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

Or if you want to hide/show the title bar at any point:

private void toggleFullscreen(boolean fullscreen)
{
    WindowManager.LayoutParams attrs = getWindow().getAttributes();
    if (fullscreen)
    {
        attrs.flags |= WindowManager.LayoutParams.FLAG_FULLSCREEN;
    }
    else
    {
        attrs.flags &= ~WindowManager.LayoutParams.FLAG_FULLSCREEN;
    }
    getWindow().setAttributes(attrs);
}