OnScroll Event is not working - Angular Dart

OnScroll Event is not working - Angular Dart



I have an issue with the window.onScroll event. The event was never triggered.


window.onScroll



That's my first try:


@override
void ngOnInit()

window.onScroll.listen((Event event) => print("it works.."));



But it's not working.



I basiclly need the onScroll event. Not more. So i tried the "old school" way in Html



My second try:


<div (scroll)="onScroll()">

<!--Some content-->

</div>



But it's also not working.



What is the best solution to get the scroll event in AngularDart?



By the way, i use AngularDart 5.






The JS way with (scroll)="onScroll()" is not expected to work. The first one looks better - you'll need to be sure that the ngOnInit is being executed. Note that if you're changing some binding in response to the scroll event angular won't pick it up unless you also tell angular to detect changes again.

– Nate Bosch
Sep 17 '18 at 22:11


(scroll)="onScroll()"


ngOnInit




2 Answers
2



There are multiple solutions to this problem.



The first thing that you need to do is get a reference to the HTML element that you want to get scroll events from. I pretend that this element looks like the following (in your components .html file):


.html



<div>Some scrollable content</div>


<div>Some scrollable content</div>



As far as I know, there are two ways of getting a reference to an HTML element in AngularDart.



First solution:



Use the @ViewChild annotation. For this to work, you need to add a template reference variable to the div. I call it "scrollable", however it is up to you how you will call it.


@ViewChild


div



<div #scrollable>Some scrollable content</div>


<div #scrollable>Some scrollable content</div>



Then add the following property to your component class:


@ViewChild("scrollable")
Element scrollable;



Second (but not recommended) solution:



Add an id to the div (the name of the id does not matter):
Get the reference to the div by using document.getElementById() provided by dart:html:


div


div


document.getElementById()


dart:html


Element scrollable = document.getElementById('scrollable')



The problem with this solution is, that document is not available in any of the AngularDart life cycle hooks as far as i know.


document



Finally, to listen to the onScroll stream of the scrollable element just do the following somewhere in your component class:


onScroll


scrollable


something.onScroll.listen((Event event) => print("Hurray, it works :)"))


div.onScroll.listen((ev)
);



this pretty much works on my tests.

Are you sure that the place you are adding the listener is the one that is in fact scrolling?






What is div in this case?

– Tobias Marschall
Sep 18 '18 at 14:51


div



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