How to hide the title bar for an Activity in XML with existing custom theme

Question

I want to hide the titlebar for some of my activities. The problem is that I applied a style to all my activities, therefore I can\'t simply set the theme to @android:

Answer 1

when i tried to use all those high upvoted answers my app always crashed. (i think it has something to do with the "@android:style"?)

The best solution for me was to use the following:

android:theme="@style/Theme.AppCompat.NoActionBar"

No header / title bar anymore. Just place it in the ... or ... depending if you (don't) want it in the whole app or just a specific activity.