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

没那么复杂。

请试试这个:

$(document).ready(function(){
    var modalId = "#myModal";
    resize: function(){
            var new_margin = Math.ceil(($(window).height() - $(modalId).find('.modal-dialog').height()) / 2);
            $(modalId).find('.modal-dialog').css('margin-top', new_margin + 'px');
    }
    $(window).resize(function(){
        resize();
    });
    $(modalId).on('shown.bs.modal', function(){
        resize();
    });
});

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;
}

一个简单的方法。为我工作。谢谢rensdenobel:) http://jsfiddle.net/rensdenobel/sRmLV/13/

<style>
.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;
}
</style>
<!-- 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>    

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;
}

它可以简单地可以固定显示:伸缩

.modal-dialog {
  margin-top: 0;
  margin-bottom: 0;
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.modal.fade .modal-dialog {
  transform: translate(0, -100%);
}

.modal.in .modal-dialog {
  transform: translate(0, 0);
}

与前缀

.modal-dialog {
  margin-top: 0;
  margin-bottom: 0;
  height: 100vh;
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
  -webkit-flex-direction: column;
      -ms-flex-direction: column;
          flex-direction: column;
  -webkit-box-pack: center;
  -webkit-justify-content: center;
      -ms-flex-pack: center;
          justify-content: center;
}

.modal.fade .modal-dialog {
  -webkit-transform: translate(0, -100%);
          transform: translate(0, -100%);
}
.modal.in .modal-dialog {
  -webkit-transform: translate(0, 0);
          transform: translate(0, 0);
}