使用Hammer JS作为转盘

Question

在使用Hammer JS 2.0.8构建自定义旋转木马时，我遇到了一些让它流畅工作的问题。经过多次尝试，我发现了一个真正有用的代码片段，当我最终完成这个模块时，我决定在这里同样分享

Answer 1

理查德·刘的This was the snippet that really helped报道。

出于某些原因，切换回Hammer 2.0.4使得pancancel/panend回调更可靠。从那时起，我能够完成我的解决方案。JSFiddle上也有一个complete demo

class Carousel {
constructor(options) {
    this.transiting = false;
    this.activeCard = 1;
    this.offset = 0;
    this.delta = 0;
    this.element = options.carousel;
    this.slides = this.element.children.length;
    this.element.style.width = `${this.slides * 100}%`;
    this.width = options.carousel.clientWidth;
    this.boundaryLeft = 0;
    this.boundaryRight = ((this.count - 1) / this.count) * this.width;
    this.outOfBounds = false;
    this.panRequiredToMove = options.container.clientWidth * 0.25;
    this.hammer = new Hammer(options.container);

    this.init();
}

init() {
    var self = this;

    function handleHammer(e) {
        switch (e.type) {
            case 'swipeleft':
            case 'swiperight':
                self.handleSwipe(e);
                break;
            case 'panleft':
            case 'panright':
            case 'panend':
            case 'pancancel':
                self.handlePan(e);
                break;
        }
    }

    this.hammer.on('swipeleft swiperight panleft panright panend pancancel', handleHammer);
    this.element.addEventListener("transitionend", function (event) {
        this.classList.remove('carousel--in-motion');
    }, false);
}

handleSwipe(e) {
    switch (e.direction) {
        case Hammer.DIRECTION_LEFT:
            this.next();
            break;
        case Hammer.DIRECTION_RIGHT:
            this.previous();
            break;
    }
    this.hammer.stop(true);
}

checkBounds() {    
    var beforeFirstCard = this.activeCard === 1 && (this.offset + this.delta) >= this.boundaryLeft;
    var afterLastCard = this.activeCard === this.slides && Math.abs(this.offset + this.delta) >= this.boundaryRight;

    if (beforeFirstCard) {
        this.outOfBounds = { recoilPosition: this.boundaryLeft };
    } else if (afterLastCard) {
        this.outOfBounds = { recoilPosition: this.boundaryRight * -1 };
    } else {
        this.outOfBounds = false;
    }
}

handlePan(e) {
    switch (e.type) {
        case 'panleft':
        case 'panright':
                this.checkBounds();
            if (this.outOfBounds) e.deltaX *= .2;
            this.transition(e.deltaX);
            break;
        case 'panend':
        case 'pancancel':
            if (this.outOfBounds) {
                this.recoil(this.outOfBounds.recoilPosition);
            } else if (Math.abs(e.deltaX) > this.panRequiredToMove) {
                e.deltaX > 0 ? this.previous() : this.next();
            } else {
                this.recoil();
            }
            break;
    }
}

next() {
    if (this.activeCard < this.slides) {
        let newPosition = this.activeCard / this.slides * this.width * -1;
        this.goToSlide(newPosition, () => {
            this.activeCard++;
        });
    }
}

previous() {
    if (this.activeCard > 1) {
        let activeCard = this.activeCard - (this.slides - 1);
        let newPosition = activeCard / this.slides * this.width * -1;
        this.goToSlide(newPosition, () => {
            this.activeCard--;
        });
    }
}

goToSlide(position, callback) {
    let self = this;
    let currentPosition = this.offset + this.delta;
    this.transiting = true;

// I used AnimatePlus for the other movement between slides
    animate({
        el: this.element,
        translateX: [`${currentPosition}px`, `${position}px`],
        duration: 300,
        easing: "easeInOutQuad",
        complete() {
            self.transiting = false;
            self.offset = position;
            self.delta = 0;
            if (callback) callback();
        }
    });
}

transition(deltaX) {
    this.delta = deltaX;
    let position = this.offset + this.delta;
    this.element.style.webkitTransform = `translateX(${position}px)`;
}

recoil(position) {      
    this.element.classList.add('carousel--in-motion');
    this.element.style.webkitTransform = `translateX(${position || this.offset}px)`;
}
}