I recently had trouble with this, and regardless of what I did(restart adb, edit adb_usb.ini, restart computer+device+swap usb port, reinstall studio etc. etc.) I just couldnt get it to work, and could not even detect my device using ‘adb devices’. Finally after about 2 hours of googling and testing, someone suggested switching to PTP instead of MTP on my device. When I did this I got a popup on my device asking me to allow my mac access and suddenly everything worked(had to restart studio for it to show up there as well though).
I might be bumping this thread now, but it is the first result on google search, and I had a lot of trouble finding an answer for this problem, so I thought this should be added as a solution.
On your device:
Go to settings/ developer settings/ allow USB debug mode
If ‘allow USB debug mode’ option is disabled. Then you might have the device currently connected to your PC. Disconnect the device and the option should now be available
Note: On Android 4.2 and newer, Developer options is hidden by default. To make it available, go to Settings > About phone and tap Build number seven times. Return to the previous screen to find Developer options.
If it still doesn’t help, you can google it with this expression:
How to enable developer options on YOUR_PHONE_TYPE
To change what your application defaults to when you click run or debug in Android Studio, follow these steps:
1. go to Run
2. Click on Edit Configurations
3. Select the project
4. find the Target Device section under the General tab on the Android Application page.
That seems to be where you toggle what the project builds to. If you’re importing a project it actually defaults to Emulator, not sure why. You can also select “Open Select Deployment Target Dialog” to list both connected as well as emulated devices.