AFAIK，您无法将其隐藏.这是默认的系统行为(您无法更改)，当用户在屏幕上看到键盘时会显示导航栏.

AFAIK, You can't hide it. This is the default system behavior (you can't change it) to show the navigation bar when on screen keyboard is visible to the user.

提供此按钮是为了使用户可以按导航栏中的后退"按钮以隐藏键盘.因此，只要用户可以看到键盘，它就会一直保留在那里.

It is provided so that the user can press the back button from the navigation bar in order to hide the Keyboard. So, it will stay there forever as long as keyboard is visible to the user.