见stackoverflow的一个回答：

http://stackoverflow.com/questions/2160454/helloandroidemulator-5554-disconnected-cancelling-com-example-helloandroid-he


  1. Open Android Virtual Device Manager

  2. select the AVD you use for your app.

  3. Press the start button and wait for a new form to show up called (Launch Options).

  4. Check the box "Wipe user data" and hit "Launch" button.



解决！