我正在尝试为 android 构建一个 epub 阅读器，一切都很好并且按预期工作，但是我无法解决的问题是保存上次看到的页面(或为书签保存位置)。

一点背景:

我使用 css multi column显示 epub，columnWidth设置为 windowWidth和 columnHeight设置为 windowHeight . 确保每一列都填满整个屏幕。

目前为了保存位置，我预处理 html 并用 div 包装每个元素包括特定的 id表示节号和标记位置。例如 <p>处理后的标签是这样的:

<div id="id__1__8"><p>some text</p></div>

id__1__8表示此文本属于第 1 节，并且是该正文中的第 8 个元素。

我有这些 ID 的完整列表，为了保存位置，我使用 jQuery 比较当前列的左侧与每个 id 的左侧所以最近的 id会被找到并且我知道这个页面属于 epub 中的 where。

下一步是找到偏移量(假设一个 p 标签填满了 7 页)。有了偏移量，我知道我必须加载第 1 节的第 8 个元素并转到第 5 页。

查看 jQuery 中的函数:(用于查找最近的元素和偏移量)

jqGetLastPosition = function(ids)
    {
        var tempColumn = _column; // _column is current page that is showing
        if(tempColumn < 0)
        {
            tempColumn = -1 * tempColumn;
        }
        var realIds = ids.split("|");
        var columnLeft = (tempColumn * (_windowWidth + _columnGap));
        var currentLeft;
        var currId = "#" + realIds[0];
        var nearestId = realIds[0] + "__0";
        var minDistance = 1000000;
        var tempDistance = 0;
        var exactColumn = 0;
        for(i=0; i<realIds.length; i++)
        {
            try
            {
                currId = "#" + realIds[i];
                currentLeft = $(currId).position().left;
                if(currentLeft < 0)
                {
                    currentLeft = -1 * currentLeft;
                }
                tempDistance = columnLeft - currentLeft;
                if(tempDistance < 0)
                {
                    //this id is after this page
                    continue;
                }
                else if(tempDistance < minDistance)
                {
                    minDistance = tempDistance;
                    exactColumn = Math.floor(minDistance/(_windowWidth + _columnGap)); //this must compute the offset pages after nearest element
                    nearestId = realIds[i] + "__" + exactColumn;
                }
            }
            catch(e)
            {
            }
        }

        jsSaveLastLocation(nearestId);
    };

此代码适用于页面偏移量为零 的大多数情况，例如id__1__8__0 .

当有offset时，问题就出现了，无法正确计算偏移页，我可以看到有一页偏移，但是这段代码给了我 0 偏移，或者当有 9 页偏移时它给我 4。

那么这段代码有什么问题呢？

或者我这样做是为了保存位置而做错了吗？

有没有更好的方法？

更新:

如果我添加 div在 <div id="id__1__8"></div><p>some text</p> 之类的任何标签之前结果将在 90% 的时间内准确无误。所以更新后的问题将是如何以 100% 的准确度实现这个目标(在 epub 中保存位置)？

更新 2:

我把 div对于每个元素，例如。 head , p , link , img ....

这是否有可能造成问题？

更新 3:

我终于找到了导致问题的原因。考虑到当前页面最近的元素从上一页的中间开始的情况，我保存了这个元素的id，偏移量为1。当我想加载保存的位置时，元素加载在顶部页面，所以文本会发生一点变化，在下图中我展示了正在发生的事情。

任何想法将不胜感激

更新 4:

CSS:

#container {
    width: 100%;
    height: 98%;
    overflow: hidden;
    }
    #content {
    position: relative;
    height: 98%;
    -moz-column-width: 200px;
    -webkit-column-width: 200px;
    column-width: 200px;
    -moz-column-gap: 1px;
    -webkit-column-gap: 1px;
    column-gap: 1px;
    }
    img {
    max-width: 100%;
    max-height: 100%;
    display:inline-block;
    -webkit-column-break-inside : avoid;
    }

<span id=\"endMarker\"></span>将添加到正文的末尾，因此我在 html 内容的末尾有一个标记。

Jquery:

var _column = 0;
var _columnCount = 0;
var _windowWidth;
var _windowHeight;
var rtl = 0;

$(function() {
    _columnWidth = $('#container').width();
    _windowWidth = $('#container').width();
    _windowHeight = $('#container').height();
    $('#content').css('-webkit-column-width', _windowWidth);
    $('#content').css('-moz-column-width', _windowWidth);
    $('#content').css('column-width', _windowWidth);

    $(document).ready(function(){
    $(window).load(function(){
        _columnCount = Math.floor($('#endMarker').position().left/(_windowWidth + _columnGap));
        if(_columnCount < 0)
        {
            rtl = 1;
            _columnCount = (_columnCount * -1);// + 2;
            informRTL(rtl); //inform the java part that this doc is right to left
        }
        else
        {
            informRTL(rtl);
        }
        reportNumberOfPage(_columnCount); // this will report to java part
    });
    });

    setColumn = function(i) {
        if(rtl == 1)
        {
            _column = (i * -1);
        }
        else
        {
            _column = i;
        }

