1、 touch库实现了什么和引入背景

click事件在移动端上会有 300ms 的延迟，同时因为需要 长按 ， 双触击 等富交互，所以我们通常都会引入类似 zepto 这样的库。zepto 中touch库实现了 ‘swipe‘, ‘swipeLeft‘, ‘swipeRight‘, ‘swipeUp‘, ‘swipeDown‘, ‘doubleTap‘, ‘tap‘, ‘singleTap‘, ‘longTap‘ 这样一些功能。

2、touch库实现‘swipe‘, ‘swipeLeft‘, ‘swipeRight‘, ‘swipeUp‘, ‘swipeDown‘, ‘doubleTap‘, ‘tap‘, ‘singleTap‘, ‘longTap‘重要源代码（绑定在touchend事件上）

处理Touch事件能让你了解到用户的每一根手指的位置，在touch事件触发的时候产生，可以通过touch event handler的event对象取到，如果基于zepto.js开发，一般是通过event.touches[0]来获取属性。

重要属性

• clientX、clientY：触摸点相对于浏览器窗口viewport的位置
• pageX、pageY： 触摸点相对于页面的位置
• screenX,screenY：触摸点相对于屏幕的位置
• identifier:touch：对象的unique ID

你可以绑定以下四种Touch事件来了解基本的touch事件：

• touchstart:手指触摸屏幕上的时候触发
• touchmove:手指在屏幕上移动的时候触发
• touchend:手指从屏幕上拿起的时候触发
• touchcancel:系统取消touch事件的时候触发

Touch模块添加以下事件，可以使用 on 和 off 来绑定。

• tap —元素tap的时候触发。
• singleTap and doubleTap — 这一对事件可以用来检测元素上的单击和双击。(如果你不需要检测单击、双击，使用 tap 代替)。
• longTap — 当一个元素被按住超过750ms触发。
• swipe, swipeLeft, swipeRight, swipeUp, swipeDown — 当元素被划过时触发。(可选择给定的方向)

这些事件也是所有Zepto对象集合上的快捷方法。

操作说明

当你触摸屏幕并抬起手指，只触发touchstart和touched，当如果手指触摸屏幕并移动后抬起会触发touchstart，多次touchmove,touchend或touchcanel，可以根据基本的touch事件来封装成你想要实现复杂的效果，比如向左或向右滑动，向上或向下滑动，并在滑动时封装你想实现的效果。

touch.js封装好了滑动事件的处理，将其添加到自己的项目中，就可以直接调用向右、右、上、下滑动的事件。这样zepto.js官网手册中的例子就可以正常运行了。

使用示例

<style>.delete { display: none; }</style>
<ul id=items>
  <li>List item 1 <span class=delete>DELETE</span></li>
  <li>List item 2 <span class=delete>DELETE</span></li>
</ul>

<script>
// show delete buttons on swipe
$(‘#items li‘).swipe(function(){
  $(‘.delete‘).hide()
  $(‘.delete‘, this).show()
})
// delete row on tapping delete button
$(‘.delete‘).tap(function(){
  $(this).parent(‘li‘).remove()
})
</script>
官网下载下来的zepto.js在后面新增下面代码

