本文介绍了OpenLayers Cluster重新计算的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
所以，我在OpenLayers中聚集了许多项目。
So, I have a number of items clustered in OpenLayers.
我正在使用一种策略，根据属性对项目进行聚类。
I'm using a strategy that clusters the items based on their attributes.
我更改了项目的属性。
如何获得重新计算群集的群集策略？
How do I get the clustering strategy to recalculate the cluster?
推荐答案
好的，事实证明，自2.11RC1起，此功能在OpenLayers中不可用。因此，我自己将它实现为Cluster类的影子。该代码也可作为中的补丁提供。
Okay, so it turns out that this feature is not available in OpenLayers as of 2.11RC1. Therefore, I have implemented it as a shadow of the Cluster class myself. The code is also available as a patch in the OpenLayers Trac.
此答案末尾的代码可以直接删除到javascript文件中，并覆盖现有的OpenLayers OpenLayers.Strategy.Cluster 类。它添加了一个方法 recluster ，这个方法在调用时会导致策略重新计算其聚类。由于我们正在更改 Cluster 基类，因此任何派生类都应该适当地继承 recluster 方法。
The code at the end of this answer can be dropped directly into a javascript file and will override the existing OpenLayers OpenLayers.Strategy.Cluster class. It adds a method recluster which, when called, will cause the strategy to recalculate its clustering. Since we are altering the Cluster base class, any derived class should appropriately inherit the recluster method.
如何使用它的一个例子是：
An example of how to use this would be:
var clustering=new OpenLayers.Strategy.Cluster()
var vectorlayer = new OpenLayers.Layer.Vector('Vectorlayer', {
strategies: [clustering]
});
//ADD_LOTS_OF_FEATURES_TO_VECTOR_LAYER
clustering.distance=value;
clustering.recluster();
替换类的代码是：
OpenLayers.Strategy.Cluster = OpenLayers.Class(OpenLayers.Strategy, {
/**
* APIProperty: distance
* {Integer} Pixel distance between features that should be considered a
* single cluster. Default is 20 pixels.
*/
distance: 20,
/**
* APIProperty: threshold
* {Integer} Optional threshold below which original features will be
* added to the layer instead of clusters. For example, a threshold
* of 3 would mean that any time there are 2 or fewer features in
* a cluster, those features will be added directly to the layer instead
* of a cluster representing those features. Default is null (which is
* equivalent to 1 - meaning that clusters may contain just one feature).
*/
threshold: null,
/**
* Property: features
* {Array(<OpenLayers.Feature.Vector>)} Cached features.
*/
features: null,
/**
* Property: clusters
* {Array(<OpenLayers.Feature.Vector>)} Calculated clusters.
*/
clusters: null,
/**
* Property: clustering
* {Boolean} The strategy is currently clustering features.
*/
clustering: false,
/**
* Property: resolution
* {Float} The resolution (map units per pixel) of the current cluster set.
*/
resolution: null,
/**
* Constructor: OpenLayers.Strategy.Cluster
* Create a new clustering strategy.
*
* Parameters:
* options - {Object} Optional object whose properties will be set on the
* instance.
*/
/**
* APIMethod: activate
* Activate the strategy. Register any listeners, do appropriate setup.
*
* Returns:
* {Boolean} The strategy was successfully activated.
*/
activate: function() {
var activated = OpenLayers.Strategy.prototype.activate.call(this);
if(activated) {
this.layer.events.on({
"beforefeaturesadded": this.cacheFeatures,
"moveend": this.cluster,
scope: this
});
}
return activated;
},
/**
* APIMethod: deactivate
* Deactivate the strategy. Unregister any listeners, do appropriate
* tear-down.
*
* Returns:
* {Boolean} The strategy was successfully deactivated.
*/
deactivate: function() {
var deactivated = OpenLayers.Strategy.prototype.deactivate.call(this);
if(deactivated) {
this.clearCache();
this.layer.events.un({
"beforefeaturesadded": this.cacheFeatures,
"moveend": this.cluster,
scope: this
});
}
return deactivated;
},
/**
* Method: cacheFeatures
* Cache features before they are added to the layer.
*
* Parameters:
* event - {Object} The event that this was listening for. This will come
* with a batch of features to be clustered.
*
* Returns:
* {Boolean} False to stop features from being added to the layer.
