Android : Android Studio Programming: How to keep displaying all buttons while one button is clicked?

In android studio programming, I want 3 buttons in top of a page and by clicking to a button, it will display corresponding information page (corresponding event took place). However, displaying corresponding information page, all 3 buttons should still appear to users. I mean users do not need to use back key if they want to use other buttons. Please anybody can suggest how to do it? Thank you very much in advance!