I\'ve installed Android Studio in the Applications folder on my Mac (I think the sdk is then in the package content), but now I want to record my screen for a demonstration vide
This point may be helpful for some one else All device do not support screen video recording with android studio. In this regard you can use emulator.
If you are using Android 4.4 or higher you can use adb:
http://developer.android.com/tools/help/adb.html#screenrecord
It can be found in the platform-tools folder under your sdk install folder.
For those of us who need a "Complete Idiot's Guide" in order to find the elusive "Screen Record" button, here it is:
First, make sure you have LogCat
open (Press F6, at least on OSx).
Then you might find that you still don't see any record button. Just hover on the tiny "overflow" arrow seen in the image below.
You should now see the record button, indicated in the image below.
Congratulations, if your device supports screen recording, just click the button and up will pop a dialog asking you to input resolution and bitrate (since this is an "Idiot's Guide", just skip those and click "Start Recording"!).
Connect your Device with your pc via usb.
Open android studio.Ensure that device is connected with adb.
Start click Screen Recording.
Screen Record can record the device display for a maximum of 3 minutes.
Note:
The Screen Record Works with Real Android Device and some Emulators.
If the button is in grey and un-clickable means that device not supports video capture.
The Screenshots from my system: