I am using genymotion emulator http://www.genymotion.com/ but when I opened the camera , I got message \"cannot connect to the camera \" , what is the problem ?
If all the other solutions do not seem to work you can keep the virtual device working and restart eclipse, and the adb process and it should work. It worked for me. My guess is that the connection to adb is already taken by some other camera and that's blocking your current camera from connecting to the IDE development with the virtual device.
If you are using Intellij Idea no need to restart Genymotion or IDE.
It should works for you as well.