Question

我在一个基于Bootstrap和jQuery的项目中有一个多级菜单。一切都很好，除了一件事：当一个菜单项放在右边太多时，它的子菜单超出了页面而且不可读（如从jsFiddle截取的屏幕截图所示）：

有没有办法检测子菜单（打开时）是否超出页数限制，如果超过页面限制，是否放在它的父元素的另一侧？

到目前为止我的代码是：

HTML：

Entire%20home

CSS：

<nav class="navbar navbar-default navbar-fixed-top">
    <div class="container">
        <!-- Brand and toggle get grouped for better mobile display -->
        <div class="navbar-header">
            <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>
            <a class="navbar-brand" href="#">LOGO HERE!</a>
        </div>

        <!-- Collect the nav links, forms, and other content for toggling -->
        <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
            <ul class="nav navbar-nav navbar-right">
                <li><a href="/">Home</a></li>
                <li><a href="#">About Us</a></li>
                <li><a href="#">Services</a></li>
                <li class="dropdown">
                    <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Blog <span class="caret"></span></a>
                    <ul class="dropdown-menu">
                        <li><a href="#">Categories</a></li>
                        <li><a href="#">Blog Post</a></li>
                        <li role="separator" class="divider"></li>
                        <li class="dropdown dropdown-submenu">
                            <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Search Engines</a>
                            <ul class="dropdown-menu">
                                <li class="dropdown dropdown-submenu"><a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Google</a>
                                    <ul class="dropdown-menu">
                                        <li><a href="https://adwords.google.com" target="_blank">Google Adwords</a></li>
                                        <li><a href="https://analytics.google.com" target="_blank">Google Analytics</a></li>
                                        <li><a href="https://www.google.com/webmaster/" target="_blank">Webmaster Tools</a></li>
                                    </ul>
                                </li>
                                <li><a href="http://www.yahoo.com">Yahoo</a></li>
                                <li><a href="http://www.msn.com">MSN</a></li>
                            </ul>
                        </li>
                        <li role="separator" class="divider"></li>
                        <li><a href="#">All Tags</a></li>
                    </ul>
                </li>
                <li><a href="#">News</a></li>
                <li><a href="#">Contact</a></li>
            </ul>           
        </div><!-- /.navbar-collapse -->
    </div><!-- /.container -->
</nav>

JS：

.dropdown-menu>li>a:hover{
    background-color:rgba(216,216,216,1);
    background-image:none;
    color:#000;
}
.divider{
    background-color:#fff;
}
.dropdown-submenu{
    position:relative;
}
.dropdown-submenu>.dropdown-menu{
    top:0;
    left:100%;
    margin-top:-6px;
    margin-left:-1px;
    -webkit-border-radius:0 6px 6px 6px;
    -moz-border-radius:0 6px 6px 6px;
    border-radius:0 6px 6px 6px;
}
.dropdown-submenu>a:after{
    display:block;
    content: " ";
    float:right;
    width:0;
    height:0;
    border-color:transparent;
    border-style: solid;
    border-width:5px 0 5px 5px;
    border-left-color: #cccccc;
    margin-top:5px;
    margin-right: -10px;
}
.dropdown-submenu:hover>a:after{
    border-left-color: #555;
}
.dropdown-submenu.pull-left{
    float:none;
}
.dropdown-submenu.pull-left>.dropdown-menu{
    left:100%;
    margin-left:1-0px;
    -webkit-border-radius:6px 0 6px 6px;
    -moz-border-radius:6px 0 6px 6px;
    border-radius:6px 0 6px 6px;
}

在这里测试小提琴：https://jsfiddle.net/311mcf23/

任何帮助将不胜感激。

Answer 1

尝试从css中删除此代码

.dropdown-submenu>.dropdown-menu{
top:0;
left:100%;
margin-top:-6px;
margin-left:-1px;
-webkit-border-radius:0 6px 6px 6px;
-moz-border-radius:0 6px 6px 6px;
border-radius:0 6px 6px 6px;}

Answer 2

在与视口发生碰撞时检测并不容易。我建议像这样移动子菜单..

