In this post I outline how to share information solely via email. There's some background information up front; if you're interested in just how to share data only with email apps, skip to the bottom.
One thing that users like to do a lot is share information. They want to be able to post things to Twitter, Facebook, or email their friends. Android makes this really simple via the ACTION_SEND intent:
Intent intent = new Intent(Intent.ACTION_SEND);
intent.putExtra(Intent.EXTRA_SUBJECT, "A Subject");
intent.putExtra(Intent.EXTRA_TEXT, "Here's my message.");
Intent mailer = Intent.createChooser(intent, null);
There's only one issue that arises from this method: any app that's registered to receive the ACTION_SEND intent will show up in the chooser. This means some oddball choices pop up ("Bluetooth" being the weirdest one for me), but that's kind of unavoidable. The bigger issue that I ran into was a matter of message length; Twitter messages are inherently shorter than what I might send via email. If I knew I only had 140 characters, the share message should be a lot shorter; but with the freedom of email, I can template out detailed information.
One solution that I've used is to pop up a dialog which asks the user whether they want a short template message or a long one, with examples of where to use each - short (Twitter, Facebook) vs. long (email).
A bigger problem arises when you want to only share information via emails. Suppose the information your app shares is just too complex for a short Twitter message - an unfortunate circumstance for the Twitter population but a fact of some apps. How do you force the chooser to select email? It turns out that there's a very roundabout way of handling this issue by taking advantage of the mailto protocol in Android:
Intent intent = new Intent(Intent.ACTION_VIEW);
Uri data = Uri.parse("mailto:?subject=" + subject + "&body=" + body);
Using the data scheme that you do, only email apps pick up on this scheme. As a result, only email apps will open. You may not even force the user to go through a chooser if they have a default email app chosen already.