Smooth vue collapse transition on v-if

Question

I'm struggling with vue transitions trying to show / hide content using v-if smoothly. Whilst I understand the css classes and transitions, I can make the content appear 'smoothly' using things like opacity or translation etc...but once the animation is complete (or rather as it starts), any html sections below seem to 'jump'.

I'm trying to achieve the same affect as the Bootstrap 4 'collapse' class - click one of the top buttons here: https://getbootstrap.com/docs/4.0/components/collapse/

As the hidden section appears / disappears, all the html content 'slides' nicely with it.

Is this possible using Vue transition for content being shown using v-if? All the samples on the vue transitions docs, whilst having great css transition effects, have the below html 'jump' once the transition has started or is complete.

I've seen some pure js solutions using max-height - https://jsfiddle.net/wideboy32/7ap15qq0/134/

and tried with vue: https://jsfiddle.net/wideboy32/eywraw8t/303737/

.smooth-enter-active, .smooth-leave-active {
  transition: max-height .5s;
}
.smooth-enter, .smooth-leave-to {
  max-height: 0 .5s;
}

Thanks!

Answer 1

i also had similar task. I found that it isn't possible to do it without JS. So i write custom transition component ( Reusable Transitions ) and it works for me:

Vue.component('transition-collapse-height', {
  template: `<transition
    enter-active-class="enter-active"
    leave-active-class="leave-active"
    @before-enter="beforeEnter"
    @enter="enter"
    @after-enter="afterEnter"
    @before-leave="beforeLeave"
    @leave="leave"
    @after-leave="afterLeave"
  >
    <slot />
  </transition>`,
  methods: {
    /**
     * @param {HTMLElement} element
     */
    beforeEnter(element) {
      requestAnimationFrame(() => {
        if (!element.style.height) {
          element.style.height = '0px';
        }

        element.style.display = null;
      });
    },
    /**
     * @param {HTMLElement} element
     */
    enter(element) {
      requestAnimationFrame(() => {
        requestAnimationFrame(() => {
          element.style.height = `${element.scrollHeight}px`;
        });
      });
    },
    /**
     * @param {HTMLElement} element
     */
    afterEnter(element) {
      element.style.height = null;
    },
    /**
     * @param {HTMLElement} element
     */
    beforeLeave(element) {
      requestAnimationFrame(() => {
        if (!element.style.height) {
          element.style.height = `${element.offsetHeight}px`;
        }
      });
    },
    /**
     * @param {HTMLElement} element
     */
    leave(element) {
      requestAnimationFrame(() => {
        requestAnimationFrame(() => {
          element.style.height = '0px';
        });
      });
    },
    /**
     * @param {HTMLElement} element
     */
    afterLeave(element) {
      element.style.height = null;
    },
  },
});

new Vue({
  el: '#app',
  data: () => ({
    isOpen: true,
  }),
  methods: {
    onClick() {
      this.isOpen = !this.isOpen;
    }
  }
});

.enter-active,
.leave-active {
  overflow: hidden;
  transition: height 1s linear;
}

.content {
  background: grey;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <button @click="onClick">
    open/hide
  </button>
  <transition-collapse-height>
   <div v-show="isOpen" class="content">
     <br/>
     <br/>
     <br/>
     <br/>
   </div>
  </transition-collapse-height>
</div>

Answer 2

If you want to animate max-height, then you should enter the amount of max-height for the element you want to animate, also correct the second class as you put 's' (or seconds) in max-height definition :

p{
  max-height: 20px;
}
.smooth-enter-active, .smooth-leave-active {
  transition: max-height .5s;
}
.smooth-enter, .smooth-leave-to {
  max-height: 0;
}

if you want something like bs4 collapse then the example inside vue website will do :

.smooth-enter-active, .smooth-leave-active {
  transition: opacity .5s;
}
.smooth-enter, .smooth-leave-to {
  opacity: 0
}

Edit : What you are trying to do is achievable by first finding out the height of the content and then setting it inside .*-enter-to and .*-leave classes. One way to do that is demonstrated in fiddle below :

https://jsfiddle.net/rezaxdi/sxgyj1f4/3/

You can also completely forget about v-if or v-show and just hide the element using height value which I think is a lot smoother :

https://jsfiddle.net/rezaxdi/tgfabw65/9/

Answer 3

Here is my Vue3 solution based on Web Animation API, see demo It is rather similar to the one by Alexandr Vysotsky posted here before, but this one will also preserve the initial height of the block.

