Since version 1.2.2 of Android Stduio, LogCat doesnt appear to be able to only filter the output messages of my app. Instead, it filters all my device messages.
I have Log level "Debug" and "Show only selected application" enabled.
Here's a screenshot of my LogCat: https://i.stack.imgur.com/z8avs.jpg
This is because you see log lines of the whole device.
On the right top side of logcat you see: "Show only selected application". For some reason this does not do what you expect it to do. What I always do is filter on package name.
From this point on you will only see logging of your package.