javascript - 需要知道屏幕上显示的是哪个div

Question

我正在实现滑动效果，但通过计算 x、y 坐标来移动上部 div 的位置，然后随屏幕宽度移动包装器(最上面的 div)，因此它看起来像滑动效果。

现在我的问题是我不知道屏幕上显示的下一个 div 中的哪个，我需要对其进行操作，是否有任何方法可以获取 DIV 上显示的当前 div id。

下面是我的JS代码

    (function() {
   var swipey = {
      slideContainer: null, //<ul> element object that holds the image slides
      wrapper: null, //meant for masking/clipping
      slides: null, //array of all slides i.e <li> elements
      distanceX: 0, //distance moved in X direction i.e left or right
      startX: 0, //registers the initial touch co-ordinate
      preferredWidth: 0, //dynamic variable to set width
      preferredHeight: 0, //dynamic variable to set height
      direction: "", //direction of movement
      timer: null, //timer that set starts when touch starts
      timerCounter: 0, //counter variable for timer
      hasSwipeStarted: false, //boolen to chk whether touch has started
      maxDistance: 0, //maximum distance in X direction that slide container can move
      currentDistance: 0, //current distance moved by slide container through translate

      //detect touch and then automatically assign events
      isTouchSupported: 'ontouchstart' in window.document,

      initSwipey: function() {
         //         alert('in initSwipey');
         //scroll the window up to hide the address bar of the browser.
         window.setTimeout(function() {
            window.scrollTo(0, 1);
         }, 100);

         /*mapping touch events to mouse events. Automatic registration of event
            based on the device. If touch enabled then touch event is registered.
            and if desktop browser then mouse event is registered.*/
         swipey.startEvent = swipey.isTouchSupported ? 'touchstart' : 'mousedown',
         swipey.moveEvent = swipey.isTouchSupported ? 'touchmove' : 'mousemove',
         swipey.endEvent = swipey.isTouchSupported ? 'touchend' : 'mouseup',

         //get all the instances of the HTML elements
         swipey.wrapper = document.getElementById("wrapper");
         swipey.slideContainer = document.getElementById("sitePageContainer");
         //swipey.slides = slideContainer.getElementsByTagName("li");
         swipey.slides = document.getElementsByClassName("sitePage");

         //for iPhone, the width and height
         swipey.preferredWidth = window.innerWidth;
         //            alert("swipey.preferredWidth: " + swipey.preferredWidth);
         swipey.preferredHeight = window.innerHeight; //510 for android
         //            alert("swipey.preferredHeight: " + swipey.preferredHeight);
         //setting the width and height to our wrapper with overflow = hidden
         swipey.wrapper.style.width = swipey.preferredWidth + "px";
         //            alert("swipey.wrapper.style.width: " + swipey.wrapper.style.width);
         swipey.wrapper.style.height = swipey.preferredHeight + "px";
         //            alert("swipey.wrapper.style.height: " + swipey.wrapper.style.height);
         //setting the width to our <ul> element which holds all the <li> elements
         swipey.slideContainer.style.height = swipey.preferredHeight + "px";
         //            alert("swipey.slideContainer.style.height: " + swipey.slideContainer.style.height);
         swipey.slideContainer.style.width = swipey.slides.length *  swipey.preferredWidth + "px";
         //            alert("swipey.slideContainer.style.width: " + swipey.slideContainer.style.width);
         //display the <ul> container now
         swipey.slideContainer.style.display = "inline-block";
         //setting width and height for <li> elements - the slides
         for(var i=0;i<swipey.slides.length;i++)
         {
            swipey.slides[i].style.width = swipey.preferredWidth + "px";
            swipey.slides[i].style.height = swipey.preferredHeight + "px";
         }
         //calculating the max distance of travel for Slide Container i.e <ul> element
         swipey.maxDistance = swipey.slides.length * swipey.preferredHeight;
         //initialize and assign the touch events
         swipey.initEvents();
      },
      initEvents: function() {
         //registering touch events to the wrapper



         //$('#wrapper').bind(swipey.startEvent, swipey.startHandler );
         $('#wrapper').bind(swipey.startEvent, function(e){
            $('#wrapper').bind(swipey.moveEvent, swipey.moveHandler );
         } );

         $('#wrapper').bind(swipey.endEvent, swipey.endHandler );
      //swipey.wrapper.addEventListener(swipey.startEvent, swipey.startHandler, false);
      //swipey.wrapper.addEventListener(swipey.moveEvent, swipey.moveHandler, false);
      //swipey.wrapper.addEventListener(swipey.endEvent, swipey.endHandler, false);
      },
      //funciton called when touch start event is fired i.e finger is pressed on the screen
      startHandler: function(event) {
         //create appropriate event object to read the touch/mouse co-ordinates
         var eventObj = swipey.isTouchSupported ? event.touches[0] : event;

