Hi list,
I am using OpenLayers 2.13.1.
I am experiencing a problem when zoom in/out while OpenLayers is in process of
loading images from several WMS requests that resulted from a previous zoom
operation.
Uncaught TypeError: Cannot read property '_eventCacheID' of null
OpenLayers.debug.js:5178
OpenLayers.Event.observe
OpenLayers.debug.js:5178
tile.onLoadEnd
OpenLayers.debug.js:31046
OpenLayers.Events.OpenLayers.Class.triggerEvent
OpenLayers.debug.js:5812
OpenLayers.Tile.OpenLayers.Class.unload
OpenLayers.debug.js:29266
OpenLayers.Tile.Image.OpenLayers.Class.draw
OpenLayers.debug.js:29584
OpenLayers.Layer.Grid.OpenLayers.Class.initGriddedTiles
OpenLayers.debug.js:30957
OpenLayers.Layer.Grid.OpenLayers.Class.moveTo
OpenLayers.debug.js:30428
OpenLayers.Map.OpenLayers.Class.moveTo
OpenLayers.debug.js:9299
map.zoomTween.start.callbacks.done
OpenLayers.debug.js:9682
OpenLayers.Tween.OpenLayers.Class.stop
OpenLayers.debug.js:6697
OpenLayers.Tween.OpenLayers.Class.play
OpenLayers.debug.js:6730
(anonymous function)
OpenLayers.debug.js:615
loops.(anonymous function)
OpenLayers.debug.js:6528
I am having an extremely difficult time trying to determine what my app is
doing to make OpenLayers react this way. The effect of the error is that zoom
in/out capability breaks on the map until I reload the page.
Can someone enlighten me as to what may be going on here?
More background on the problem:
============================
One way I have been able to avoid the problem, although it is not an acceptable
solution, is to add the following code near the top of the
"OpenLayers.Event.observe" method:
if (element == null){
//console.log("element: " + element + ", name: " + name + ",
observer: " + observer + ", " + "useCapture: " + useCapture);
return;
}
Like this:
/**
* Method: observe
*
* Parameters:
* elementParam - {DOMElement || String}
* name - {String}
* observer - {function}
* useCapture - {Boolean}
*/
observe: function(elementParam, name, observer, useCapture) {
var element = OpenLayers.Util.getElement(elementParam);
useCapture = useCapture || false;
//Begin added lines
if (element == null){
//console.log("element: " + element + ", name: " + name + ",
observer: " + observer + ", " + "useCapture: " + useCapture);
return;
}
//End added lines
if (name == 'keypress' &&
(navigator.appVersion.match(/Konqueror|Safari|KHTML/)
|| element.attachEvent)) {
name = 'keydown';
}
//if observers cache has not yet been created, create it
if (!this.observers) {
this.observers = {};
}
//if not already assigned, make a new unique cache ID
if (!element._eventCacheID) { <===============
This is the line the error occurs because "element" is null
var idPrefix = "eventCacheID_";
if (element.id) {
idPrefix = element.id + "_" + idPrefix;
}
element._eventCacheID = OpenLayers.Util.createUniqueID(idPrefix);
}
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