/*iPhone X 适配*/
@media only screen and (device-width: 375px) and (device-height: 812px) and (-webkit-device-pixel-ratio: 3) {
 .fixed-bottom{
 bottom: 37px;
 }
}
/*iPhone XS max 适配*/
@media only screen and (device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio:3) {
 .fixed-bottom{
 bottom: 37px;
 }
}
/*iPhone XR max 适配*/
@media only screen and (device-width: 414px) and (device-height: 896px) and (-webkit-device-pixel-ratio:2) {
 .fixed-bottom{
 bottom: 37px;
 }
}

<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no, viewport-fit=cover">

.fixed-bottom{
 bottom: 0;
 bottom: constant(safe-area-inset-bottom);
 bottom: env(safe-area-inset-bottom);
}