Sometimes this scenario occurs when developing. I would make a change in my source code, hit save all and then run but the change wouldn't be apparently not reflected in the app -(I'm using a device for testing). I can even uninstall the app on my device, and hit run again and the newly installed app still hasn't reflected the change in the source code. When this happens I have to edit the source, hit run and maybe then a new version with the changes I expected will be on the device.
I also tried the solution here, but it doesn't seem to work often.