When I run my app from AndroidStudio 0.4.3 using Run I see Choose Device which has two sections choose a running device or Launch Em
Run
Choose Device
choose a running device
Launch Em
Try to kill the adb server and restart it.
Locate your adb binary (linux/osx) or adb.exe (windows) and do:
adb kill-server adb start-server
this should fix your problem
Even if your problem still not solved then Restart emulator.