How to make the game don't be visible until some stuff done?

I want to check some thing before the game start. For example: Check if texture is streaming in and don’t let the game visible until fully streaming in. I don’t know how to do it. Is there some function or event will be called to check if game mode can call init game? plz help me.

Do you want to know how to make the screen black?

Will, this maybe a workaround. Actually, I want some knowledge about how game initial and start.