I have a particular situation: a service started by a broadcast receiver starts an activity. I want to make it possible for this activity to communicate back to the service.
Yet another cause to the original question might be that the service isn't already running and you are passing 0 as flag to bindService. Like so:
bindService(intent, serviceConnection, 0);
When what you are looking for would be:
bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);