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Animations

Overview​

Ionic Animations is a tool that enables developers to create complex animations in a platform-agnostic manner, without requiring a specific framework or an Ionic app.

Creating efficient animations can be challenging, as it is limited by the available libraries and hardware resources of the device. Moreover, many animation libraries use a JavaScript-driven approach, which can reduce the scalability of animations and use up CPU time.

Ionic Animations, on the other hand, uses the Web Animations API, which offloads all the computation and running of animations to the browser. This approach allows the browser to optimize the animations and ensure their smooth execution. In cases where Web Animations are not supported, Ionic Animations will fall back to CSS Animations, which should have a negligible difference in performance.

Installation​

Developers using Ionic Core and JavaScript should install the latest version of @ionic/core.

import { createAnimation } from 'https://cdn.jsdelivr.net/npm/@ionic/core@latest/dist/esm/index.mjs';

...

const animation = createAnimation()
  .addElement(myElementRef)
  .duration(1000)
  .fromTo('opacity', '1', '0.5');
}

Basic Animations​

Usage​

createAnimation()
  .addElement(document.querySelector('.square'))
  .duration(1500)
  .iterations(Infinity)
  .fromTo('transform', 'translateX(0px)', 'translateX(100px)')
  .fromTo('opacity', '1', '0.2');

In the example above, an animation that changes the opacity on the .square element and moves it from left to right along the X axis has been created. This animation will run an infinite number of times, and each iteration of the animation will last 1500ms.

By default, all Ionic Animations are paused until the play method is called.

Keyframe Animations​

Ionic Animations allows you to control the intermediate steps in an animation using keyframes. Any valid CSS property can be used here, and you can even use CSS Variables as values.

Hyphenated CSS properties should be written using camel case when writing keyframes. For example, border-radius should be written as borderRadius. This also applies to the fromTo(), from(), and to() methods.

Usage​

createAnimation()
  .addElement(document.querySelector('.square'))
  .duration(3000)
  .iterations(Infinity)
  .keyframes([
    { offset: 0, background: 'red' },
    { offset: 0.72, background: 'var(--background)' },
    { offset: 1, background: 'green' }
  ]);

In the example above, the .square element will transition from a red background color, to a background color defined by the --background variable, and then transition on to a green background color.

Each keyframe object contains an offset property. offset is a value between 0 and 1 that defines the keyframe step. Offset values must go in ascending order and cannot repeat.

Grouped Animations​

Multiple elements can be animated at the same time and controlled via a single parent animation object. Child animations inherit properties such as duration, easing, and iterations unless otherwise specified. A parent animation's onFinish callback will not be called until all child animations have completed.

Usage​

const squareA = createAnimation()
  .addElement(document.querySelector('.square-a'))
  .keyframes([
    { offset: 0, transform: 'scale(1) rotate(0)' },
    { offset: 0.5, transform: 'scale(1.2) rotate(45deg)' },
    { offset: 1, transform: 'scale(1) rotate(45deg)' }
  ]);

const squareB = createAnimation()
  .addElement(document.querySelector('.square-b'))
  .keyframes([
    { offset: 0, transform: 'scale(1))', opacity: '1' },
    { offset: 0.5, transform: 'scale(1.2)', opacity: '0.3' },
    { offset: 1, transform: 'scale(1)', opacity: '1' }
  ]);

const squareC = createAnimation()
  .addElement(document.querySelector('.square-c'))
  .duration(5000)
  .keyframes([
    { offset: 0, transform: 'scale(1))', opacity: '0.5' },
    { offset: 0.5, transform: 'scale(0.8)', opacity: '1' },
    { offset: 1, transform: 'scale(1)', opacity: '0.5' }
  ]);

const parent = createAnimation()
  .duration(2000)
  .iterations(Infinity)
  .addAnimation([squareA, squareB, squareC]);

This example shows 3 child animations controlled by a single parent animation. Animations squareA and squareB inherit the parent animation's duration of 2000ms, but animation squareC has a duration of 5000ms since it was explicitly set.

