css3: translateX to center element horizontally

问题

I'm trying to center horizontally an element: jsfiddle

<div id="parent">
    <div id="child">
</div>

On the child I have now the following css which doesn't center:

transform: translateX(50%);

Unfortunately the 50% is taken from the #child and not the parent. Is there a way to center this element using transforms (I know I can center it using, for example 'left')?

Here is the full listing of css

#parent {
    width: 300px
    height: 100px;
    background-color: black;
    border: 1px solid grey;
}
#child {
    height: 100px;
    width: 20px;
    -webkit-transform: translateX(50%);
    background-color:red;
}

回答1:

You were missing a position relative on your parent, position absolute on the child and the left and top values to help offset the child.

DEMO http://jsfiddle.net/nA355/6/

#parent {
    width: 300px;
    height: 100px;
    background-color: black;
    border: 1px solid grey;
    position: relative;
}
#child {
    position: absolute;
    height: 100px;
    width: 20px;
    left: 50%;
    top: 50%;
    -webkit-transform: translateX(-50%) translateY(-50%);
    -moz-transform: translateX(-50%) translateY(-50%);
    transform: translateX(-50%) translateY(-50%);
    background-color:red;
}

回答2:

you can do it on display flex and justify-content is center.

simple: http://jsfiddle.net/ugw9o3qp/1/

#parent {
    display: flex;
    justify-content: center;
    width: 300px;
    height: 100px;
    background-color: black;
    border: 1px solid grey;
}
#child {
    height: 100px;
    width: 20px;
    background-color:red;
}

回答3:

I use this technique to horizontally align some elements in situations where "text-align:center;" does not work correctly.

 position:relative; 
 left:50%;
 transform:translateX(-??em) /*or -??px or other unit of measure */

... "??" has to be tweaked depending on how wide the element is. I know it's kinda hacky, but seems to work on the screens I've tried it on so far.

In your fiddle, applying this technique, I get:

#parent {
    width: 300px
    height: 100px;
    background-color: black;
    border: 1px solid grey;
}
#child {
    position:relative;
    height: 100px;
    width: 20px;
    left:50%;
    transform: translateX(-10px); /*or  transform: translateX(-50%);*/
    -webkit-transform: translateX(-10px);/*or  -webkit-transform: translateX(-50%); */
    -ms-transform: translateX(-10px);/*or -ms-transform: translateX(-50%);*/
    background-color:red;
}

which exactly centers the child div horizontally.

来源：https://stackoverflow.com/questions/20538718/css3-translatex-to-center-element-horizontally

标签

html5

css3

transform

centering