*/
cacheFeatures: function(event) {
var propagate = true;
if(!this.clustering) {
this.clearCache();
this.features = event.features;
this.cluster();
propagate = false;
}
return propagate;
},
/**
* Method: clearCache
* Clear out the cached features.
*/
clearCache: function() {
this.features = null;
},
/**
* Method: cluster
* Cluster features based on some threshold distance.
*
* Parameters:
* event - {Object} The event received when cluster is called as a
* result of a moveend event.
*/
cluster: function(event) {
if((!event || event.zoomChanged || (event && event.recluster)) && this.features) {
var resolution = this.layer.map.getResolution();
if(resolution != this.resolution || !this.clustersExist() || (event && event.recluster)) {
this.resolution = resolution;
var clusters = [];
var feature, clustered, cluster;
for(var i=0; i<this.features.length; ++i) {
feature = this.features[i];
if(feature.geometry) {
clustered = false;
for(var j=clusters.length-1; j>=0; --j) {
cluster = clusters[j];
if(this.shouldCluster(cluster, feature)) {
this.addToCluster(cluster, feature);
clustered = true;
break;
}
}
if(!clustered) {
clusters.push(this.createCluster(this.features[i]));
}
}
}
this.layer.removeAllFeatures();
if(clusters.length > 0) {
if(this.threshold > 1) {
var clone = clusters.slice();
clusters = [];
var candidate;
for(var i=0, len=clone.length; i<len; ++i) {
candidate = clone[i];
if(candidate.attributes.count < this.threshold) {
Array.prototype.push.apply(clusters, candidate.cluster);
} else {
clusters.push(candidate);
}
}
}
this.clustering = true;
// A legitimate feature addition could occur during this
// addFeatures call. For clustering to behave well, features
// should be removed from a layer before requesting a new batch.
this.layer.addFeatures(clusters);
this.clustering = false;
}
this.clusters = clusters;
}
}
},
/**
* Method: recluster
* User-callable function to recluster features
* Useful for instances where a clustering attribute (distance, threshold, ...)
* has changed
*/
recluster: function(){
var event={"recluster":true};
this.cluster(event);
},
/**
* Method: clustersExist
* Determine whether calculated clusters are already on the layer.
*
* Returns:
* {Boolean} The calculated clusters are already on the layer.
*/
clustersExist: function() {
var exist = false;
if(this.clusters && this.clusters.length > 0 &&
this.clusters.length == this.layer.features.length) {
exist = true;
for(var i=0; i<this.clusters.length; ++i) {
if(this.clusters[i] != this.layer.features[i]) {
exist = false;
break;
}
}
}
return exist;
},
/**
* Method: shouldCluster
* Determine whether to include a feature in a given cluster.
*
* Parameters:
* cluster - {<OpenLayers.Feature.Vector>} A cluster.
* feature - {<OpenLayers.Feature.Vector>} A feature.
*
* Returns:
* {Boolean} The feature should be included in the cluster.
*/
shouldCluster: function(cluster, feature) {
var cc = cluster.geometry.getBounds().getCenterLonLat();
var fc = feature.geometry.getBounds().getCenterLonLat();
var distance = (
Math.sqrt(
Math.pow((cc.lon - fc.lon), 2) + Math.pow((cc.lat - fc.lat), 2)
) / this.resolution
);
return (distance <= this.distance);
},
/**
* Method: addToCluster
* Add a feature to a cluster.
*
* Parameters:
* cluster - {<OpenLayers.Feature.Vector>} A cluster.
* feature - {<OpenLayers.Feature.Vector>} A feature.
*/
addToCluster: function(cluster, feature) {
cluster.cluster.push(feature);
cluster.attributes.count += 1;
},
/**
* Method: createCluster
* Given a feature, create a cluster.
*
* Parameters:
* feature - {<OpenLayers.Feature.Vector>}
*
* Returns:
* {<OpenLayers.Feature.Vector>} A cluster.
*/
createCluster: function(feature) {
var center = feature.geometry.getBounds().getCenterLonLat();
var cluster = new OpenLayers.Feature.Vector(
new OpenLayers.Geometry.Point(center.lon, center.lat),
{count: 1}
);
cluster.cluster = [feature];
return cluster;
},
CLASS_NAME: "OpenLayers.Strategy.Cluster"
});
这篇关于OpenLayers Cluster重新计算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！