ng-bootstrap collapse: How to apply animations?

Question

I\'m using Collapse: https://ng-bootstrap.github.io/#/components/collapse

However, it does not animate; even not on the demo site. How should I implement this??

Answer 1

I've created a directive using only bootstrap classes that performs the same original bootstrap effect using only angular-animation, check it out!

Live example

Directive code

import {Directive, ElementRef, HostBinding, Input, OnChanges, OnInit, SimpleChanges} from '@angular/core';
import {animate, AnimationBuilder, AnimationPlayer, keyframes, style} from '@angular/animations';

@Directive({
  selector: '[appCollapseAnimated]'
})
export class CollapseAnimatedDirective implements OnChanges, OnInit {
  private static readonly SHOW_STYLE = 'show';
  private static readonly COLLAPSING = 'collapsing';

  @Input('appCollapseAnimated')
  collapsed = true;

  @Input()
  skipClosingAnimation = false;

  @HostBinding('class.collapse')
  private readonly addCollapseClass = true;

  private currentEffect: AnimationPlayer;
  private _closeEffect: AnimationPlayer;
  private _openEffect: AnimationPlayer;

  constructor(private el: ElementRef,
              private builder: AnimationBuilder) {

  }

  ngOnInit(): void {
    if (!this.collapsed) {
      this.getClassList().add(CollapseAnimatedDirective.SHOW_STYLE);
    }
  }

  private get openEffect(): AnimationPlayer {
    if (!this._openEffect) {
      this._openEffect = this.builder.build(animate('500ms', keyframes([
        style({height: '0'}),
        style({height: '*'}),
      ]))).create(this.el.nativeElement);
    }
    this._openEffect.onDone(() => this.effectDone());
    return this._openEffect;
  }


  private get closeEffect(): AnimationPlayer {
    if (!this._closeEffect) {
      this._closeEffect = this.builder.build(animate('500ms', keyframes([
        style({height: '*'}),
        style({height: '0'}),
      ]))).create(this.el.nativeElement);
    }
    this._closeEffect.onDone(() => this.effectDone());
    return this._closeEffect;
  }

  private effectDone() {
    if (this.collapsed) {
      this.getClassList().remove(CollapseAnimatedDirective.SHOW_STYLE);
    }
    this.getClassList().remove(CollapseAnimatedDirective.COLLAPSING);
    if (this.currentEffect) {
      this.currentEffect.reset();
      this.currentEffect = null;
    }
  }

  ngOnChanges(changes: SimpleChanges): void {
    if (changes.collapsed && !changes.collapsed.firstChange) {
      if (changes.collapsed.previousValue === true && changes.collapsed.currentValue === false) {
        this.startOpening();
      }
      if (changes.collapsed.previousValue === false && changes.collapsed.currentValue === true) {
        this.startClosing();
      }
    }
  }

  private startOpening(): void {
    this.getClassList().add(CollapseAnimatedDirective.SHOW_STYLE);
    const effect = this.openEffect;
    this.playEffect(effect);
  }

  private getClassList() {
    const nativeElement = this.el.nativeElement as HTMLElement;
    return nativeElement.classList;
  }

  private startClosing(): void {
    const effect = this.closeEffect;
    if (this.skipClosingAnimation) {
      this.effectDone();
    } else {
      this.playEffect(effect);
    }
  }

  private playEffect(effect: AnimationPlayer) {
    if (!this.currentEffect) {
      this.getClassList().add(CollapseAnimatedDirective.COLLAPSING);
      this.currentEffect = effect;
      this.currentEffect.play();
    }
  }
}

Use it in your template:

  Toggle


  this should collapse with the default bootstrap behaviour