css parent/child 有问题

Question

我在使用 css parent/child 时遇到了问题：

bg.className = "centrer";
bg.style.backgroundColor = "blue";

var container = document.createElement("div");
container.className = 'container';
container.style.height = '100px';
container.style.width = '110px';
var inner = document.createElement("div");
inner.className = 'inner';
var title = document.createElement("p");
title.textContent = "Test";
title.className = 'centrerTitre';
title.style.color = 'black';
inner.appendChild(title);
container.appendChild(inner);

bg.appendChild(container);

document.getElementById('bar').addEventListener("change", function(){
  bg.style.opacity = this.value/100;
  container.style.opacity = 1;
  document.getElementById('valeurBar').innerHTML = this.value + "%";
}, false);

.centrer {
    display: block;
    margin: auto;
    position: absolute;
    top: 0; bottom: 0; left: 0; right: 0;
 height : 250px;
 width : 500px;
    text-align : center;
}

.container:before {
  content: "";
  display: inline-block;
  vertical-align: middle;
  height: 100%;
}

.container {
    position:absolute !important;
    border:3px solid black;
    opacity : 1;
}

.centrer > div {
 opacity:1;
}

.inner {
 display: inline-block;
 vertical-align: middle;
 text-align:center;
 width:100%;
}

.centrerTitre{
 font-size: 25;
    font-weight: bold;
 color : white;
 margin : auto;
 text-align : center;
 padding-left : 4px;
 padding-right : 4px;
}

Opacity : <input type='range' min='0' max='100' value='100' style='width:250px' id='bar'><span id='valeurBar'>100%</span>
<div id="bg"></div>

我有一个divchild变成了一个divparent。我们可以用值 bar 改变 parent 的不透明度。但是当我们这样做时，child 的不透明度也会改变。我试着输入 css : .centrer > div { opacity : 1;但这没有用，我也试着把 container.style.opacity = 1; 给听众但这也行不通。

如何在不更改 child 的不透明度的情况下单独更改 parent 的不透明度？

感谢您的关注。

编辑：很抱歉为了您的理解我简化了我的问题，通常背景是图像而不仅仅是颜色。我怎样才能用图像来解决这个问题？（基本上，我就这样走了，因为我不知道我是否可以上传图片...）

Answer 1

如果您更改 parent 的不透明度，后代将受到影响。但是你可以做一个技巧来改变parent的背景不透明度。

编辑：图像背景的解决方案

如果您的背景是图片，您可以创建一个填充 div 的图片作为背景，并像这样更改其不透明度。 Demo

HTML

<input type='range' min='0' max='100' value='100' style='width:250px' id='bar'><span id='valeurBar'>100%</span>

JS

var bg = document.getElementById('bg');
bg.className = "centrer";
bg.style.backgroundColor = "blue";

var imageBackground = document.createElement("div");
imageBackground.className = 'image-background';
imageBackground.style.height = '100%';
imageBackground.style.width = '100%';
bg.appendChild(imageBackground);


var container = document.createElement("div");
container.className = 'container';
container.style.height = '100px';
container.style.width = '110px';


var inner = document.createElement("div");
inner.className = 'inner';
var title = document.createElement("p");
title.textContent = "Test";
title.className = 'centrerTitre';
title.style.color = 'black';
inner.appendChild(title);
container.appendChild(inner);

bg.appendChild(container);

document.getElementById('bar').addEventListener("change", function(){

  imageBackground.style.opacity = this.value/100;
  document.getElementById('valeurBar').innerHTML = this.value + "%";
}, false);

CSS

.centrer {
    display: block;
    margin: auto;
    /* position: absolute; */
    top: 0; bottom: 0; left: 0; right: 0;
    height : 250px;
    width : 500px;
    text-align : center;
     position:relative;
}

.container:before {
  content: "";
  display: inline-block;
  vertical-align: middle;
  height: 100%;
}

.container {
    position:absolute !important;
    border:3px solid black;
    background: blue;
}

.inner {
    display: inline-block;
    vertical-align: middle;
    text-align:center;
    width:100%;
}