Before and After Hooks​

Ionic Animations provides hooks that let you alter an element before an animation runs and after an animation completes. These hooks can be used to perform DOM reads and writes as well as add or remove classes and inline styles.

Usage​

createAnimation()
  .addElement(document.querySelector('.square'))
  .duration(2000)
  .beforeStyles({
    opacity: 0.2
  })
  .afterStyles({
    background: 'rgba(0, 255, 0, 0.5)'
  })
  .afterClearStyles(['opacity'])
  .keyframes([
    { offset: 0, transform: 'scale(1)' },
    { offset: 0.5, transform: 'scale(1.5)' },
    { offset: 1, transform: 'scale(1)' }
  ])

In this example, an inline opacity of 0.2 is set on the .square element prior to the animation starting. Once the animation finishes, the background color of the element is set to rgba(0, 255, 0, 0.5), and the inline opacity is cleared.

See Methods for a complete list of hooks.

Chained Animations​

Animations can be chained to run one after the other. The play method returns a Promise that resolves when the animation has completed.

Usage​

const squareA = createAnimation()
  .addElement(document.querySelector('.square-a'))
  .fill('none')
  .duration(1000)
  .keyframes([
    { offset: 0, transform: 'scale(1) rotate(0)' },
    { offset: 0.5, transform: 'scale(1.2) rotate(45deg)' },
    { offset: 1, transform: 'scale(1) rotate(0)' }
  ]);

const squareB = createAnimation()
  .addElement(document.querySelector('.square-b'))
  .fill('none')
  .duration(1000)
  .keyframes([
    { offset: 0, transform: 'scale(1)', opacity: '1' },
    { offset: 0.5, transform: 'scale(1.2)', opacity: '0.3' },
    { offset: 1, transform: 'scale(1)', opacity: '1' }
  ]);

const squareC = createAnimation()
  .addElement(document.querySelector('.square-c'))
  .fill('none')
  .duration(1000)
  .keyframes([
    { offset: 0, transform: 'scale(1)', opacity: '0.5' },
    { offset: 0.5, transform: 'scale(0.8)', opacity: '1' },
    { offset: 1, transform: 'scale(1)', opacity: '0.5' }
  ]);

await squareA.play();
await squareB.play();
await squareC.play();

Gesture Animations​

Ionic Animations gives developers the ability to create powerful gesture-based animations by integrating seamlessly with Ionic Gestures.

Usage​

let initialStep = 0;
let started = false;

const square = document.querySelector('.square');
const MAX_TRANSLATE = 400;

const animation = createAnimation()
  .addElement(square)
  .duration(1000)
  .fromTo('transform', 'translateX(0)', `translateX(${MAX_TRANSLATE}px)`);

const gesture = createGesture({
  el: square,
  threshold: 0,
  gestureName: 'square-drag',
  onMove: ev => onMove(ev),
  onEnd: ev => onEnd(ev)
})

gesture.enable(true);

const onMove = (ev): {
  if (!started) {
    animation.progressStart();
    started = true;
  }

  animation.progressStep(getStep(ev));
}

const onEnd = (ev): {
  if (!started) { return; }

  gesture.enable(false);

  const step = getStep(ev);
  const shouldComplete = step > 0.5;

  animation
    .progressEnd((shouldComplete) ? 1 : 0, step)
    .onFinish((): { gesture.enable(true); });

  initialStep = (shouldComplete) ? MAX_TRANSLATE : 0;
  started = false;
}

const clamp = (min, n, max): {
  return Math.max(min, Math.min(n, max));
};

const getStep = (ev): {
  const delta = initialStep + ev.deltaX;
  return clamp(0, delta / MAX_TRANSLATE, 1);
}

In this example we are creating a track along which we can drag the .square element. Our animation object will take care of moving the .square element either left or right, and our gesture object will instruct the animation object which direction to move in.

Preference-Based Animations​

Developers can also tailor their animations to user preferences such as prefers-reduced-motion and prefers-color-scheme using CSS Variables.