.dropdown-submenu>.dropdown-menu{top:0;left:-99%;max-width:180px;margin-top:-6px;margin-right:-1px;-webkit-border-radius:6px 6px 6px 6px;-moz-border-radius:6px 6px 6px 6px;border-radius:6px 6px 6px 6px;}
.dropdown-submenu:hover>.dropdown-menu{display:block;}
.dropdown-submenu>a:after{display:block;content:" ";float:left;width:0;height:0;border-color:transparent;border-style:solid;border-width:5px 5px 5px 0;border-right-color:#999;margin-top:5px;margin-right:10px;}
.dropdown-submenu.pull-left>.dropdown-menu{left:-100%;margin-left:0px;-webkit-border-radius:6px 6px 6px 6px;-moz-border-radius:6px 6px 6px 6px;border-radius:6px 6px 6px 6px;}
.dropdown-menu-right {margin-left:0;}

http://www.bootply.com/pho42x2it2

Answer 3

在做了一些研究之后，我遇到了这个话题：How to check if an element is off-screen

根据@Sam Sehnert的建议，我最终使用了可在此处找到的插件：https://github.com/customd/jquery-visible

通过一些小的修改，结果正是我所寻找的！

HTML：

<nav class="navbar navbar-default navbar-fixed-top">
    <div class="container">
        <!-- Brand and toggle get grouped for better mobile display -->
        <div class="navbar-header">
            <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>
            <a class="navbar-brand" href="#">LOGO HERE!</a>
        </div>

        <!-- Collect the nav links, forms, and other content for toggling -->
        <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
            <ul class="nav navbar-nav navbar-right">
                <li><a href="/">Home</a></li>
                <li><a href="#">About Us</a></li>
                <li><a href="#">Services</a></li>
                <li class="dropdown">
                    <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Blog <span class="caret"></span></a>
                    <ul class="dropdown-menu">
                        <li><a href="#">Categories</a></li>
                        <li><a href="#">Blog Post</a></li>
                        <li role="separator" class="divider"></li>
                        <li class="dropdown dropdown-submenu">
                            <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Search Engines</a>
                            <ul class="dropdown-menu">
                                <li class="dropdown dropdown-submenu"><a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Google</a>
                                    <ul class="dropdown-menu">
                                        <li><a href="https://adwords.google.com" target="_blank">Google Adwords</a></li>
                                        <li><a href="https://analytics.google.com" target="_blank">Google Analytics</a></li>
                                        <li><a href="https://www.google.com/webmaster/" target="_blank">Webmaster Tools</a></li>
                                    </ul>
                                </li>
                                <li><a href="http://www.yahoo.com">Yahoo</a></li>
                                <li><a href="http://www.msn.com">MSN</a></li>
                            </ul>
                        </li>
                        <li role="separator" class="divider"></li>
                        <li><a href="#">All Tags</a></li>
                    </ul>
                </li>
                <li><a href="#">News</a></li>
                <li><a href="#">Contact</a></li>
            </ul>           
        </div><!-- /.navbar-collapse -->
    </div><!-- /.container -->
</nav>

CSS：

.dropdown-menu>li>a:hover{
    background-color:rgba(216,216,216,1);
    background-image:none;
    color:#000;
}
.divider{
    background-color:#fff;
}
.dropdown-submenu{
    position:relative;
}
.dropdown-submenu>.dropdown-menu{
    top:0;
    left:100%;
    margin-top:-6px;
    margin-left:-1px;
    -webkit-border-radius:0 6px 6px 6px;
    -moz-border-radius:0 6px 6px 6px;
    border-radius:0 6px 6px 6px;
}
.dropdown-submenu>a:after{
    display:block;
    content: " ";
    float:right;
    width:0;
    height:0;
    border-color:transparent;
    border-style: solid;
    border-width:5px 0 5px 5px;
    border-left-color: #cccccc;
    margin-top:5px;
    margin-right: -10px;
}
.dropdown-submenu:hover>a:after{
    border-left-color: #555;
}
.dropdown-submenu.pull-left{
    float:none;
}
.dropdown-submenu.pull-left>.dropdown-menu{
    left:100%;
    margin-left:1-0px;
    -webkit-border-radius:6px 0 6px 6px;
    -moz-border-radius:6px 0 6px 6px;
    border-radius:6px 0 6px 6px;
}
.rev{
    left:auto !important;
    right:100% !important;
    top:8px !important;
    margin-right:-12px !important;
}

