Question

On Android applications, how to get Registration Id?

Answer 1

Here is a link to the C2DM page. http://code.google.com/android/c2dm/index.html#registering

At the bottom of the page there are links to an example app which uses C2DM.

Basically you need to declare a receiver to receive the registration_id from Google and then fire off a registration request like so:

Intent registrationIntent = new Intent("com.google.android.c2dm.intent.REGISTER");
registrationIntent.putExtra("app", PendingIntent.getBroadcast(this, 0, new Intent(), 0)); // boilerplate
registrationIntent.putExtra("sender", emailOfSender);
startService(registrationIntent);