iOS11 application's header(displayed by Web) disappears

I’m making an iOS application with WebView.

When I scroll the app in iOS11, its header(displayed by Web) disappears.

I want to fix it and make sure it always appears when scrolling the app in iOS11.

My css:

#webview_header

{

position: fixed;

top: 0;

left: 0;

width:100%;

height: 50px;

z-index: 999;

}

I tried some solutions below, but it has not been fixed yet.

- Use transform:translateZ(0) in the header css file

- Use position:absolute instead of position:fixed

- Use position:sticky instead of position:fixed

- Use option viewport-fit: contain/cover/auto

- Set a constant value for the padding-top

- Add -webkit-overflow-scrolling: auto; and overflow-y: auto;

If you know how to solve this problem, please let me know.