关于iPhonex刘海屏的移动端适配

meta [设置全屏]

<meta name="viewport" content="width=device-width, initial-scale=1.0,viewport-fit=cover"

viewport-fit 的值有 默认值-auto/contain，全屏值-cover

constant() 以及 safe-area-inset-top safe-area-inset-right safe-area-inset-bottom safe-area-inset-left 是 iOS 11 webview 新增加的特性，专门用于应对刘海

   body {

        padding: constant( safe-area-inset-top )  constant( safe-area-inset-right )  constant( safe-area-inset-bottom)  constant( safe-area-inset-left)

}

//默认值

safe-area-inset-top=0，  safe-area-inset-right=44px ， safe-area-inset-bottom=21px， safe-area-inset-left=44px