;
(function($) {
var touch = {},
touchTimeout, tapTimeout, swipeTimeout, longTapTimeout,
longTapDelay = 750,
gesture
function swipeDirection(x1, x2, y1, y2) {
return Math.abs(x1 - x2) >=
Math.abs(y1 - y2) ? (x1 - x2 > 0 ? ‘Left‘ : ‘Right‘) : (y1 - y2 > 0 ? ‘Up‘ : ‘Down‘)
}
function longTap() {
longTapTimeout = null
if (touch.last) {
touch.el.trigger(‘longTap‘)
touch = {}
}
}
function cancelLongTap() {
if (longTapTimeout) clearTimeout(longTapTimeout)
longTapTimeout = null
}
function cancelAll() {
if (touchTimeout) clearTimeout(touchTimeout)
if (tapTimeout) clearTimeout(tapTimeout)
if (swipeTimeout) clearTimeout(swipeTimeout)
if (longTapTimeout) clearTimeout(longTapTimeout)
touchTimeout = tapTimeout = swipeTimeout = longTapTimeout = null
touch = {}
}
function isPrimaryTouch(event) {
return (event.pointerType == ‘touch‘ ||
event.pointerType == event.MSPOINTER_TYPE_TOUCH) && event.isPrimary
}
function isPointerEventType(e, type) {
return (e.type == ‘pointer‘ + type ||
e.type.toLowerCase() == ‘mspointer‘ + type)
}
$(document).ready(function() {
var now, delta, deltaX = 0,
deltaY = 0,
firstTouch, _isPointerType
if (‘MSGesture‘ in window) {
gesture = new MSGesture()
gesture.target = document.body
}
$(document)
.bind(‘MSGestureEnd‘, function(e) {
var swipeDirectionFromVelocity =
e.velocityX > 1 ? ‘Right‘ : e.velocityX < -1 ? ‘Left‘ : e.velocityY > 1 ? ‘Down‘ : e.velocityY < -1 ? ‘Up‘ : null;
if (swipeDirectionFromVelocity) {
touch.el.trigger(‘swipe‘)
touch.el.trigger(‘swipe‘ + swipeDirectionFromVelocity)
}
})
.on(‘touchstart MSPointerDown pointerdown‘, function(e) {
if ((_isPointerType = isPointerEventType(e, ‘down‘)) && !isPrimaryTouch(e)) return
firstTouch = _isPointerType ? e : e.touches[0]
if (e.touches && e.touches.length === 1 && touch.x2) {
// Clear out touch movement data if we have it sticking around
// This can occur if touchcancel doesn‘t fire due to preventDefault, etc.
touch.x2 = undefined
touch.y2 = undefined
}
now = Date.now()
delta = now - (touch.last || now)
touch.el = $(‘tagName‘ in firstTouch.target ? firstTouch.target : firstTouch.target.parentNode)
touchTimeout && clearTimeout(touchTimeout)
touch.x1 = firstTouch.pageX
touch.y1 = firstTouch.pageY
if (delta > 0 && delta <= 250) touch.isDoubleTap = true
touch.last = now
longTapTimeout = setTimeout(longTap, longTapDelay)
// adds the current touch contact for IE gesture recognition
if (gesture && _isPointerType) gesture.addPointer(e.pointerId);
})
.on(‘touchmove MSPointerMove pointermove‘, function(e) {
if ((_isPointerType = isPointerEventType(e, ‘move‘)) && !isPrimaryTouch(e)) return
firstTouch = _isPointerType ? e : e.touches[0]
cancelLongTap()
touch.x2 = firstTouch.pageX
touch.y2 = firstTouch.pageY
deltaX += Math.abs(touch.x1 - touch.x2)
deltaY += Math.abs(touch.y1 - touch.y2)
})
.on(‘touchend MSPointerUp pointerup‘, function(e) {
if ((_isPointerType = isPointerEventType(e, ‘up‘)) && !isPrimaryTouch(e)) return
cancelLongTap()
// swipe
if ((touch.x2 && Math.abs(touch.x1 - touch.x2) > 30) ||
(touch.y2 && Math.abs(touch.y1 - touch.y2) > 30))
swipeTimeout = setTimeout(function() {
touch.el.trigger(‘swipe‘)
touch.el.trigger(‘swipe‘ + (swipeDirection(touch.x1, touch.x2, touch.y1, touch.y2)))
touch = {}
}, 0)
// normal tap
else if (‘last‘ in touch)
// don‘t fire tap when delta position changed by more than 30 pixels,
// for instance when moving to a point and back to origin
if (deltaX < 30 && deltaY < 30) {
// delay by one tick so we can cancel the ‘tap‘ event if ‘scroll‘ fires
// (‘tap‘ fires before ‘scroll‘)
tapTimeout = setTimeout(function() {
// trigger universal ‘tap‘ with the option to cancelTouch()
// (cancelTouch cancels processing of single vs double taps for faster ‘tap‘ response)
var event = $.Event(‘tap‘)
event.cancelTouch = cancelAll
touch.el.trigger(event)
// trigger double tap immediately
if (touch.isDoubleTap) {
if (touch.el) touch.el.trigger(‘doubleTap‘)
touch = {}
}
// trigger single tap after 250ms of inactivity
else {
touchTimeout = setTimeout(function() {
touchTimeout = null
if (touch.el) touch.el.trigger(‘singleTap‘)
touch = {}
}, 250)
}
}, 0)
} else {
touch = {}
}
deltaX = deltaY = 0
})
// when the browser window loses focus,
// for example when a modal dialog is shown,
// cancel all ongoing events
.on(‘touchcancel MSPointerCancel pointercancel‘, cancelAll)
// scrolling the window indicates intention of the user
// to scroll, not tap or swipe, so cancel all ongoing events
$(window).on(‘scroll‘, cancelAll)
})
;
[‘swipe‘, ‘swipeLeft‘, ‘swipeRight‘, ‘swipeUp‘, ‘swipeDown‘,
‘doubleTap‘, ‘tap‘, ‘singleTap‘, ‘longTap‘
].forEach(function(eventName) {
$.fn[eventName] = function(callback) {
return this.on(eventName, callback)
}
})
})(Zepto)

效果就实现了

Zepto.js touch,tap增加 touch模块深入分析