html - 具有较低值的 z-index 仍然出现在其他 div 之上

Question

为什么 VideoDivNote仍然出现在VideoDiv即使它的 z-index 较低？使用 <div> 时出现问题或者我在做什么 还有错吗？

<style>

    #VideoDiv
    {position: absolute;
    left: 3%;
    bottom: 5%;
    z-index: 999;
    background-color: #DCDCDC;
    height: 260px;
    width: 424px;
    text-align: center;
    border: 1px solid #d3d3d3;
    -webkit-border-radius: 20px;
    -moz-border-radius: 20px;
    border-radius: 20px;
    }

    #VideoDivNote
    {height: 30px;
    position: relative;
    width: 300px;
    margin: auto;
        left: 0px;
        right: 0px;
        bottom:0px;
    background-color: rgba(8, 8, 8, 0.7);
    -webkit-border-radius: 0px 0px 15px 15px;
    -moz-border-radius: 0px 0px 15px 15px;
    border-radius: 0px 0px 15px 15px;
    z-index: 1;
    }


    #VideoMessage
    {color: #fff;
    font-family: acme;
    position: relative;
    bottom: -6px;
    z-index: 2;
    }

 </style>

    <div id="VideoDiv">

        <div id="VideoPlayer"></div>
        <div id="VideoDivNote"><span id="VideoMessage">z-index not working</span></div>

    </div>

Answer 1

感谢 Temani Afif 的详细解释。 您需要从 #VideoDiv 中删除 z-index 并使用 z-index: -1;在#VideoDivNote id 中。请参阅下文或查看此 link

    #VideoDiv
    {position: absolute;
    left: 3%;
    bottom: 5%;
    background-color: #DCDCDC;
    height: 260px;
    width: 424px;
    text-align: center;
    border: 1px solid #d3d3d3;
    -webkit-border-radius: 20px;
    -moz-border-radius: 20px;
    border-radius: 20px;
    }

    #VideoDivNote
    {height: 30px;
    position: relative;
    width: 300px;
    margin: auto;
        left: 0px;
        right: 0px;
        bottom:0px;
    background-color: rgba(8, 8, 8, 0.7);
    -webkit-border-radius: 0px 0px 15px 15px;
    -moz-border-radius: 0px 0px 15px 15px;
    border-radius: 0px 0px 15px 15px;
    z-index: -1;
    }


    #VideoMessage
    {color: #fff;
    font-family: acme;
    position: relative;
    bottom: -6px;
    z-index: 2;
    }

<div id="VideoDiv">
   <div id="VideoPlayer"></div>
   <div id="VideoDivNote"><span id="VideoMessage">z-index not working</span></div>
</div>