一段代碼闡述一個輪播思路

一段代碼闡述一個輪播思路

不BB，直接上代碼：

1. if (direction === 'next') {
2.     this.index = nextIndex;
3.     /*若是是下一個，那就先吧下個的dom設置成none來移動位置，防止用戶看到*/
4.     nextEl.style.display = 'none';
5.     nextEl.style.webkitTransition = '';
6.     currentEl.style.display = 'block';
7.     currentEl.style.webkitTransition = '-webkit-transform ' + this.speed + 'ms ease-in-out';
8.     setTimeout(()=> {
9.         /*將下個放到指定的位置*/
10.         nextEl.style.webkitTransform = this.toward === 'horizontal' ? `translate3d(100%, 0, 0)` : `translate3d(0, 100%, 0)`;
11.         nextEl.style.display = 'block';
12.         nextEl.style.webkitTransition = '-webkit-transform ' + this.speed + 'ms ease-in-out';
13.         setTimeout(() => {
14.             /*開始輪播*/
15.             currentEl.style.webkitTransform = this.toward === 'horizontal' ? `translate3d(-100%, 0, 0)` : `translate3d(0, -100%, 0)`;
16.             nextEl.style.webkitTransform = `translate3d(0, 0, 0)`;
17.         }, 20);
18.     }, 10);
19. }

注意：以上只是主思路代碼，完整的代碼解讀完以後會貼出來供你們參考。

代碼解讀：思路是先判斷滾動方向，若是是向下一個節點那我就準備下一個節點到指定位置（僅適合界面一次展現一個輪播節點），若是直接移動到指定位置確定是不合理的，由於節點直接移動會讓用戶在瀏覽器界面看到，但是節點是確定要移動啊，思路很簡單，那我給節點穿一件隱身衣（display:none）,以後再移動到指定位置用戶不就看不到了，可是注意這裏存在一個問題，若是直接設置設置display：none以後立馬就移動位置的話會存在一個問題，移動的效果用戶仍然能看的到，這是由於非異步的JS代碼在執行的過程當中是會阻止瀏覽器的繪圖和重繪的，因此爲了繞開瀏覽器這個機制那就使用異步好了（setTimeout）,下一個節點的位置如今已經準備好了，如今若是仍是直接移動的話，又會存在一個問題下一個節點居然看不到移動，這是由於咱們在準備節點的節點的時候已經將它隱藏了，因此爲了讓用戶看到就不得不把隱身衣脫了（display:block）才行，這樣又得加一個異步（setTimeout）才能生效了，如今就能夠安心的執行當前節點和早已就緒的下一個節點了。