Usage​

.square {
  width: 100px;
  height: 100px;
  opacity: 0.5;
  background: blue;
  margin: 10px;

  --background: red;
}

@media (prefers-color-scheme: dark) {
  .square {
    --background: green;
  }
}
createAnimation()
   .addElement(document.querySelector('.square'))
   .duration(1500)
   .iterations(Infinity)
   .direction('alternate')
   .fromTo('background', 'blue', 'var(--background)');

This method works in all supported browsers when creating animations for the first time. Most browsers are also capable of dynamically updating keyframe animations as the CSS Variables change.

Safari does not currently support dynamically updating keyframe animations. For developers who need this kind of support in Safari, they can use MediaQueryList.addListener().

Overriding Ionic Component Animations​

Certain Ionic components allow developers to provide custom animations. All animations are provided as either properties on the component or are set via a global config.

Modals​

customElements.define('modal-page', class extends HTMLElement {
  connectedCallback() {
    this.innerHTML = `
      <ion-header>
        <ion-toolbar>
          <ion-title>Modal Header</ion-title>
        </ion-toolbar>
      </ion-header>
      <ion-content class="ion-padding">
        Modal Content
      </ion-content>
    `;
  }
});

function presentModal() {
  const enterAnimation = (baseEl: any) => {
    const root = baseEl.shadowRoot;

    const backdropAnimation = createAnimation()
      .addElement(root.querySelector('ion-backdrop')!)
      .fromTo('opacity', '0.01', 'var(--backdrop-opacity)');

    const wrapperAnimation = createAnimation()
      .addElement(root.querySelector('.modal-wrapper')!)
      .keyframes([
        { offset: 0, opacity: '0', transform: 'scale(0)' },
        { offset: 1, opacity: '0.99', transform: 'scale(1)' }
      ]);

    return createAnimation()
      .addElement(baseEl)
      .easing('ease-out')
      .duration(500)
      .addAnimation([backdropAnimation, wrapperAnimation]);
  }

  const leaveAnimation = (baseEl: any) => {
    return enterAnimation(baseEl).direction('reverse');
  }

  // create the modal with the `modal-page` component
  const modalElement = document.createElement('ion-modal');
  modalElement.component = 'modal-page';
  modalElement.enterAnimation = enterAnimation;
  modalElement.leaveAnimation = leaveAnimation;

  // present the modal
  document.body.appendChild(modalElement);
  return modalElement.present();
}

Performance Considerations​

CSS and Web Animations are usually handled on the compositor thread. This is different than the main thread where layout, painting, styling, and your JavaScript is executed. It is recommended that you prefer using properties that can be handled on the compositor thread for optimal animation performance.

Animating properties such as height and width cause additional layouts and paints which can cause jank and degrade animation performance. On the other hand, animating properties such as transform and opacity are highly optimizable by the browser and typically do not cause much jank.

For information on which CSS properties cause layouts or paints to occur, see CSS Triggers.

Debugging​

For debugging animations in Chrome, there is a great blog post about inspecting animations using the Chrome DevTools: https://developers.google.com/web/tools/chrome-devtools/inspect-styles/animations.

It is also recommended to assign unique identifiers to your animations. These identifiers will show up in the Animations inspector in Chrome and should make it easier to debug:

/**
 * The animation for the .square element should
 * show "my-animation-identifier" in Chrome DevTools.
 */
const animation = createAnimation('my-animation-identifier')
  .addElement(document.querySelector('.square'))
  .duration(1000)
  .fromTo('opacity', '1', '0');

API​

This section provides a list of all the methods and properties available on the Animation class.

Interfaces​

AnimationDirection​

type AnimationDirection = 'normal' | 'reverse' | 'alternate' | 'alternate-reverse';

AnimationFill​

type AnimationFill = 'auto' | 'none' | 'forwards' | 'backwards' | 'both';

AnimationBuilder​

type AnimationBuilder = (baseEl: any, opts?: any) => Animation;
注記

opts are additional options that are specific to the custom animation. For example, the sheet modal enter animation includes information for the current breakpoint.

