就像一个魅力。

The answer - if it's ok to call it that lies in the activate function that I mention above. I tried to override that and removed the call to moveLayerToTop, and it works like a charm.

编辑：
我最终将此代码添加到OL代码库外的js文件中，覆盖处理程序激活功能。这是因为否则我将失去对OpenLayers代码库更新的更改。

EDIT: I ended up adding this code to a js file outside the OL code library, overriding the handlers activate function. This is because I would otherwise lose the change on an update of the OpenLayers code base.

OpenLayers.Handler.Feature.prototype.activate = function() {
    var activated = false;
    if (OpenLayers.Handler.prototype.activate.apply(this, arguments)) {
        //this.moveLayerToTop();
        this.map.events.on({
            "removelayer": this.handleMapEvents,
            "changelayer": this.handleMapEvents,
            scope: this
        });
        activated = true;
    }
    return activated;
};

这篇关于强制OpenLayers Markers图层在顶部绘制，并在下面有可选择的图层的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！