.centrerTitre{
    font-size: 25;
    font-weight: bold;
    color : white;
    margin : auto;
    text-align : center;
    padding-left : 4px;
    padding-right : 4px;
}

.image-background{
    position:absolute;
  background: url("https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRCbA4ze7ExrnpgnTxMSBiifLg_TLz3HRLycnlmTWHkvMwcY5X2nZrI_w");
}

Answer 2

但是您可以将背景颜色更改为 RGBA 值以获得此：

bg.className = "centrer";
bg.style.backgroundColor = "blue";
var container = document.createElement("div");
container.className = 'container';
container.style.height = '100px';
container.style.width = '110px';
var inner = document.createElement("div");
inner.className = 'inner';
var title = document.createElement("p");
title.textContent = "Test";
title.className = 'centrerTitre';
title.style.color = 'black';
inner.appendChild(title);
container.appendChild(inner);

bg.appendChild(container);

document.getElementById('bar').addEventListener("change", function(){
  
  bg.style.backgroundColor = "rgba(0,0,255," + this.value/100 + ")";
  container.style.opacity = 1;
  document.getElementById('valeurBar').innerHTML = this.value + "%";
}, false);

.centrer {
    display: block;
    margin: auto;
    /* position: absolute; */
    top: 0; bottom: 0; left: 0; right: 0;
 height : 250px;
 width : 500px;
    text-align : center;
}

.container:before {
  content: "";
  display: inline-block;
  vertical-align: middle;
  height: 100%;
}

.container {
    position:absolute !important;
    border:3px solid black;
    background: blue;
}

.inner {
 display: inline-block;
 vertical-align: middle;
 text-align:center;
 width:100%;
}

.centrerTitre{
 font-size: 25;
    font-weight: bold;
 color : white;
 margin : auto;
 text-align : center;
 padding-left : 4px;
 padding-right : 4px;
}

Opacity : <input type='range' min='0' max='100' value='100' style='width:250px' id='bar'><span id='valeurBar'>100%</span>
<div id="bg"></div>

Answer 3

恐怕当你改变父不透明度时，你也会改变所有后代节点。

我会做的是将 'bd' div 从容器中分离出来，然后重叠位置...像这样：

bg.className = "centrer";
bg.style.backgroundColor = "blue";

var container = document.createElement("div");
container.className = 'container';
container.style.backgroundColor = bg.style.backgroundColor;
container.style.height = '100px';
container.style.width = '110px';
var inner = document.createElement("div");
inner.className = 'inner';
var title = document.createElement("p");
title.textContent = "Test";
title.className = 'centrerTitre';
title.style.color = 'black';
inner.appendChild(title);
container.appendChild(inner);

bg.parentNode.appendChild(container);

document.getElementById('bar').addEventListener("change", function(){
  bg.style.opacity = this.value/100;
  container.style.opacity = 1;
  document.getElementById('valeurBar').innerHTML = this.value + "%";
}, false);

.centrer {
    display: block;
    margin: auto;
    position: absolute;
    top: 0; bottom: 0; left: 0; right: 0;
 height : 250px;
 width : 500px;
    text-align : center;
}

.container:before {
  content: "";
  display: inline-block;
  vertical-align: middle;
  height: 100%;
}

.container {
    display: block;
    margin: auto;
    position: absolute;
    top: 0; bottom: 0; left: 0; right: 0;
    border:3px solid black;
    opacity : 1;
}

.centrer > div {
 opacity:1;
}

.inner {
 display: inline-block;
 vertical-align: middle;
 text-align:center;
 width:100%;
}

.centrerTitre{
 font-size: 25;
    font-weight: bold;
 color : white;
 margin : auto;
 text-align : center;
 padding-left : 4px;
 padding-right : 4px;
}

Opacity : <input type='range' min='0' max='100' value='100' style='width:250px' id='bar'><span id='valeurBar'>100%</span>
<div id="bg"></div>

css parent/child 有问题

Trouble with the css parent/child

html

javascript

css

opacity