html - 过渡不适用于不透明度

Question

所以我有一个带有两个按钮的标题，登录和加入，当用户将鼠标悬停在其中一个按钮上时，我会放下一个带有一些输入和一个按钮的容器。我希望下拉菜单使用 css opacity 淡入淡出，但我无法让它工作也许还有其他更好的方法。谢谢，这是一个fiddle .

HTML:

<div id="membership_container">
    <div id="login_button">
        <span id="login_text">Login</span>
        <div class="form_containers" id="login_box">
            <div class="form_inner_containers">
                <form action="/login" method="POST">
                    <input class="inputs" placeholder="Email" type="text" name="login_email"/>
                    <input class="inputs" placeholder="Password" type="password" name="login_password"/>
                    <input class="buttons" type="submit" value="Login"/>
                </form>
            </div>
        </div>
    </div><!--
    --><div id="join_button">
        <span id="join_text">Join</span>
        <div class="form_containers" id="join_box">
            <div class="form_inner_containers">
                <form action="/join" method="POST">
                    <input class="inputs" placeholder="Your Name" type="text" name="name"/>
                    <input class="inputs" placeholder="Email" type="text" name="email"/>
                    <input class="inputs" placeholder="Password" type="password" name="password"/>
                    <input class="buttons" type="submit" value="Join"/>
                </form>
            </div>
        </div>
    </div>
</div>

CSS:

#membership_container {
    float: right;
    position: relative;
    vertical-align: top;
    display: inline-block;
    height: 100%;
    margin: 0px;
    padding: 0px;
    background-color: #444444;
    text-align: center;
}
#login_button {
    position: relative;
    vertical-align: top;
    display: inline-block;
    float: left;
    height: 100%;
    margin: 0px;
    padding: 0px 10px;
    background-color: #444444;
    border-left: 2px solid #7B7B7B;
    border-right: 2px solid #7B7B7B;
    cursor: pointer;
    cursor: hand;
}
#login_button:hover {
background-color: #696969;
}
#login_button #login_box {
display: none;
opacity: 0.0;
}
#login_button:hover #login_box {
display: block;
opacity: 1;
}
#login_text {
    position: relative;
    margin: 9px 0px 0px;
    text-align: center;
    color: white;
    display: inline-block;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 13px;
}
#join_button {
    position: relative;
    vertical-align: top;
    display: inline-block;
    float: left;
    height: 100%;
    margin: 0px;
    background-color: #444444;
    padding: 0px 10px;
    border-right: 2px solid #7B7B7B;
    cursor: pointer;
    cursor: hand;
}
#join_button:hover {
background-color: #696969;
}
#join_button:hover #join_box {
display: block;
opacity: 1.0;
}
#join_text {
    position: relative;
    margin: 9px 0px 0px;
    text-align: center;
    color: white;
    display: inline-block;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 13px;
}

.button_blur {
    background-color: #444444;
}
.button_blur:hover {
    background-color: #696969;
}
.button_focus {
    background-color: #696969;
}
.form_containers {
    z-index: 10;
    position: absolute;
    display: none;
    opacity: 0.0;
    border: 5px solid #888888;
    border-radius: 10px 0px 10px 10px;
    background-color: #F1F1F1;
    -o-transition: opacity .8s linear;
    -ms-transition: opacity .8s linear;
    -moz-transition: opacity .8s linear;
    -webkit-transition: opacity .8s linear;
    transition: opacity .8s linear;
}
#login_box {
    top: 35px;
    right: -2px;
    /*left: -115px;*/
}
#join_box {
    top: 35px;
    right: -2px;
    /*left: -73px;*/
}
.form_inner_containers {
    position: relative;
    margin: auto auto;
    display: block;
    background-color: #F1F1F1;
    border-radius: 10px;
    border: 0px;
}
.form_hidden {
    display: none;
}
.form_shown {
    display: block;
}
.inputs {
    border-radius: 8px;
    background-color: white !important;
    outline: none;
    border: 0px;
    font-size: 22px;
    padding: 10px;
    margin: 10px;
    box-shadow: 0px 0px 0px grey;
}
.inputs:focus {
    box-shadow: 3px 3px 3px grey;
}
.buttons {
    position: relative: 
    display: block;
    background-color: #00ADEF;
    margin: 10px;
    border-radius: 8px;
    padding: 10px 15px 8px;
    width: 269px;
    outline: none;
    font-size: 22px;
    border: 0px;
    cursor: pointer;
    cursor: hand;
    color: #F1F1F1;
}
.buttons:hover {
    background-color: #18B4EF;
}
.buttons:active {
    background-color: #91D6F0;
    color: #F1F1F1;
    outline: none;
}

Answer 1

包含设置为“display: none;”隐藏它们。在悬停时，它们被设置为“显示: block ”，这会立即显示它们并忽略不透明度过渡。就个人而言，我发现这个“错误”非常烦人(它不是错误......但是，它很烦人)。

两个解决方法是 Javascript(困惑)和使用 CSS 关键帧动画。 http://hschwarz77.wordpress.com/2013/10/16/css-transition-from-display-none-to-display-block-on-hover/

据我所知，这些是使 div 完全隐藏(并且不可用...visibility:hidden 占据空间)并淡入的唯一解决方案。