topic Re: map.centerAndZoom deferred in ArcGIS JavaScript Maps SDK Questions

map.centerAndZoom deferred

TimWitt2 — Thu, 28 Jan 2016 18:13:47 GMT

Good afternoon everybody,

In my webapp I use the map centerAndZoom method Map | API Reference | ArcGIS API for JavaScript which will return a deferred.

I haven't worked with deferred before and was wondering how I can continue with my code once the centerAndZoom has finished.

Would it look something like this or can somebody (probably Robert) give me an example?

map.centerAndZoom(allPoints[0].geometry,8).then(function(){

//continuation of the code

});

Thanks,

Tim

Re: map.centerAndZoom deferred

RobertScheitlin__GISP — Thu, 28 Jan 2016 18:29:17 GMT

Tim,

That is it exactly.

Re: map.centerAndZoom deferred

ReneRubalcava — Thu, 28 Jan 2016 18:29:33 GMT

Yeah, centerAndZoom returns a Promise, which comes from the Deferred. This means you can use the "then()" method as your sample shows to continue your code.

Re: map.centerAndZoom deferred

TimWitt2 — Thu, 28 Jan 2016 18:33:10 GMT

Thank you, since I've never dealt with deferred, I figured I ask to make sure I understand it.

Re: map.centerAndZoom deferred

TONGSUN — Thu, 06 Dec 2018 23:21:40 GMT

Well, I tried to add a flash point marker graphic in both ways when !this.map.extent.contains(zoomExtent):

this.map.centerAt(zoomExtent).then(DoFlash());

new Promise(function(resolve, reject) {

this.map.centerAt(zoomExtent);

}).then(DoFlash());

I got error message 'Uncaught lang.hitch: scope["setStroke"] is null (scope="[object Window]")'. But no problem DoFlash() if the map doesn't need to be re-centered.

Please help.

Thanks!

Re: map.centerAndZoom deferred

TONGSUN — Thu, 06 Dec 2018 23:28:38 GMT

Robert, I tried to add a flash point marker graphic in both ways when !this.map.extent.contains(zoomExtent):

this.map.centerAt(zoomExtent).then(DoFlash());

new Promise(function(resolve, reject) {

this.map.centerAt(zoomExtent);

}).then(DoFlash());

I got error message 'Uncaught lang.hitch: scope["setStroke"] is null (scope="[object Window]")'. But no problem DoFlash() if the map doesn't need to be re-centered.

Please help, thanks!

Re: map.centerAndZoom deferred

RobertScheitlin__GISP — Fri, 07 Dec 2018 02:57:13 GMT

Tong,

Because you have this.map I have to assume that your issue is a scope issue and your code should look like:

this.map.centerAt(zoomExtent).then(lang.hitch(this, DoFlash));‍‍‍

Re: map.centerAndZoom deferred

TONGSUN — Mon, 10 Dec 2018 19:45:10 GMT

Robert,

Thanks for your advice. I tried your suggestion of "this.map.centerAt(zoomExtent).then(lang.hitch(this, DoFlash()));"

Then I tried "map.centerAt(zoomExtent).then(lang.hitch(this, DoFlash()));"

I still got the same error message.

Basically, I need to make sure DoFlash() happens after the map is re-centered. But when I put "alert" at the beginning of DoFlash(), the map exent has not changed yet.

Re: map.centerAndZoom deferred

RobertScheitlin__GISP — Mon, 10 Dec 2018 20:14:28 GMT

Tong,

I updated my code suggestion.

When you have

this.map.centerAt(zoomExtent).then(lang.hitch(this, DoFlash()));‍

the DoFlash() means call the function immediately when the code is parsed.

You need:

this.map.centerAt(zoomExtent).then(lang.hitch(this, DoFlash));‍

Re: map.centerAndZoom deferred

TONGSUN — Mon, 10 Dec 2018 20:29:36 GMT

Thank you so much! It works now.

I would probably try bunch of other things before even thinking about there is difference between these two.