OpenLayers 3：删除事件监听器

Question

In Openlayers 3 how to remove a event listener attached like this:

var a = map.on("pointerdrag",function (e) {
             // event handler
});

var b = map.on("pointerdrag",function (e) {
             // event handler
});

How do I remove only listner a and keep b active?

Answer 1

Ah its pretty simple! Its in the API Docs : unByKey , but very counter-intuitive name for an off function.

So to remove the event listener a :

map.unByKey(a);

Will remove a listener but keep the b on.

Note: this will work across any object in Open Layers 3 that emits an event. like Layers, Interactions etc..

Answer 2

I was just wondering the same thing, seems like off would be the appropriate method to remove an event listener. You can also call this directly in the event callback:

map.on("pointerdrag", function (e) {
    map.unByKey(e);
});

This should remove only the this specific event.