topic Re: How to disable an "on" event? in Web AppBuilder Custom Widgets Questions

How to disable an "on" event?

PavelVeselský1 — Sun, 12 Dec 2021 08:37:38 GMT

The only way I know to disable (or better, remove, I don't need to re-enable it) an on event in dojo is to use a handle, like this:

var myUnload = map.on("unload", unloadHandler); 
myUnload.remove();

In Web AppBuilder, event handlers are supposed to be made through this.own, at least this method is used in all the widgets by ESRI. How to disable such events? Setting a handle doesn't seem possible.

What exactly does this.own do? If I understand it right, it should save the event somewhere into the widget. But where? How can I remove it from there?

Re: How to disable an "on" event?

RobertScheitlin__GISP — Tue, 12 Apr 2016 13:14:51 GMT

Pavel,

This.own is a way for a widget to destroy/remove events when the widget it destroyed.

The advantage of using own() in the widget infrastructure is that internally, the widget can keep track of all of its handles, and make sure everything is disconnected and/or unsubscribed when the widget is destroyed—preventing any kind of memory leaks.

You can use JS removeEventListener in modern browsers if you know the event and function that the event is calling:

node.removeEventListener ("click", clickFunction, false);

Re: How to disable an "on" event?

PavelVeselský1 — Tue, 12 Apr 2016 14:20:17 GMT

I can't get it to work - the event is over this.map which is not a DOM node and thus doesn't contain removeEventListener, or misses the right node (I tried this.map.container.removeEventListener("click", this.onMapClick, true);). The function this.onMapClick still runs when it shouldn't.

But thanks for pointing to this function, Robert!

Re: How to disable an "on" event?

RobertScheitlin__GISP — Tue, 12 Apr 2016 14:27:12 GMT

Pavel,

I doubt that it would work but,

this.map.domNode.removeEventListener("click", this.onMapClick, true);

may be worth a try.

Re: How to disable an "on" event?

KenBuja — Tue, 12 Apr 2016 16:08:50 GMT

Can you use the pausable method of "dojo/on", since its target doesn't need to be a DOM node?

...the target object (a DOM node or other event emitting object) that will be the source of the event. The target object may be a host object with its own event capabilities (like DOM elements or the window), or it may be a JavaScript object with an on() method.

Re: How to disable an "on" event?

RobertScheitlin__GISP — Tue, 12 Apr 2016 16:19:09 GMT

Pavel,

OK, I slowed down and re-read your original post a couple of time and I think what you are wanting is achieved by this code:

this.own(this.mapClickEvent = this.map.on('click', lang.hitch(this, this.mapClickEvtHandler)));

Re: How to disable an "on" event?

PavelVeselský1 — Wed, 13 Apr 2016 05:44:20 GMT

It needs some handler which I didn't have, so I accepted Robert's answer as "correct". In practice, I will use your answer as well, reusing listeners is a good practice and my case it will be very helpful. Thanks, Ken!