        $('#content').css({"-webkit-transform":"translate(" + (-1 * _column * (_windowWidth + _columnGap)) + "px,0px)"});
    }    

    setColumn(0); //set the showing column to first

    nextPage = function() {
        if (_column==_columnCount -1 || (-1*_column)==_columnCount -1)
            informEndPage();
        else
            {           
                if(rtl == 1)
                {
                    _column = _column-1;
                    $('#content').css({"-webkit-transform":"translate(" + (-1 * _column * (_windowWidth + _columnGap)) + "px,0px)"});                   
                }
                else
                {
                    _column = _column+1;
                    $('#content').css({"-webkit-transform":"translate(" + (-1 * _column * (_windowWidth + _columnGap)) + "px,0px)"});                                                   
                }           
            }           
    };

    prevPage = function() {
        if (0==_column) 
            informStartPage();
        else
            {           
                if(rtl == 1)
                {
                    _column = _column+1;                    
                    $('#content').css({"-webkit-transform":"translate(" + (-1 * _column * (_windowWidth + _columnGap)) + "px,0px)"});
                    updateCurrentPageText((_column * -1));
                }
                else
                {
                    _column = _column-1;                    
                    $('#content').css({"-webkit-transform":"translate(" + (-1 * _column * (_windowWidth + _columnGap)) + "px,0px)"});
                    updateCurrentPageText(_column);
                }                           
            }        
    };

    //this function add more html content to the end of current body
    addString = function(s)
    {
        $(s).insertBefore('#endMarker');
        $(window).load(addStringReport());
    };

    addStringReport = function()
    {
        _columnCount = Math.floor($('#endMarker').position().left/(_windowWidth + _columnGap));
        if(_columnCount == 0)
        {
            requestMorePage();
        }
        if(_columnCount < 0)
        {
            rtl = 1;
            _columnCount = (_columnCount * -1);
        }
        nextPage();
        reportNumberOfPage(_columnCount);
    }

    //this function add more html content to the first of body
    addStringToFirst = function(s)
    {
        $('#content').prepend(s);
        $(window).load(addStringToFirstReport());
    }

    addStringToFirstReport = function()
    {
        maxColumn = Math.floor($('#endMarker').position().left/(_windowWidth + _columnGap));
        if(maxColumn < 0)
        {
            rtl = 1;
            maxColumn = (maxColumn * -1);
            _column = (maxColumn - _columnCount + _column);
        }
        else
        {
            _column = maxColumn - _columnCount + _column;
        }

        _columnCount = maxColumn;
        setColumn(_column);
        reportNumberOfPage(_columnCount);
    }

这几乎是我所有的代码，如果您需要更多请告诉我。

最佳答案

我想我明白你在问什么。您是否正在尝试创建一堆都是一个 HTML 文件的“假”页面？我创建了一个我认为你想要的工作示例。它的工作原理是在您滚动时用当前部分更新 location.hash。当您重新加载时，它应该出现在同一部分(“假”页面)。您需要下载它才能正常运行，因此我将其放在要点中。

这是因为 Stackoverflow 和 JSFiddle 在无法更新 location.hash 的沙箱中获取代码。

这将在您每次滚动到新页面时更新您的浏览器历史记录。我觉得这很烦人，所以我有 HTML5 推送状态设置。这仅适用于网络服务器，但每次滚动到新页面时，它都会将当前 url(和历史记录)替换为可见的“假”页面，因此您没有无限的历史记录。我发布的代码将在您的本地计算机或网络服务器上运行，但在网络服务器上运行效果更好。

要点: https://gist.github.com/Christianjuth/a4e6fad50da54818bbc3

代码:

$(document).scroll(function() {

  //get current section
  var $currentPage = $('.pages > section:onScreen').first();
  var $title = $('.pages > section:onScreen').first().find('h1').first();

  //update url
  if (history && history.pushState && location.protocol !== "file:") {
    history.pushState({}, $title.text(), "/#" + $currentPage.attr('id'));
  } else {
    location.hash = $currentPage.attr('id');
  }
});

html,
body {
  margin: 0;
  padding: 0;
  height: 101%;
  width: 100%;
}
*,
*:before,
*:after {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
.pages {
  display: inline-block;
  width: 100%;
  height: 100%;
}
.pages > section {
  display: inline-block;
  min-height: 100%;
  padding: 10px;
  font-family: Georgia;
}
.pages > section:nth-child(even) {
  background-color: #000;
  color: #fff;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="http://benpickles.github.io/onScreen/jquery.onscreen.js"></script>

<div class="pages">
  <section id="html5">
    <h1>HTML5</h1>

    <p>HTML5 is a core technology markup language of the Internet used for structuring and presenting content for the World Wide Web. As of October 2014 this is the final and complete fifth revision of the HTML standard of the World Wide Web Consortium (W3C).[3]
      The previous version, HTML 4, was standardised in 1997.</p>
    <p>Its core aims have been to improve the language with support for the latest multimedia while keeping it easily readable by humans and consistently understood by computers and devices (web browsers, parsers, etc.). HTML5 is intended to subsume not
      only HTML 4, but also XHTML 1 and DOM Level 2 HTML.</p>
  </section>
  <section id="css3">
    <h1>CSS3</h1>

    <p>Cascading Style Sheets (CSS) is a style sheet language used for describing the look and formatting of a document written in a markup language. While most often used to change the style of web pages and user interfaces written in HTML and XHTML, the
      language can be applied to any kind of XML document, including plain XML, SVG and XUL. Along with HTML and JavaScript, CSS is a cornerstone technology used by most websites to create visually engaging webpages, user interfaces for web applications,
      and user interfaces for many mobile applications.</p>
  </section>
  <section id="bootstrap">
    <h1>Bootstrap</h1>

    <p>Bootstrap is a free and open-source collection of tools for creating websites and web applications. It contains HTML- and CSS-based design templates for typography, forms, buttons, navigation and other interface components, as well as optional JavaScript
      extensions. The bootstrap framework aims to ease web development.</p>
    <p>Bootstrap is a front end, that is an interface between the user and the server-side code which resides on the "back end" or server. And it is a web application framework, that is a software framework which is designed to support the development of
      dynamic websites and web applications.</p>
  </section>
</div>

关于epub 中的 Javascript/JQuery 保存位置，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29486320/