Bootstrap Center 水平对齐一个 div

Question

I have tried simple login page for a sample. But am unable to align the fields to center. h:commandButton is aligned to center. but rest of the fields are does't have any change while keep <div align="center">

How do i keep them center aligned?

<div align="center">            
    <h:message for="btnSubmit"/>
    <div class='form-row'>
        <div class='col-xs-2 form-group required'>
         <label class='control-label'> User Name </label>
          <h:inputText styleClass="form-control" size="12" maxlength="20" 
                       id="userName" value="#{loginController.userName}" 
                       required="true"/>
        </div>
    </div>

    <div class='form-row'>
        <div class='col-xs-2 form-group card required'>
           <label class='control-label'>Password</label>
           <h:inputText styleClass="form-control" size="12" maxlength="20"
                        id="password" value="#{loginController.password}"
                        required="true" />
         </div>
    </div>

    <div class='form-row'>
        div class='col-md-12 form-group'>
      <h:commandButton styleClass="btn btn-success" 
               value="#{bundle['label.Login']}" id="btnSubmit" 
               action="#{loginController.clientLoginAction}"/>
        </div>
    </div>
</div>

Answer 1

simplest way is to add a custom class .col-center from your side to it

.col-center{
  margin:0 auto;
}

why this way?? because BS has the methodology of offset but it has a drawback as it only works for even column sizes, so only .col-X-2 , .col-X-4 , col-X-6 , col-X-8 and col-X-10 are supported.

Must do : just make sure that whichever div you want to center, has a div width mentioned to it.... .col-center will do rest of job

Answer 2

To center a block level element horizontally in bootstrap use Use center-block class.

For example:

<div class="center-block">...</div>

Answer 3

截至 2019 年 10 月，class="center-block" 已被删除，并在当前引导程序版本中出于相同目的引入了 "mx-auto"。

<div class="mx-auto bg-warning" style="width:150px">Centered</div>