Toolbar - Switching from drawer to back button with only one Activity

Question

I\'ve been searching for a while on how to change between the drawer open/close icon (going from a hamburger to the arrow) to a simple back arrow. My application at the mome

Answer 1

The answer from @matusalem works great. I just had one bit to add to it - be careful because the drawer can also be opened by swiping in from the left side of the screen. For some, this may be desired, but for me I was disabling the drawer because it didn't make sense in any fragment but my main fragment. The swipe is easily disabled here - Navigation drawer - disable swipe

This probably belongs in a comment to the answer, but I don't have enough reputation. My apologies.