zepto的tap事件的点透问题的几种解决方案
十度 HTML 2016年03月29日
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1、“点透”是什么
你可能碰到过在列表页面上创建一个弹出层，弹出层有个关闭的按钮，你点了这个按钮关闭弹出层后后，这个按钮正下方的内容也会执行点击事件（或打开链接）。这个被定义为这是一个“点透”现象。
在前面的项目中遇到了如下图的问题：在点击弹出来的选择组件的右上角完成后会让完成后面的input输入框聚焦，弹出输入键盘，也就是点透了
2、为什么会出现点透呢？
这个需要从zepto(或者jqm)源码里面看关于tap的实现方法：
- $(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) }
- })
可以看出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\touchend)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，也就出现了上面的点透现象。
3、点透的解决方法：
方案一：来得很直接github上有个fastclick可以完美解决https://github.com/ftlabs/fastclick
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
- window.addEventListener( "load", function() {
- FastClick.attach( document.body );
- }, false );
或者有zepto或者jqm的js里面加上
- $(function() {
- FastClick.attach(document.body);
- });
当然require的话就这样：
- var FastClick = require("fastclick");
- FastClick.attach(document.body, options);
方案二：用touchend代替tap事件并阻止掉touchend的默认行为preventDefault()
- $("#cbFinish").on("touchend", function (event) {
- //很多处理比如隐藏什么的
- event.preventDefault();
- });
方案三：延迟一定的时间(300ms+)来处理事件
- $("#cbFinish").on("tap", function (event) {
- setTimeout(function(){
- //很多处理比如隐藏什么的
- },360);
- });
这种方法其实很好，可以和fadeInIn/fadeOut等动画结合使用，可以做出过度效果
理论上上面的方法可以完美的解决tap的点透问题，如果真的倔强到不行，用click
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