I created a webapp-based learning management system, and I'm debating whether a decision I took regarding the top app bar(s) is sound or could cause issues when it comes to user experience and branding of the product.
My app currently has some views where a sidebar is shown on the left in order to navigate, and a top app bar is displayed as well. The top app bar is sticky and always displayed. Here's an example (please disregard the missing UI strings):
On some other views, like the one a student sees while taking an exam, I want to remove the sidebar as I feel that could be distracting and not fit in well with the context of taking an exam.
I still want the user to be able to navigate and have a clue where they are in the app, so I thought of using breadcrumbs. However, putting everything in the top app bar didn't feel right. I decided to have one app bar below with the view title and breadcrumbs. The top app bar isn't sticky on those views, whereas the one below is.
Here's what it look like:
Is it common for apps to use two top bars like in my case? Can you think of any drawbacks on the UX side?
One thing I'm concerned with is that the very top bar disappearing like that can leave the app looking too anonymous, without any hints of branding. I would like something that looks good and is still functional and easy for the user to understand, but I can't come up with anything better.