content.scrollTop is 0 unless I bind to (ionScroll)

Ionic Framework ionic-v3
1

Hi all,

I’m confused by some behaviour I am seeing in my ionic3 app, and wonder if anyone can help me understand what is going on.

The behaviour is:

I am importing ViewChild and Content

import { Component, ViewChild, NgZone } from '@angular/core';
import { NavController, NavParams, Content } from 'ionic-angular';

And then using them in a page:

export class MyPage {
	@ViewChild(Content) content: Content;

	constructor(
		public navCtrl: NavController,
		public navParams: NavParams,
		public zone: NgZone
	) {}
}

Confusingly, what I am seeing is this.content.scrollTop is 0 - unless in the HTML template I bind ionScroll to a function, like this:

<ion-content padding (ionScroll)="scrollHandler($event)">

scrollhandler can be an empty function:

scrollHandler() { /* Don't do anything */ }

If I bind to ionScroll in that way, this.content.scrollTop works as expected.

Does this make sense to anyone? I can’t see anything in the docs about it.