         //stores the starting X co-ordinate when finger touches the device screen
         swipey.startX = eventObj.pageX;
         //timer is set on
         swipey.timer = setInterval(function() {
            swipey.timerCounter++;
         }, 10);
         swipey.hasSwipeStarted = true;
         event.preventDefault(); //prevents the window from scrolling.
      },
      //funciton called when touch move event is fired i.e finger is dragged over the screen
      moveHandler: function(event) {
         if (swipey.hasSwipeStarted) {
            //create appropriate event object to read the touch/mouse co-ordinates
            var eventObj = swipey.isTouchSupported ? event.touches[0] : event;

            swipey.distanceX = eventObj.pageX - swipey.startX;
            //move the slide container along with the movement of the finger
            swipey.slideContainer.style.webkitTransform = "translate3d(" + (swipey.distanceX + swipey.currentDistance) + "px, 0,0)";
         }else{
            swipey.startHandler(event);
         }
      },
      //funciton called when touch end event is fired i.e finger is released from screen
      endHandler: function(event) {
         $('#wrapper').unbind(swipey.moveEvent, swipey.moveHandler );
         clearInterval(swipey.timer); //timer is stopped
         if(swipey.distanceX == 0) //if the intention is to tap on the image then open a link
         {
            var link_url = event.target.getAttribute("link"); //read the link from <img /> element
         //  window.open(link_url,"_blank");
         }
         else
         {
            if (swipey.distanceX > 0) {
               swipey.direction = "right";
            }
            if (swipey.distanceX < 0) {
               swipey.direction = "left";
            }
            //the following conditions have been discussed in details
            if ((swipey.direction == "right" && swipey.currentDistance == 0) || (swipey.direction == "left" && swipey.currentDistance == -(swipey.maxDistance - swipey.preferredWidth))) {
               swipey.comeBack();
            }
            else if (swipey.timerCounter < 30 && swipey.distanceX > 10) {
               swipey.moveRight();
            }
            else if (swipey.timerCounter < 30 && swipey.distanceX < -10) {
               swipey.moveLeft();
            }
            else if (swipey.distanceX <= -(swipey.preferredWidth / 2)) { //-160
               swipey.moveLeft();
            }
            else if (swipey.distanceX >= (swipey.preferredWidth / 2)) { //160
               swipey.moveRight();
            }
            else {
               swipey.comeBack();
            }
         }
         swipey.timerCounter = 0; //reset timerCounter
         swipey.hasSwipeStarted = false; //reset the boolean var
         swipey.distanceX = 0; //reset the distance moved for next iteration

         //alert(event.screenX+"::"+event.screenY);
         var element = document.elementFromPoint(event.screenX, event.screenY);
         var $element = $(element);

         alert($element.attr('id'));
         $("div.fixHeader").hide();
         $("#"+$element.attr('id')+" div.fixHeader").show();

      },
      moveLeft: function() {
         swipey.currentDistance += -swipey.preferredWidth;
         swipey.slideContainer.style.webkitTransitionDuration = 300 + "ms";
         //using CSS3 transformations - translate3d function for movement
         swipey.slideContainer.style.webkitTransform = "translate3d(" + swipey.currentDistance + "px, 0,0)";
      },
      moveRight: function() {
         swipey.currentDistance += swipey.preferredWidth;
         swipey.slideContainer.style.webkitTransitionDuration = 300 + "ms";
         swipey.slideContainer.style.webkitTransform = "translate3d(" + swipey.currentDistance + "px, 0,0)";
      },
      comeBack: function() {
         swipey.slideContainer.style.webkitTransitionDuration = 250 + "ms";
         swipey.slideContainer.style.webkitTransitionTimingFunction = "ease-out";
         swipey.slideContainer.style.webkitTransform = "translate3d(" + swipey.currentDistance + "px, 0,0)";
      }
   }; //end of swipey object
   window.swipeyObj = swipey; //expose to global window object
})();

window.onload = function() {
   swipeyObj.initSwipey();
}  //invoke the init method to get started

更新:

下面是结构，现在我正在滑动 sitePageContainer 并且 sitePage 出现在屏幕上，现在我想知道屏幕上显示的是哪个 div(partypicturespage1 或 partypicturespage2)

<div id="wrapper">
         <div id="sitePageContainer">
            <div class="sitePage" id="partypicturespage1"></div>
            <div class="sitePage" id="partypicturespage2"></div>

Answer 1

您可以通过以下方式选择可见的 div:

$("div.fixHeader:visible")

更新:

如果所有 div 都可见，则使用自定义 data-* 属性来跟踪当前 View 中的 div。您可以通过以下方式完成:

$("div.fixHeader").attr('data-visible', true);

并通过以下方式选择它:

$("div.fixHeader[data-visible=true]");

然后删除该属性，这样就不会选择不再显示在 View 中的 div:

$("div.fixHeader[data-visible=true]").attr('data-visible', false);

更新#2:

如果通过设置容器的 left 属性来滚动页面，则通过以下伪代码计算来确定哪个 div 在 View 中:

ceil(scrollContainer.left / divWidth) // if index starts from 1
floor(scrollContainer.left / divWidth) // if index starts from 0