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

扩展@Finik的精彩回答,这个修复只适用于非移动设备。我在IE8、Chrome和Firefox 22上进行了测试——它可以处理很长或很短的内容。

.modal {
  text-align: center;
}
@media screen and (min-device-width: 768px) {
  .modal:before {
    display: inline-block;
    vertical-align: middle;
    content: " ";
    height: 100%;
  }
}

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

其他回答

使用这个简单的脚本将情态动词居中。

如果你愿意,你可以设置一个自定义类(例如:.modal。mode -vcenter(而不是.modal)来限制某些模式的功能。

var modalVerticalCenterClass = ".modal";

function centerModals($element) {
    var $modals;
    if ($element.length) {
    $modals = $element;
    } else {
    $modals = $(modalVerticalCenterClass + ':visible');
}
$modals.each( function(i) {
    var $clone = $(this).clone().css('display', 'block').appendTo('body');
    var top = Math.round(($clone.height() - $clone.find('.modal-content').height()) / 2);
    top = top > 0 ? top : 0;
    $clone.remove();
    $(this).find('.modal-content').css("margin-top", top);
    });
}
$(modalVerticalCenterClass).on('show.bs.modal', function(e) {
    centerModals($(this));
});
$(window).on('resize', centerModals);

还添加了这个CSS修复模式的水平间距;我们在模态上显示滚动,主体滚动被Bootstrap自动隐藏:

/* scroll fixes */
.modal-open .modal {
    padding-left: 0px !important;
    padding-right: 0px !important;
    overflow-y: scroll;
}

如果您可以使用flexbox,那么这应该有助于解决问题。

.modal-dialog {
  height: 100%;
  width: 100%;
  display: flex;
  align-items: center;
}

.modal-content {
  margin: 0 auto;
}

.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/

我写的最普遍的解。动态计算对话框高度。(下一步可能是重新计算窗口大小的对话框的高度。)

JSfiddle: http://jsfiddle.net/8Fvg9/3/

// initialise on document ready
jQuery(document).ready(function ($) {
    'use strict';

    // CENTERED MODALS
    // phase one - store every dialog's height
    $('.modal').each(function () {
        var t = $(this),
            d = t.find('.modal-dialog'),
            fadeClass = (t.is('.fade') ? 'fade' : '');
        // render dialog
        t.removeClass('fade')
            .addClass('invisible')
            .css('display', 'block');
        // read and store dialog height
        d.data('height', d.height());
        // hide dialog again
        t.css('display', '')
            .removeClass('invisible')
            .addClass(fadeClass);
    });
    // phase two - set margin-top on every dialog show
    $('.modal').on('show.bs.modal', function () {
        var t = $(this),
            d = t.find('.modal-dialog'),
            dh = d.data('height'),
            w = $(window).width(),
            h = $(window).height();
        // if it is desktop & dialog is lower than viewport
        // (set your own values)
        if (w > 380 && (dh + 60) < h) {
            d.css('margin-top', Math.round(0.96 * (h - dh) / 2));
        } else {
            d.css('margin-top', '');
        }
    });

});
$('#myModal').on('shown.bs.modal', function() {
    var initModalHeight = $('#modal-dialog').outerHeight(); //give an id to .mobile-dialog
    var userScreenHeight = $(document).outerHeight();
    if (initModalHeight > userScreenHeight) {
        $('#modal-dialog').css('overflow', 'auto'); //set to overflow if no fit
    } else {
        $('#modal-dialog').css('margin-top', 
        (userScreenHeight / 2) - (initModalHeight/2)); //center it if it does fit
    }
});