I started with this blog post and somehow improved it (mostly to keep the initial style of the content block after the end of the transition). The main change is the switch to Web Animation API, which seems as performant as pure CSS animation and provides much more control. This also had eliminated all performance optimization hack from the original solution.

<script setup lang="ts">
interface Props {
  duration?: number;
  easingEnter?: string;
  easingLeave?: string;
  opacityClosed?: number;
  opacityOpened?: number;
}

const props = withDefaults(defineProps<Props>(), {
  duration: 250,
  easingEnter: "ease-in-out",
  easingLeave: "ease-in-out",
  opacityClosed: 0,
  opacityOpened: 1,
});

const closed = "0px";

interface initialStyle {
  height: string;
  width: string;
  position: string;
  visibility: string;
  overflow: string;
  paddingTop: string;
  paddingBottom: string;
  borderTopWidth: string;
  borderBottomWidth: string;
  marginTop: string;
  marginBottom: string;
}

function getElementStyle(element: HTMLElement) {
  return {
    height: element.style.height,
    width: element.style.width,
    position: element.style.position,
    visibility: element.style.visibility,
    overflow: element.style.overflow,
    paddingTop: element.style.paddingTop,
    paddingBottom: element.style.paddingBottom,
    borderTopWidth: element.style.borderTopWidth,
    borderBottomWidth: element.style.borderBottomWidth,
    marginTop: element.style.marginTop,
    marginBottom: element.style.marginBottom,
  };
}

function prepareElement(element: HTMLElement, initialStyle: initialStyle) {
  const { width } = getComputedStyle(element);
  element.style.width = width;
  element.style.position = "absolute";
  element.style.visibility = "hidden";
  element.style.height = "";
  let { height } = getComputedStyle(element);
  element.style.width = initialStyle.width;
  element.style.position = initialStyle.position;
  element.style.visibility = initialStyle.visibility;
  element.style.height = closed;
  element.style.overflow = "hidden";
  return initialStyle.height && initialStyle.height != closed
    ? initialStyle.height
    : height;
}

function animateTransition(
  element: HTMLElement,
  initialStyle: initialStyle,
  done: () => void,
  keyframes: Keyframe[] | PropertyIndexedKeyframes | null,
  options?: number | KeyframeAnimationOptions
) {
  const animation = element.animate(keyframes, options);
  // Set height to 'auto' to restore it after animation
  element.style.height = initialStyle.height;
  animation.onfinish = () => {
    element.style.overflow = initialStyle.overflow;
    done();
  };
}

function getEnterKeyframes(height: string, initialStyle: initialStyle) {
  return [
    {
      height: closed,
      opacity: props.opacityClosed,
      paddingTop: closed,
      paddingBottom: closed,
      borderTopWidth: closed,
      borderBottomWidth: closed,
      marginTop: closed,
      marginBottom: closed,
    },
    {
      height,
      opacity: props.opacityOpened,
      paddingTop: initialStyle.paddingTop,
      paddingBottom: initialStyle.paddingBottom,
      borderTopWidth: initialStyle.borderTopWidth,
      borderBottomWidth: initialStyle.borderBottomWidth,
      marginTop: initialStyle.marginTop,
      marginBottom: initialStyle.marginBottom,
    },
  ];
}

function enterTransition(element: Element, done: () => void) {
  const HTMLElement = element as HTMLElement;
  const initialStyle = getElementStyle(HTMLElement);
  const height = prepareElement(HTMLElement, initialStyle);
  const keyframes = getEnterKeyframes(height, initialStyle);
  const options = { duration: props.duration, easing: props.easingEnter };
  animateTransition(HTMLElement, initialStyle, done, keyframes, options);
}

function leaveTransition(element: Element, done: () => void) {
  const HTMLElement = element as HTMLElement;
  const initialStyle = getElementStyle(HTMLElement);
  const { height } = getComputedStyle(HTMLElement);
  HTMLElement.style.height = height;
  HTMLElement.style.overflow = "hidden";
  const keyframes = getEnterKeyframes(height, initialStyle).reverse();
  const options = { duration: props.duration, easing: props.easingLeave };
  animateTransition(HTMLElement, initialStyle, done, keyframes, options);
}
</script>

<template>
  <Transition :css="false" @enter="enterTransition" @leave="leaveTransition">
    <slot />
  </Transition>
</template>