Eclipse Logcat: only shows "Device disconnected"

Android Programming (3rd Edition) 3. The Activity Lifecycle
1

When I run GeoQuiz, the only output I got from Logcat is "Device Disconnected"
I tried several ways to fix this but they didn’t work

  1. Click the device, aka the emulator, but still nothing;
  2. Reset ADB, didn’t work either.

This’s really frustrating… So, please, anybody can help?