javascript - 聚焦文本框时表单元素会波动

Question

我正在尝试实现输入框的具体化样式，即当单击文本框时，标签会向上移动并通过动画减小其字体大小。

我能够实现它，但发生的事情是，当我点击输入框时，标签向上移动，同时发生波动，如表单元素向上移动 2px。

我该如何解决这个问题？这是我当前的代码:

$(document).ready(function(){
        $("input").focus(function(){
            $(this).parent().find("label").addClass('active_text_field');
        });

        $("input").focusout(function(){
            if ($(this).val() == '') {
                $(this).parent().find("label").removeClass('active_text_field');
            };
        }); 
})

.contact_form{  
    position: absolute;
    display: block;
    top:0;
    bottom: 0;
    left: 0;
    right: 0;
    margin: auto;
    width: 50%;
    height:500px;
}

.form-item label{
    display: block;
    font-size: 18px;
    font-family: roboto;
    position: relative;
    top: 30px;
    -moz-transition: all ease-in-out 200ms;
    -webkit-transition: all ease-in-out 200ms;
    transition: all ease-in-out 200ms;
}

.form-item input{
    width:100%;
    outline:none;
    height:36px;
    border:none;
    border-bottom: solid black 1px;
}

.active_text_field{
    transform: translateY(-30px);        
    -moz-transition: all ease-in-out 200ms;
    -webkit-transition: all ease-in-out 200ms;
    transition: all ease-in-out 200ms;
    font-size: 16px !important;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div class="contact_form">
    <form>
        <div class="form-item">
            <label for="firstName">
                First Name
            </label>
            <input type="text" name="firstName" class="text-field">
        </div>

        <div class="form-item">
            <label for="lastName">
                Last Name
            </label>
            <input type="text" name="lastName" class="text-field">
        </div>

        <div class="form-item">
            <label for="email">
                Email
            </label>
            <input type="text" name="email" class="text-field">
        </div>

        <div class="form-item">
            <label for="confirmEmail">
                Confirm Email
            </label>
            <input type="text" name="confirmEmail" class="text-field">
        </div>
    </form>
</div>

Answer 1

只需使用适当的 CSS 来制作 position。这是 JSFiddle链接 我认为你想用你的代码来实现。

此外，使用您的 label display 属性到 inline-block 以便当有人在输入框内的标签旁边单击时更好地 float 标签。

HTML代码-

<div class="contact_form">
    <form>
        <div class="form-item">
            <label for="firstName">
                First Name
            </label>
            <input type="text" name="firstName" class="text-field">
        </div>

        <div class="form-item">
            <label for="lastName">
                Last Name
            </label>
            <input type="text" name="lastName" class="text-field">
        </div>

        <div class="form-item">
            <label for="email">
                Email
            </label>
            <input type="text" name="email" class="text-field">
        </div>

        <div class="form-item">
            <label for="confirmEmail">
                Confirm Email
            </label>
            <input type="text" name="confirmEmail" class="text-field">
        </div>
    </form>
</div>

CSS 代码 -

.contact_form{  
    position: absolute;
    display: block;
    top:0;
    bottom: 0;
    left: 0;
    right: 0;
    margin: auto;
    width: 50%;
    height:500px;
}

.form-item {
    margin-bottom: 20px;
    position: relative;
}

.form-item label{
    display: inline-block;
    font-size: 18px;
    font-family: roboto;
    position: absolute;
    top: 10px;
    -moz-transition: all ease-in-out 200ms;
    -webkit-transition: all ease-in-out 200ms;
    transition: all ease-in-out 200ms;
}

.form-item input{
    width:100%;
    outline:none;
    height:36px;
    border:none;
    border-bottom: solid black 1px;
}

.active_text_field{
    transform: translateY(-30px);        
    -moz-transition: all ease-in-out 200ms;
    -webkit-transition: all ease-in-out 200ms;
    transition: all ease-in-out 200ms;
    font-size: 16px !important;
}

JS代码-

$(document).ready(function(){
        $("input").focus(function(){
            $(this).parent().find("label").addClass('active_text_field');
        });

        $("input").focusout(function(){
            if ($(this).val() == '') {
                $(this).parent().find("label").removeClass('active_text_field');
            };
        }); 
});