1、tap事件实现
zepto 源码里面看关于tap的实现方法：
1 $(document).ready(function(){ 2 var now, delta, deltaX = 0, deltaY = 0, firstTouch, _isPointerType 3 4 if ('MSGesture' in window) { 5 gesture = new MSGesture() 6 gesture.target = document.body 7 } 8 9 $(document) 10 .bind('MSGestureEnd', function(e){ 11 var swipeDirectionFromVelocity = 12 e.velocityX > 1 ? 'Right' : e.velocityX < -1 ? 'Left' : e.velocityY > 1 ? 'Down' : e.velocityY < -1 ? 'Up' : null; 13 if (swipeDirectionFromVelocity) { 14 touch.el.trigger('swipe') 15 touch.el.trigger('swipe'+ swipeDirectionFromVelocity) 16 } 17 }) 18 .on('touchstart MSPointerDown pointerdown', function(e){ 19 if((_isPointerType = isPointerEventType(e, 'down')) && 20 !isPrimaryTouch(e)) return 21 firstTouch = _isPointerType ? e : e.touches[0] 22 if (e.touches && e.touches.length === 1 && touch.x2) { 23 // Clear out touch movement data if we have it sticking around 24 // This can occur if touchcancel doesn't fire due to preventDefault, etc. 25 touch.x2 = undefined 26 touch.y2 = undefined 27 } 28 now = Date.now() 29 delta = now - (touch.last || now) 30 touch.el = $('tagName' in firstTouch.target ? 31 firstTouch.target : firstTouch.target.parentNode) 32 touchTimeout && clearTimeout(touchTimeout) 33 touch.x1 = firstTouch.pageX 34 touch.y1 = firstTouch.pageY 35 if (delta > 0 && delta <= 250) touch.isDoubleTap = true 36 touch.last = now 37 longTapTimeout = setTimeout(longTap, longTapDelay) 38 // adds the current touch contact for IE gesture recognition 39 if (gesture && _isPointerType) gesture.addPointer(e.pointerId); 40 }) 41 .on('touchmove MSPointerMove pointermove', function(e){ 42 if((_isPointerType = isPointerEventType(e, 'move')) && 43 !isPrimaryTouch(e)) return 44 firstTouch = _isPointerType ? e : e.touches[0] 45 cancelLongTap() 46 touch.x2 = firstTouch.pageX 47 touch.y2 = firstTouch.pageY 48 49 deltaX += Math.abs(touch.x1 - touch.x2) 50 deltaY += Math.abs(touch.y1 - touch.y2) 51 }) 52 .on('touchend MSPointerUp pointerup', function(e){ 53 if((_isPointerType = isPointerEventType(e, 'up')) && 54 !isPrimaryTouch(e)) return 55 cancelLongTap() 56 57 // swipe 58 if ((touch.x2 && Math.abs(touch.x1 - touch.x2) > 30) || 59 (touch.y2 && Math.abs(touch.y1 - touch.y2) > 30)) 60 61 swipeTimeout = setTimeout(function() { 62 touch.el.trigger('swipe') 63 touch.el.trigger('swipe' + (swipeDirection(touch.x1, touch.x2, touch.y1, touch.y2))) 64 touch = {} 65 }, 0) 66 67 // normal tap 68 else if ('last' in touch) 69 // don't fire tap when delta position changed by more than 30 pixels, 70 // for instance when moving to a point and back to origin 71 if (deltaX < 30 && deltaY < 30) { 72 // delay by one tick so we can cancel the 'tap' event if 'scroll' fires 73 // ('tap' fires before 'scroll') 74 tapTimeout = setTimeout(function() { 75 76 // trigger universal 'tap' with the option to cancelTouch() 77 // (cancelTouch