In Android studio 0.8.0 you should enable ADB integration through Tools -> Android, before run your app. Then the log cat will work correctly. Notice that if you make ADB integration disabled while your app is running and again make it enable, then the log cat dosen't show anything unless you rebuild your project.

Restart the phone. And it solves magically

I was using Lenovo A7000plus powered by Android 6.0 M and found out that my Android Studio was unable to record the debug process, but somehow other's phone debug report could be recorded. Plus, I tried use Memu emulator and it recorded normally.

Strangely, that device was recognized by Android Studio and ready to be debugged, but no recorded debug report at all from all application that ran on the device. Of course, USB debug was tuned on.

What I did before, I turned off Developer option on that phone in order to play my favourite mobile game (F/GO) which forbids USB Debugging is turned on in the device.

A few hours later, after trying any method in Internet and not success, accidentally I found simple but strange solution that is Restart the phone. I restarted the phone while it was connecting to PC, and somehow the logcat showed all debug process in Logcat like normal.

It sounds like non-engineering solution at all, but that's really work for my case.

As of 0.4.0 I have noticed that the logcat tab does not work in the debugger window - only in the Android DDMS window (hit Alt+6 to bring up the working logcat while debugging). Awkward I know :)