The problem:

http://stackoverflow.com/questions/29677852/connectivitymanager-extra-no-connectivity-is-always-false-on-android-lollipop

The solution:

NetworkAvailability lets you register BroadcastReceiver which works for pre-lollipop and lollipop devices as well.

You have to compile your project at least with AndroidSDK 21:

android{
   compileSdkVersion 21
}

See ExampleActivity.