JS：

（函数（$）{

/**
 * Copyright 2012, Digital Fusion
 * Licensed under the MIT license.
 * http://teamdf.com/jquery-plugins/license/
 *
 * @author Sam Sehnert
 * @desc A small plugin that checks whether elements are within
 *       the user visible viewport of a web browser.
 *       only accounts for vertical position, not horizontal.
 */
$.fn.visible = function(partial,hidden,direction,container){

    if (this.length < 1)
        return;

    var $t          = this.length > 1 ? this.eq(0) : this,
                    isContained = typeof container !== 'undefined' && container !== null,
                    $w                = isContained ? $(container) : $(window),
                    wPosition        = isContained ? $w.position() : 0,
        t           = $t.get(0),
        vpWidth     = $w.outerWidth(),
        vpHeight    = $w.outerHeight(),
        direction   = (direction) ? direction : 'both',
        clientSize  = hidden === true ? t.offsetWidth * t.offsetHeight : true;

    if (typeof t.getBoundingClientRect === 'function'){

        // Use this native browser method, if available.
        var rec = t.getBoundingClientRect(),
            tViz = isContained ?
                                            rec.top - wPosition.top >= 0 && rec.top < vpHeight + wPosition.top :
                                            rec.top >= 0 && rec.top < vpHeight,
            bViz = isContained ?
                                            rec.bottom - wPosition.top > 0 && rec.bottom <= vpHeight + wPosition.top :
                                            rec.bottom > 0 && rec.bottom <= vpHeight,
            lViz = isContained ?
                                            rec.left - wPosition.left >= 0 && rec.left < vpWidth + wPosition.left :
                                            rec.left >= 0 && rec.left <  vpWidth,
            rViz = isContained ?
                                            rec.right - wPosition.left > 0  && rec.right < vpWidth + wPosition.left  :
                                            rec.right > 0 && rec.right <= vpWidth,
            vVisible   = partial ? tViz || bViz : tViz && bViz,
            hVisible   = partial ? lViz || rViz : lViz && rViz;

        if(direction === 'both')
            return clientSize && vVisible && hVisible;
        else if(direction === 'vertical')
            return clientSize && vVisible;
        else if(direction === 'horizontal')
            return clientSize && hVisible;
    } else {

        var viewTop                 = isContained ? 0 : wPosition,
            viewBottom      = viewTop + vpHeight,
            viewLeft        = $w.scrollLeft(),
            viewRight       = viewLeft + vpWidth,
            position          = $t.position(),
            _top            = position.top,
            _bottom         = _top + $t.height(),
            _left           = position.left,
            _right          = _left + $t.width(),
            compareTop      = partial === true ? _bottom : _top,
            compareBottom   = partial === true ? _top : _bottom,
            compareLeft     = partial === true ? _right : _left,
            compareRight    = partial === true ? _left : _right;

        if(direction === 'both')
            return !!clientSize && ((compareBottom <= viewBottom) && (compareTop >= viewTop)) && ((compareRight <= viewRight) && (compareLeft >= viewLeft));
        else if(direction === 'vertical')
            return !!clientSize && ((compareBottom <= viewBottom) && (compareTop >= viewTop));
        else if(direction === 'horizontal')
            return !!clientSize && ((compareRight <= viewRight) && (compareLeft >= viewLeft));
    }
};

}）（jQuery的）;

（文档）$。就绪（函数（）{ $（＆＃39; a [data-toggle = dropdown]＆＃39;）。on（＆＃39; click＆＃39;，function（e）{

    e.stopPropagation();
    e.preventDefault();
    $(this).parent().siblings().removeClass('open');
    $(this).parent().toggleClass('open');

    if($(window).width() > 767){

        if($(this).parent('li').hasClass('open')){

            if(!$(this).next('ul').visible()){

                console.log('not visible');
                $(this).next('ul').addClass('rev');

            }

        }else{
            $(this).next('ul').removeClass('rev');
        }

    }

});

}）;

结果可以在这里看到：https://jsfiddle.net/captain_theo/311mcf23/2/

希望能帮助其他有类似问题的人。

西奥

Bootstrap导航子菜单根据页面限制向左或向右浮动

3 个答案: