Implement a back-to-top feature with a scroll button (Ionic 2 | Typescript)

Hello, I am currently working on incorporating a "scroll to top button" feature that includes the following requirements:

  1. Display the button once the user has scrolled down.
  2. Hide the button when the user scrolls back up.
  3. If the button is clicked, scroll the page to the top and then hide the button.

Any suggestions on how to implement this correctly would be greatly appreciated!

Thank you very much.

cordovatypescriptangularionic2

Answer №1

Streamlining the use of scrollToTop() method created by adriancarriger

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

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

  scrollToTop() {
    this.content.scrollToTop();
  }
}

Reference: http://ionicframework.com/docs/v2/api/components/content/Content/

Answer №2

Check out this Plunker Demo

Here are the steps to get this functionality working:

  • Create a function that will scroll your scroll-content element to the top
  • Monitor and keep track of the scroll position of your scroll-content
  • Utilize *ngIf on your scroll-to-top button to show it only when the scroll-content has scrolled past a certain threshold.

Function to Scroll to Top

I modified this Stack Overflow answer to suit the scroll-content element

scrollToTop(scrollDuration) {
let scrollStep = -this.ionScroll.scrollTop / (scrollDuration / 15);
let scrollInterval = setInterval( () => {
    if ( this.ionScroll.scrollTop != 0 ) {
        this.ionScroll.scrollTop = this.ionScroll.scrollTop + scrollStep;
    } else {
      clearInterval(scrollInterval);
    }
}, 15);

Tracking scroll-content Position

In this example, we use the window height as the benchmark for showing the scroll-to-top button:

this.ionScroll.addEventListener("scroll", () => {
  if (this.ionScroll.scrollTop > window.innerHeight) {
    this.showButton = true;
  } else {
    this.showButton = false;
  }
});

Button HTML Code

<button *ngIf="showButton" (click)="scrollToTop(1000)">Go to Top</button>

Complete TypeScript Component Code

import { NavController } from 'ionic-angular/index';
import { Component, OnInit, ElementRef } from "@angular/core";

@Component({
  templateUrl:"home.html"
})
export class HomePage implements OnInit {
  public ionScroll;
  public showButton = false;
  public contentData = [];

  constructor(public myElement: ElementRef) {}

  ngOnInit() {
    // Reference Ionic scroll element
    this.ionScroll = this.myElement.nativeElement.children[1].firstChild;
    
    // Function triggered on scroll event
    this.ionScroll.addEventListener("scroll", () => {
      if (this.ionScroll.scrollTop > window.innerHeight) {
        this.showButton = true;
      } else {
        this.showButton = false;
      }
    });
    
    // Populate content data
    for (let i = 0; i < 301; i++) {
      this.contentData.push(i);
    }
  }

  // Scroll to top function
  // Modified from https://stackoverflow.com/a/24559613/5357459
  scrollToTop(scrollDuration) {
    let scrollStep = -this.ionScroll.scrollTop / (scrollDuration / 15);
    let scrollInterval = setInterval( () => {
        if ( this.ionScroll.scrollTop != 0 ) {
            this.ionScroll.scrollTop = this.ionScroll.scrollTop + scrollStep;
        } else {
          clearInterval(scrollInterval);
        }
    }, 15);
  }

}

Entire Component HTML Structure

<ion-navbar primary *navbar>
  <ion-title>
    Ionic Framework Example
  </ion-title>
  <button *ngIf="showButton" (click)="scrollToTop(1000)">Go to Top</button>
</ion-navbar>

<ion-content class="has-header" #testElement>
  <div padding style="text-align: center;">
    <h1>Testing Ionic Framework</h1>
    <div *ngFor="let item of contentData">
      Test content-{{item}}
    </div>
  </div>
</ion-content>

Answer №3

Give this a shot. I hope it does the trick

import { Component, ViewChild } from '@angular/core';

import { Content } from 'ionic-angular';

@Component({...})

export class MyPage{

  @ViewChild(Content) content: Content;

  goToTop() {

    this.content.scrollToTop();
  }

}

Answer №4

After implementing adriancarriger's code, I successfully managed to adjust the Div element to be positioned at the top. Here is the code snippet that made it possible:

Html

<div  #Innholdtext >
<p> Add your content here to set scroll top </>
</div>

app.component.ts

import { Component, OnInit, ViewChild, ElementRef } from '@angular/core';

export class app implements OnInit {
    @ViewChild('Innholdtext') private hovedInnhold: ElementRef;
    private scrollElement;

    ngOnInit() {
        this.scrollElement = this.hovedInnhold.nativeElement;
        this.scrollElement.addEventListener("click", () =>{
            this.hovedInnhold.nativeElement.scrollTop = 0
        });
    }
}

Answer №5

Having a component nested within another component can sometimes cause issues with retrieving the inner content. In my situation, I needed to access the parent element in order to initiate a scroll when transitioning to the next slide.

This was particularly important for ensuring that the new slide starts at the top of the page.

 const container = document.querySelector(".slide-zoom");
      setTimeout(() => { if(container) container.scrollIntoView({ behavior: "smooth", block: "start" }) }, 200);

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