HTML5單頁(yè)面手勢(shì)滑屏切換原理分析

<div id="viewport" class="viewport">
    <div class="pageview" style="background: #3b76c0" >
        <h3 >頁(yè)面-1</h3>
    </div>
    <div class="pageview" style="background: #58c03b;">
        <h3>頁(yè)面-2</h3>
    </div>
    <div class="pageview" style="background: #c03b25;">
        <h3>頁(yè)面-3</h3>
    </div>
    <div class="pageview" style="background: #e0a718;">
        <h3>頁(yè)面-4</h3>
    </div>
    <div class="pageview" style="background: #c03eac;">
        <h3>頁(yè)面-5</h3>
    </div>
</div>

.viewport{
   width: 500%;
   height: 100%;
   display: -webkit-box;
   overflow: hidden;
   //pointer-events: none; //這句話會(huì)導(dǎo)致整個(gè)頁(yè)面上的點(diǎn)擊事件失效，如需綁定點(diǎn)擊事件，請(qǐng)注掉
   -webkit-transform: translate3d(0,0,0);
   backface-visibility: hidden;
   position: relative;
}

/*手指放在屏幕上*/
document.addEventListener("touchstart",function(e){
   e.preventDefault();
   var touch = e.touches[0];
   startX = touch.pageX;
   startY = touch.pageY;
   initialPos = currentPosition;   //本次滑動(dòng)前的初始位置
   viewport.style.webkitTransition = ""; //取消動(dòng)畫(huà)結(jié)果
   startT = new Date().getTime(); //記錄手指按下的開(kāi)始時(shí)間
   isMove = false; //是否產(chǎn)生滑動(dòng)
}.bind(this),false);

/*手指在屏幕上滑動(dòng)，頁(yè)面追隨手指移動(dòng)*/
document.addEventListener("touchmove",function(e){
   e.preventDefault();
   var touch = e.touches[0];
   var deltaX = touch.pageX - startX;
   var deltaY = touch.pageY - startY;
   //假如X方向上的位移大于Y方向，則認(rèn)為是左右滑動(dòng)
   if (Math.abs(deltaX) > Math.abs(deltaY)){
       moveLength = deltaX;
       var translate = initialPos + deltaX; //當(dāng)前必要移動(dòng)到的位置
       //假如translate>0 或 < maxWidth,則透露表現(xiàn)頁(yè)面超出邊界
       if (translate <=0 && translate >= maxWidth){
           //移動(dòng)頁(yè)面
           this.transform.call(viewport,translate);
           isMove = true;
       }
       direction = deltaX>0?"right":"left"; //判斷手指滑動(dòng)的方向
   }
}.bind(this),false);

/*手指脫離屏幕時(shí)，計(jì)算最終必要停頓在哪一頁(yè)*/
document.addEventListener("touchend",function(e){
   e.preventDefault();
   var translate = 0;
   //計(jì)算手指在屏幕上停頓的時(shí)間
   var deltaT = new Date().getTime() - startT;
   if (isMove){ //發(fā)生了左右滑動(dòng)
        //使用動(dòng)畫(huà)過(guò)渡讓頁(yè)面滑動(dòng)到最終的位置
        viewport.style.webkitTransition = "0.3s ease -webkit-transform";
        if(deltaT < 300){ //假如停頓時(shí)間小于300ms,則認(rèn)為是快速滑動(dòng)，無(wú)論滑動(dòng)距離是多少，都停頓到下一頁(yè)
            translate = direction == 'left'?
            currentPosition-(pageWidth+moveLength):currentPosition+pageWidth-moveLength;
            //假如最終位置超過(guò)邊界位置，則停頓在邊界位置
            translate = translate > 0 ? 0 : translate; //左邊界
            translate = translate < maxWidth ? maxWidth : translate; //右邊界
        }else {
            //假如滑動(dòng)距離小于屏幕的50%，則退回到上一頁(yè)
            if (Math.abs(moveLength)/pageWidth < 0.5){
                translate = currentPosition-moveLength;
            }else{
                //假如滑動(dòng)距離大于屏幕的50%，則滑動(dòng)到下一頁(yè)
                translate = direction == 'left'?
                currentPosition-(pageWidth+moveLength):currentPosition+pageWidth-moveLength;
                translate = translate > 0 ? 0 : translate;
                translate = translate < maxWidth ? maxWidth : translate;
            }
        }
        //實(shí)行滑動(dòng)，讓頁(yè)面完備的表現(xiàn)到屏幕上
        this.transform.call(viewport,translate);
    }
}.bind(this),false);

//計(jì)算當(dāng)前的頁(yè)碼
pageNow = Math.round(Math.abs(translate) / pageWidth) + 1;
 
setTimeout(function(){
    //設(shè)置頁(yè)碼，DOM操作必要放到子線程中，否則會(huì)出現(xiàn)卡頓
    this.setPageNow();
}.bind(this),100);