cancels processing of single vs double taps for faster 'tap' response) 78 var event = $.Event('tap') 79 event.cancelTouch = cancelAll 80 touch.el.trigger(event) 81 82 // trigger double tap immediately 83 if (touch.isDoubleTap) { 84 if (touch.el) touch.el.trigger('doubleTap') 85 touch = {} 86 } 87 88 // trigger single tap after 250ms of inactivity 89 else { 90 touchTimeout = setTimeout(function(){ 91 touchTimeout = null 92 if (touch.el) touch.el.trigger('singleTap') 93 touch = {} 94 }, 250) 95 } 96 }, 0) 97 } else { 98 touch = {} 99 } 100 deltaX = deltaY = 0 101 102 }) 103 // when the browser window loses focus, 104 // for example when a modal dialog is shown, 105 // cancel all ongoing events 106 .on('touchcancel MSPointerCancel pointercancel', cancelAll) 107 108 // scrolling the window indicates intention of the user 109 // to scroll, not tap or swipe, so cancel all ongoing events 110 $(window).on('scroll', cancelAll) 111 }) 112 113 ;['swipe', 'swipeLeft', 'swipeRight', 'swipeUp', 'swipeDown', 114 'doubleTap', 'tap', 'singleTap', 'longTap'].forEach(function(eventName){ 115 $.fn[eventName] = function(callback){ return this.on(eventName, callback) } 116 })
zepto的tap通过兼听绑定在document上的touch事件来完成tap事件的模拟的,及tap事件是冒泡到document上触发的再点击完成时的tap事件(touchstart ouchend)需要冒泡到document上才会触发，而在冒泡到document之前，用户手的接触屏幕(touchstart)和离开屏幕(touchend)是会触发click事件的,因为click事件有延迟触发(这就是为什么移动端不用click而用tap的原因)(大概是300ms,为了实现safari的双击事件的设计)，所以在执行完tap事件之后，弹出来的选择组件马上就隐藏了，此时click事件还在延迟的300ms之中，当300ms到来的时候，click到的其实不是完成而是隐藏之后的下方的元素，如果正下方的元素绑定的有click事件此时便会触发，如果没有绑定click事件的话就当没click，但是正下方的是input输入框(或者select选择框或者单选复选框)，点击默认聚焦而弹出输入键盘，这就是常出现的“点透”的情况。
下面一个例子看看点透是什么情况：
1 <!DOCTYPE html> 2 <html> 3 <head> 4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 5 <title></title> 6 <style type="text/css"> 7 input { 8 width: 200px; 9 height: 50px; 10 } 11 .layer { 12 width: 200px; 13 height: 200px; 14 position: absolute; 15 left: 0; 16 top: 0; 17 background: red; 18 opacity: .5; 19 } 20 </style> 21 </head> 22 <body> 23 <div class="layer" id="J_layer"></div> 24 <input type="text"> 25 26 <script type="text/javascript" src="/lib/zepto.js"></script> 27 <script type="text/javascript"> 28 $('#J_layer').on('tap', function () { 29 var $this = $(this); 30 $this.hide(); 31 }); 32 </script> 33 </body> 34 </html>
运行出来的情况是：
当点击“layer”处于“input”上方区域后出现：
上图可以看出，input获取到了焦点。
这就是点透现象，input获取到了click事件。
2、解决“点透”问题
2.1、引入fastclick.js，因为fastclick源码不依赖其他库所以你可以在原生的js前直接加上。https://github.com/ftlabs/fastclick
1 window.addEventListener( "load", function() { 2 FastClick.attach( document.body ); 3 }, false );
2.2、用touchend代替tap事件并阻止掉touchend的默认行为preventDefault()
1 $("#layer").on("touchend", function (event) { 2 //很多处理比如隐藏什么的 3 event.preventDefault(); 4 });
2.3、延迟一定的时间(300ms+)来处理事件
1 $("#layer").on("tap", function (event) { 2 setTimeout(function(){ 3 //程序处理 4 },320); 5 });
以上就是对zepto中tap方法的解说，请大家多多提问