这个问题分为两部分:

当你不知道模态的确切高度时,你如何将模态垂直地放置在中心? 是否有可能有模态居中,并有溢出:auto在模态体,但只有当模态超过屏幕高度?

我试过用这个:

.modal-dialog {
  height: 80% !important;
  padding-top:10%;
}

.modal-content {
  height: 100% !important;
  overflow:visible;
}

.modal-body {
  height: 80%;
  overflow: auto;
}

当内容远远大于垂直屏幕尺寸时,这给了我所需要的结果,但对于较小的模式内容,这几乎是不可用的。


当前回答

还有另一种解决方案,它将为窗口上的每个可见模态设置有效的位置。调整大小事件和show.bs.modal:

(function ($) {
    "use strict";
    function centerModal() {
        $(this).css('display', 'block');
        var $dialog  = $(this).find(".modal-dialog"),
            offset       = ($(window).height() - $dialog.height()) / 2,
            bottomMargin = parseInt($dialog.css('marginBottom'), 10);

        // Make sure you don't hide the top part of the modal w/ a negative margin if it's longer than the screen height, and keep the margin equal to the bottom margin of the modal
        if(offset < bottomMargin) offset = bottomMargin;
        $dialog.css("margin-top", offset);
    }

    $(document).on('show.bs.modal', '.modal', centerModal);
    $(window).on("resize", function () {
        $('.modal:visible').each(centerModal);

    });
})(jQuery);

其他回答

这对我来说很管用:

.modal {
  text-align: center;
  padding: 0!important;
}

.modal:before {
  content: '';
  display: inline-block;
  height: 100%;
  vertical-align: middle;
  margin-right: -4px;
}

.modal-dialog {
  display: inline-block;
  text-align: left;
  vertical-align: middle;
}

您可能想要查看这个div绝对居中的方法集合:http://codepen.io/shshaw/full/gEiDt

.modal { } .vertical-alignment-helper { display:table; height: 100%; width: 100%; } .vertical-align-center { /* To center vertically */ display: table-cell; vertical-align: middle; } .modal-content { /* Bootstrap sets the size of the modal in the modal-dialog class, we need to inherit it */ width:inherit; height:inherit; /* To center horizontally */ margin: 0 auto; } <head> <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script> <link href="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" rel="stylesheet"/> </head> <body> <!-- Button trigger modal --> <button class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">Launch demo modal</button> <!-- Modal --> <div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true"> <div class="vertical-alignment-helper"> <div class="modal-dialog vertical-align-center"> <div class="modal-content"> <div class="modal-header"> <button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span> </button> <h4 class="modal-title" id="myModalLabel">Modal title</h4> </div> <div class="modal-body">...</div> <div class="modal-footer"> <button type="button" class="btn btn-default" data-dismiss="modal">Close</button> <button type="button" class="btn btn-primary">Save changes</button> </div> </div> </div> </div> </div> </body>

CSS:

.modal {
}
.vertical-alignment-helper {
    display:table;
    height: 100%;
    width: 100%;
}
.vertical-align-center {
    /* To center vertically */
    display: table-cell;
    vertical-align: middle;
}
.modal-content {
    /* Bootstrap sets the size of the modal in the modal-dialog class, we need to inherit it */
    width:inherit;
    height:inherit;
    /* To center horizontally */
    margin: 0 auto;
}

HTML:

<!-- Button trigger modal -->
<button class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">Launch demo modal</button>
<!-- Modal -->
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
    <div class="vertical-alignment-helper">
        <div class="modal-dialog vertical-align-center">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span>

                    </button>
                     <h4 class="modal-title" id="myModalLabel">Modal title</h4>

                </div>
                <div class="modal-body">...</div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
                    <button type="button" class="btn btn-primary">Save changes</button>
                </div>
            </div>
        </div>
    </div>
</div>

参考:http://jsfiddle.net/rensdenobel/sRmLV/13/

在我的例子中,我所做的就是在css中设置顶部,知道模态的高度

<div id="myModal" class="modal fade">…< / div >

在我的CSS中

#myModal{
    height: 400px;
    top: calc(50% - 200px) !important;
}

我的解决方案:

.modal.in .modal-dialog 
{
    -webkit-transform: translate(0, calc(50vh - 50%));
    -ms-transform: translate(0, 50vh) translate(0, -50%);
    -o-transform: translate(0, calc(50vh - 50%));
    transform: translate(0, 50vh) translate(0, -50%);
}