Angular Stagger Animation for multiple new elements

问题

I'm trying to have a stagger animation in a list. Up till now I have managed to have the stagger animation on load. Apart from on load I'd like to have the stagger animation trigger when new items are added to the array.

I followed this example: https://medium.com/google-developer-experts/angular-applying-motion-principles-to-a-list-d5cdd35c899e

And came up with a quick test: https://stackblitz.com/edit/angular-stagger-animation-test2

In the app.component.ts I define the stagger animation and in the child.component.ts I define the element's animation.

Stagger Animation:

trigger('list', [
    transition(':enter', [
        query('@animate',
            stagger(250, animateChild())
        )
    ])
])

The query('@animate') gets the child component element, with the animateChild() triggering the animation in the child component.

Child Animation:

trigger('animate', [
  transition(':enter', [
    style({ opacity: 0, transform: 'translateY(-10px)' }),
    animate('250ms', style({ opacity: 1, transform: 'translateY(0px)' }))
  ]),
  transition(':leave', [
    style({ opacity: 1 }),
    animate('250ms', style({ opacity: 0, transform: 'translateY(10px)' }))
  ])
])

The main difference in my case is that I'm adding multiple objects to the array at once. I don't know if it possible to have the new items enter the page in a staggered manner.

回答1:

I managed to solve this by changing the parent animation like so:

trigger('list', [
  transition('* => *', [
    query(':enter',
      stagger(250, animateChild())
    )
  ])
])

So the transition will trigger on any state not just when the list is in the "enter" state. Furthermore, the query now checks for ':enter' which means that it will get any new elements that enter the list.

To trigger the animation I am saving the components in a list and so on every change in the list the animation triggers.

Parent Template

<div [@list]="list.length">
  ....
</div>

Updated stackblitz

https://stackblitz.com/edit/angular-stagger-animation-test2

References:

• https://www.yearofmoo.com/2017/06/new-wave-of-animation-features.html#using-query-and-stagger

• https://stackoverflow.com/a/47834376/2312637

来源：https://stackoverflow.com/questions/52501138/angular-stagger-animation-for-multiple-new-elements