元素。
我想在我的secundarydiv中添加滚动条，我添加了width和height：
#primary {
width: 100%;
height: 15%;
}
#secundary {
width: 100%;
height: 85%;
overflow: scroll;
}<div id="primary">
<!-- content -->
</div>
<div id="secundary">
<!-- content -->
</div>我尝试使用overflow: scroll属性，但在secundarydiv中看不到任何滚动条。
仅当父元素具有固定的height值时，height的百分比值才有效。目前，#secundary元素是body的子元素，并且body的高度设置为auto- 这是默认值 - 这使得body的高度根据其子元素的高度而变化。
您可以为#secundary或body定义固定高度值。
示例：JSFiddle
试试这段代码：
https://output.jsbin.com/sugelod
#primary {
width: 100%;
height: 15%;
overflow: scroll;
}
#secundary {
width: 100%;
height: 85%;
overflow: scroll;
}
#primary {
width: 100%;
height: 15%;
}
#secundary {
width: 100%;
height: 100px;
overflow: scroll;
}<div id="primary">
<!-- content -->
</div>
<div id="secundary">
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</div>需要有内容的"溢出"： https://developer.mozilla.org/en/docs/Web/CSS/overflow