AnimationCallbackOptions​

interface AnimationCallbackOptions {
  /**
   * If true, the associated callback will only be fired once.
   */
  oneTimeCallback: boolean;
}

AnimationPlayOptions​

interface AnimationPlayOptions {
  /**
   * If true, the animation will play synchronously.
   * This is the equivalent of running the animation
   * with a duration of 0ms.
   */
  sync: boolean;
}

Properties​

NameDescription
childAnimations: Animation[]All child animations of a given parent animation.
elements: HTMLElement[]All elements attached to an animation.
parentAnimation?: AnimationThe parent animation of a given animation object.

Methods​

NameDescription
addAnimation(animationToAdd: Animation | Animation[]): AnimationGroup one or more animations together to be controlled by a parent animation.
addElement(el: Element | Element[] | Node | Node[] | NodeList): AnimationAdd one or more elements to the animation.
afterAddClass(className: string | string[]): AnimationAdd a class or array of classes to be added to all elements in an animation after the animation ends.
afterAddRead(readFn: (): void): AnimationAdd a function that performs a DOM read to be run after the animation ends.
afterAddWrite(writeFn: (): void): AnimationAdd a function that performs a DOM write to be run after the animation ends.
afterClearStyles(propertyNames: string[]): AnimationAdd an array of property names to be cleared from the inline styles on all elements in an animation after the animation ends.
afterRemoveClass(className: string | string[]): AnimationAdd a class or an array of classes to be removed from all elements in an animation after the animation ends.
afterStyles(styles: { [property: string]: any }): AnimationAdd an object of styles to be applied to all elements in an animation after the animation ends.
beforeAddClass(className: string | string[]): AnimationAdd a class or array of classes to be added to all elements in an animation before the animation starts.
beforeAddRead(readFn: (): void): AnimationAdd a function that performs a DOM read to be run before the animation starts.
beforeAddWrite(writeFn: (): void): AnimationAdd a function that performs a DOM write to be run before the animation starts.
beforeClearStyles(propertyNames: string[]): AnimationAdd an array of property names to be cleared from the inline styles on all elements in an animation before the animation starts.
beforeRemoveClass(className: string | string[]): AnimationAdd a class or an array of classes to be removed from all elements in an animation before the animation starts.
beforeStyles(styles: { [property: string]: any }): AnimationAdd an object of styles to be applied to all elements in an animation before the animation starts.
direction(direction?: AnimationDirection): AnimationSet the direction the animation should play in.
delay(delay?: number): AnimationSet the delay for the start of the animation in milliseconds.
destroy(clearStyleSheets?: boolean): AnimationDestroy the animation and clear all elements, child animations, and keyframes.
duration(duration?: number): AnimationSet the duration of the animation in milliseconds.
easing(easing?: string): AnimationSet the easing of the animation in milliseconds. See Easing Effects for a list of accepted easing values.
from(property: string, value: any): AnimationSet the start styles of the animation.
fromTo(property: string, fromValue: any, toValue: any): AnimationSet the start and end styles of the animation.
fill(fill?: AnimationFill): AnimationSet how the animation applies styles to its elements before and after the animation's execution.
iterations(iterations: number): AnimationSet the number of times the animation cycle should be played before stopping.
keyframes(keyframes: any[]): AnimationSet the keyframes for an animation.
onFinish(callback: (didComplete: boolean, animation: Animation): void, opts?: AnimationCallbackOptions): AnimationAdd a callback to be run upon the animation ending.
pause(): AnimationPause the animation.
play(opts?: AnimationPlayOptions): Promise<void>Play the animation.
progressEnd(playTo?: 0 | 1, step: number, dur?: number): AnimationStop seeking through an animation.
progressStart(forceLinearEasing?: boolean, step?: number): AnimationBegin seeking through an animation.
progressStep(step: number): AnimationSeek through an animation.
stop(): AnimationStop the animation and reset all elements to their initial state.
to(property: string, value: any): AnimationSet the end styles of the animation.

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