完整代碼以下：

下面的輪播JS部分的代碼是vue寫的，主要功能包括了垂直輪播，水平輪播，手勢輪播等幾個輪播的主要功能

export default {
    name: 'swipe',
    props: {
        /*默認是水平滾動*/
        toward: {
            type: String,
            default: 'vertical'
        },
        /*是否展現指示標誌*/
        showIndicators: {
            type: Boolean,
            default: true
        },
        /*滾動速度*/
        speed: {
            type: Number,
            default: 300
        },
        /*默認下標從哪兒開始*/
        defaultIndex: {
            type: Number,
            default: 0
        },
        /*自動滾動間隔*/
        interval: {
            type: Number,
            default: 3000
        }
    },
    data() {
        return {
            dots: [],    // 頁面標記圓點
            index: this.defaultIndex,   //當前頁面的下標
            pageEls: [],   // 全部的子輪播項集合
            timer: null, //輪播定時器對象
            noSwipe: false,  //禁止滾動
            startPosition: '',  //touch的起始位置
            currentPosition: '',  //touch的目前位置
            translatePosition: '',  //touch位移的位置
            distance: 10,    //touch的位移大於10的時候生效
        }
    },
    watch: {},
    beforeMount: function () {
    },
    mounted(){
        this.initSwipe();
        this.swipeTimeout();
        this.initTouchEvent();
    },
    computed: {
        getNum(){
            return this.pageEls.length;
        },
    },
    methods: {
        /*手動上一張*/
        prev(){
            window.clearTimeout(this.timer);
            this.swipeTimeout('prev');
        },
        /*手動下一張*/
        next(){
            window.clearTimeout(this.timer);
            this.swipeTimeout('next');
        },
        initTouchEvent(){
            let dom = this.$el.querySelector('.swipe-warp');
            dom.addEventListener('touchstart', this.handleTouchStart);
            dom.addEventListener('touchmove', this.handleTouchMove);
            dom.addEventListener('touchend', this.handleTouchEnd);
            console.log(dom);
        },
        /*初始化輪播節點*/
        initSwipe(){
            var children = this.$children;
            if (children.length === 1) {
                this.noSwipe = false;
                return;
            }
            children.forEach((child, _index)=> {
                this.pageEls.push(child.$el);
            });
        },
        /*定時輪播*/
        swipeTimeout(toward = 'next'){
            this.translate(toward, ()=> {
                this.timer = window.setTimeout(()=> {
                    this.swipeTimeout('next');
                }, this.interval);
            });
        },
        /*滾動方法*/
        translate(direction = 'next', cb){
            let length = this.pageEls.length;
            let currentIndex = this.index;
            let currentEl = this.pageEls[currentIndex];
            let nextIndex = ((this.index + 1) > (length - 1)) ? 0 : (this.index + 1);
            let nextEl = this.pageEls[nextIndex];
            let pervIndex = (this.index - 1) < 0 ? (length - 1) : (this.index - 1);
            let pervEl = this.pageEls[pervIndex];
            if (direction === 'next') {
                this.index = nextIndex;
                /*若是是下一個，那就先吧下個的dom設置成none來移動位置，防止用戶看到*/
                nextEl.style.display = 'none';
                nextEl.style.webkitTransition = '';
                currentEl.style.display = 'block';
                currentEl.style.webkitTransition = '-webkit-transform ' + this.speed + 'ms ease-in-out';
                setTimeout(()=> {
                    /*將下個放到指定的位置*/
                    nextEl.style.webkitTransform = this.toward === 'horizontal' ? `translate3d(100%, 0, 0)` : `translate3d(0, 100%, 0)`;
                    nextEl.style.display = 'block';
                    nextEl.style.webkitTransition = '-webkit-transform ' + this.speed + 'ms ease-in-out';
                    setTimeout(() => {
                        /*開始輪播*/
                        currentEl.style.webkitTransform = this.toward === 'horizontal' ? `translate3d(-100%, 0, 0)` : `translate3d(0, -100%, 0)`;
                        nextEl.style.webkitTransform = `translate3d(0, 0, 0)`;
                    }, 20);
                }, 10);
            } else {
                this.index = pervIndex;
                /*若是是上一個，那就先吧上個的dom設置成none來移動位置，防止用戶看到*/
                pervEl.style.display = 'none';
                pervEl.style.webkitTransition = '';
                currentEl.style.display = 'block';
                currentEl.style.webkitTransition = '-webkit-transform ' + this.speed + 'ms ease-in-out';
                setTimeout(()=> {
                    /*將上個放到指定的位置*/
                    pervEl.style.webkitTransform = this.toward === 'horizontal' ? `translate3d(-100%, 0, 0)` : `translate3d(0, -100%, 0)`;
                    pervEl.style.display = 'block';
                    pervEl.style.webkitTransition = '-webkit-transform ' + this.speed + 'ms ease-in-out';
                    setTimeout(() => {
                        /*開始輪播*/
                        currentEl.style.webkitTransform = this.toward === 'horizontal' ? `translate3d(100%, 0, 0)` : `translate3d(0, 100%, 0)`;
                        pervEl.style.webkitTransform = `translate3d(0, 0, 0)`;
                    }, 20);
                }, 10);
            }
            this.once(currentEl, 'webkitTransitionEnd', ()=> {
                cb && cb();
            });
        },
        handleTouchStart($evnet){
            this.startPosition = this.toward === 'horizontal' ? $evnet.touches[0].clientX : $evnet.touches[0].clientY;
        },
        handleTouchMove($evnet){
            this.currentPosition = this.toward === 'horizontal' ? $evnet.touches[0].clientX : $evnet.touches[0].clientY;
            this.translatePosition = this.currentPosition - this.startPosition;
            this.translatePosition !== 0 && window.clearTimeout(this.timer);
            $evnet.preventDefault();
            $evnet.stopPropagation();
        },
        handleTouchEnd($evnet){
            this.translatePosition < 0 && this.translatePosition < -this.distance && this.swipeTimeout('next');
            this.translatePosition > 0 && this.translatePosition > this.distance && this.swipeTimeout('prev');
        },
        /*管理事件*/
        once(el, event, fn) {
            var that = this;
            var listener = function () {
                if (fn) {
                    fn.apply(this, arguments);
                }
                that.off(el, event, listener);
            };
            this.on(el, event, listener);
        },
        /*監聽事件*/
        on(element, event, handler){
            if (element && event && handler) {
                element.addEventListener(event, handler, false);
            }
        },
        /*移除事件*/
        off(element, event, handler) {
            if (element && event) {
                element.removeEventListener(event, handler, false);
            }
        }
    }
};