css - 如何在带有 url 背景的速记属性中使用 "background-size : contain"。？

Question

下面的 css 与 contain 一起工作，因为它单独作为 background-size 给出，但不是通过使用在 background 中给出的简写

连我也很想知道CSS中background的参数顺序属性

body { 
    background: #00ff00 url("smiley.gif") no-repeat fixed center;
    background-size:contain,contain; 
}

 body { 
    background: #00ff00 url("smiley.gif") no-repeat contain,contain fixed center; 
}  

but this is not working as i tried this shorthand method as above 

<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>
<p>This is some text</p>

单独使用没有问题，但需要知道是否有任何方法可以使用 background-size:contain 简写 background 属性

即使您可以通过更改 W3School 的示例来检查它，这里是它的 url

click to check your way

Answer 1

background: #00ff00 url("smiley.gif") no-repeat fixed center / contain; 

这应该有效。