CSSbackgroudn过渡，这里有什么问题？-CSSbackgroudntransition,what'swronghere?

1  

background images can't be “transitioned” like other properties: what should be an intermediate value of a background-image during a transition?

背景图像不能像其他属性一样“过渡”:在过渡期间应该是背景图像的中间值?

As a workaround you could apply the background to a pseudoelement, with position: absolute and a negative z-index. Then you can show the pseudoelement by animating its opacity property, like so

作为一种解决方法,您可以将背景应用于伪元素,其中position:absolute和negative z-index。然后,您可以通过设置其opacity属性的动画来显示伪元素,就像这样

https://jsfiddle.net/45vdd8fL/4/

.flowItem {
    position: relative;
}

.flowItem::before {
    -webkit-transition: opacity 1s linear;
    -moz-transition: opacity 1s linear;
    -ms-transition: opacity 1s linear;
    -o-transition: opacity 1s linear;
    transition: opacity 1s linear;

    content: "";
    position: absolute;
    z-index: -1;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0;   
    background-image: -moz-linear-gradient(top, #E0FFFF, #87CEEB);
    background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0.00, #E0FFFF), color-stop(1.0, #87CEEB));

}

.flowItem:hover::before {
   opacity: 1; 
}

1  

background-image is not an animatable property. You’ll need to find some other way; for example, an element with an opacity transition to act as the background.

background-image不是可动画的属性。你需要找到其他方式;例如,具有不透明度过渡的元素充当背景。

.flowItem {
    position: relative;
    z-index: 0;
}

.flowItem::before {
    background-image: linear-gradient(#E0FFFF, #87CEEB);
    bottom: 0;
    content: '';
    left: 0;
    opacity: 0;
    position: absolute;
    right: 0;
    top: 0;
    transition: opacity 1s linear;
    z-index: -1;
}

.flowItem:hover::before {
    opacity: 1;
}

Updated fiddle