How do I implement element / shuffle reordering animation using Angular ngFor?
Vue users can easily implement element play animations like this, see their official docs:
I search a lot but cannot find a solution for Angular users. ngFor
seems to toggle the content of the element instead of moving the elements when shuffling.
Here's my demo: http://embed.plnkr.co/3IcKcC/
When you press Shift, you will see the animation of moving elements thanks to li {transform: all 1s;}
. But when you shuffle them, there is no animation. So I'm here to ask for a solution.
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2 answers
Here is a simple implementation of such functionality Plunker Example
1) Build directives
@Directive({
selector: '[transition-group-item]'
})
export class TransitionGroupItemDirective {
prevPos: any;
newPos: any;
el: HTMLElement;
moved: boolean;
moveCallback: any;
constructor(elRef: ElementRef) {
this.el = elRef.nativeElement;
}
}
@Component({
selector: '[transition-group]',
template: '<ng-content></ng-content>'
})
export class TransitionGroupComponent {
@Input('transition-group') class;
@ContentChildren(TransitionGroupItemDirective) items: QueryList<TransitionGroupItemDirective>;
ngAfterContentInit() {
this.refreshPosition('prevPos');
this.items.changes.subscribe(items => {
items.forEach(item => {
item.prevPos = item.newPos || item.prevPos;
});
items.forEach(this.runCallback);
this.refreshPosition('newPos');
items.forEach(this.applyTranslation);
// force reflow to put everything in position
const offSet = document.body.offsetHeight;
this.items.forEach(this.runTransition.bind(this));
})
}
runCallback(item: TransitionGroupItemDirective) {
if(item.moveCallback) {
item.moveCallback();
}
}
runTransition(item: TransitionGroupItemDirective) {
if (!item.moved) {
return;
}
const cssClass = this.class + '-move';
let el = item.el;
let style: any = el.style;
el.classList.add(cssClass);
style.transform = style.WebkitTransform = style.transitionDuration = '';
el.addEventListener('transitionend', item.moveCallback = (e: any) => {
if (!e || /transform$/.test(e.propertyName)) {
el.removeEventListener('transitionend', item.moveCallback);
item.moveCallback = null;
el.classList.remove(cssClass);
}
});
}
refreshPosition(prop: string) {
this.items.forEach(item => {
item[prop] = item.el.getBoundingClientRect();
});
}
applyTranslation(item: TransitionGroupItemDirective) {
item.moved = false;
const dx = item.prevPos.left - item.newPos.left;
const dy = item.prevPos.top - item.newPos.top;
if (dx || dy) {
item.moved = true;
let style: any = item.el.style;
style.transform = style.WebkitTransform = 'translate(' + dx + 'px,' + dy + 'px)';
style.transitionDuration = '0s';
}
}
}
2) Use it like this
<ul [transition-group]="'flip-list'">
<li *ngFor="let item of items" transition-group-item>
{{ item }}
</li>
</ul>
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Here is my version of @yurzui's code. Changes:
- supports insertion and deletion of elements.
- forced reload keeps web package optimizations
import { Component, ContentChildren, Directive, ElementRef, Input, QueryList } from '@angular/core';
@Directive({
selector: '[transition-group-item]'
})
export class TransitionGroupItemDirective {
prevPos: any;
newPos: any;
el: HTMLElement;
moved: boolean;
moveCallback: any;
constructor(elRef: ElementRef) {
this.el = elRef.nativeElement;
}
}
@Component({
selector: '[transition-group]',
template: '<ng-content></ng-content>'
})
export class TransitionGroupComponent {
@Input('transition-group') class;
@ContentChildren(TransitionGroupItemDirective) items: QueryList<TransitionGroupItemDirective>;
ngAfterViewInit() {
setTimeout(() => this.refreshPosition('prevPos'), 0); // save init positions on next 'tick'
this.items.changes.subscribe(items => {
items.forEach(item => item.prevPos = item.newPos || item.prevPos);
items.forEach(this.runCallback);
this.refreshPosition('newPos');
items.forEach(item => item.prevPos = item.prevPos || item.newPos); // for new items
const animate = () => {
items.forEach(this.applyTranslation);
this['_forceReflow'] = document.body.offsetHeight; // force reflow to put everything in position
this.items.forEach(this.runTransition.bind(this));
}
const willMoveSome = items.some((item) => {
const dx = item.prevPos.left - item.newPos.left;
const dy = item.prevPos.top - item.newPos.top;
return dx || dy;
});
if (willMoveSome) {
animate();
} else {
setTimeout(() => { // for removed items
this.refreshPosition('newPos');
animate();
}, 0);
}
})
}
runCallback(item: TransitionGroupItemDirective) {
if (item.moveCallback) {
item.moveCallback();
}
}
runTransition(item: TransitionGroupItemDirective) {
if (!item.moved) {
return;
}
const cssClass = this.class + '-move';
let el = item.el;
let style: any = el.style;
el.classList.add(cssClass);
style.transform = style.WebkitTransform = style.transitionDuration = '';
el.addEventListener('transitionend', item.moveCallback = (e: any) => {
if (!e || /transform$/.test(e.propertyName)) {
el.removeEventListener('transitionend', item.moveCallback);
item.moveCallback = null;
el.classList.remove(cssClass);
}
});
}
refreshPosition(prop: string) {
this.items.forEach(item => {
item[prop] = item.el.getBoundingClientRect();
});
}
applyTranslation(item: TransitionGroupItemDirective) {
item.moved = false;
const dx = item.prevPos.left - item.newPos.left;
const dy = item.prevPos.top - item.newPos.top;
if (dx || dy) {
item.moved = true;
let style: any = item.el.style;
style.transform = style.WebkitTransform = 'translate(' + dx + 'px,' + dy + 'px)';
style.transitionDuration = '0s';
}
}
}
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