CSS 网格，绝对定位 css 网格项目中的元素：不可能

Question

我遇到这种情况：https://jsfiddle.net/rozkvsdh/5/

一个CSS网格，很简单，但在某些项目中，我需要放一条丝带或其他div。

这不可能！

我该怎么办？

 grid-item {
  background-color: lightgreen;
  display: flex;
  justify-content: center;
  align-items: center;
}

.ribbon-wrapper {
  width: 85px; // the length should be not in px I think!
  height: 88px; // the length should be not in px I think!
  overflow: hidden;
  //position: absolute; it doesn't work!
  position: relative;
  top: -3px;
  left: -3px;
  .ribbon {
    font: bold 15px sans-serif;
    color: #333;
    text-align: center;
    -webkit-transform: rotate(-45deg);
    -moz-transform: rotate(-45deg);
    -ms-transform: rotate(-45deg);
    -o-transform: rotate(-45deg);
    position: relative;
    padding: 7px 0;
    top: 15px;
    left: -30px;
    width: 120px;
    background-color: #ebb134;
    color: #fff;
  }
}

Answer 1

您需要将 position: relative; 放在 grid-item 上，然后您可以在 .ribbon-wrapper 上使用绝对位置。

grid-item {
  background-color: lightgreen;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

.ribbon-wrapper {
  width: 85px; // the length should be not in px I think!
  height: 88px; // the length should be not in px I think!
  overflow: hidden;
  position: absolute;
  top: -3px;
  left: -3px;
  .ribbon {
    font: bold 15px sans-serif;
    color: #333;
    text-align: center;
    -webkit-transform: rotate(-45deg);
    -moz-transform:    rotate(-45deg);
    -ms-transform:     rotate(-45deg);
    -o-transform:      rotate(-45deg);
    position: relative;
    padding: 7px 0;
    top: 15px;
    left: -30px;
    width: 120px;
    background-color: #ebb134;
    color: #fff;
  }
}

https://jsfiddle.net/thesouthstar86/rozkvsdh/6/

Answer 2

功能区不会左对齐，因为它是具有 justify-content: center 的弹性容器的流入子容器。因此功能区和内容并排居中。

您可以使用 margin-right: auto 覆盖该设置，这将使功能区左对齐，但也会使内容右对齐。

您可以插入一个以在容器中创建平衡，使内容居中。但这有点复杂，可能是不必要的。

坚持使用 CSS 定位属性。这将定位色带。调整大小是另一回事：

grid-item {
    background-color: lightgreen;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative; /* establish nearest positioned ancestor for abspos containment */
}

.ribbon-wrapper {
    overflow: hidden;
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
}

.ribbon-wrapper .ribbon {
    font: bold 15px sans-serif;
    color: #333;
    text-align: center;
    transform: rotate(-45deg);
    position: relative;
    padding: 7px 0;
    top: 15px;
    left: -30px;
    width: 15vw;
    background-color: #ebb134;
    color: #fff;
}

revised fiddle

Answer 3

你可以这样做，也可以调整大小，但有点乱。

间隔 div 在那里，所以你有高度。您需要在每一侧都有一个，因为您希望 PRO 居中。我们在每边牺牲 1px 来完成这项工作，现在 ribbon-wrapper 可以是绝对的

https://jsfiddle.net/rozkvsdh/9/

HTML

<grid-item>

    <div class="ribbon-wrapper"><div class="ribbon">NEW</div></div>    
    <div class="spacer"></div>
    <div>PRO</div>
    <div class="spacer"></div>

</grid-item>

CSS

// this is new
.spacer {
  height: 88px;
  width: 1px;
}

grid-item {
  background-color: lightgreen;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative; // added
}
.ribbon-wrapper {
  width: 85px; // the length should be not in px I think!
  height: 88px; // the length should be not in px I think!
  overflow: hidden;
  position: absolute;
  top: 0; // edited
  left: 0; // edited
}

Answer 4

你可以使用伪造和 data attribute :

HTML5 is designed with extensibility in mind for data that should be associated with a particular element but need not have any defined meaning. data-* attributes allow us to store extra information on standard, semantic HTML elements without other hacks such as non-standard attributes, extra properties on DOM

可以使用溢出，background-clip 可以帮助模仿丝带稍微站在外面

The background-clip CSS property specifies whether an element's background, either the color or image, extends underneath its border.

vmin or vmax units 可用于设置字体大小以通过填充和坐标上的 em 调整功能区大小。

The viewport-percentage lengths are relative to the size of the initial containing block. When the height or width of the initial containing block is changed, they are scaled accordingly.

最终，可以添加shadow，linear-gradient可以帮助绘制倾斜的阴影部分。

演示：

body {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  grid-auto-rows: 1fr;
  grid-gap: 2px;
  height: 100vh;
  padding: 5px;
  margin: 0;
  box-sizing: border-box;
}

grid-item {
  background-color: lightgreen;
  background-clip: content-box;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  overflow: hidden;
  padding: 3px;
}

grid-item[data-class="new"]:before {
  content: attr(data-class);
  position: absolute;
  font-size: 2vmax; /* update font-size */
  top: 0.4em;
  left: -1.3em;
  padding: 0em 1.5em;
  transform: rotate(315deg);
  background-color:gold;
  /* eventually add some shadow effects */
  background-image: 
  linear-gradient(135deg, black 0.9em, transparent 1.15em), 
  linear-gradient(-135deg, black 0.9em, transparent 1.15em);
  box-shadow: 0 0 3px;
}

<grid-item>see</grid-item>
<grid-item>full</grid-item>
<grid-item>page</grid-item>
<grid-item>then</grid-item>
<grid-item data-class="new">RESIZE</grid-item>
<grid-item>window</grid-item>
<grid-item>to</grid-item>
<grid-item>see</grid-item>
<grid-item>ribbon</grid-item>
<grid-item data-class="new">font&size</grid-item>
<grid-item>updates</grid-item>
<grid-item>F</grid-item>
<grid-item data-class="new">PRO</grid-item>
<grid-item>B</grid-item>
<grid-item>C</grid-item>
<grid-item>D</grid-item>
<grid-item>E</grid-item>
<grid-item>F</grid-item>
<grid-item>A</grid-item>
<grid-item>B</grid-item>

CSS 网格，绝对定位 css 网格项目中的元素：不可能

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