Question

I am trying to implement this great technique of sharing preferences across two different applications while still MODE_PRIVATE.

My problem is that the first application cannot assume that the first application is installed (and vice versa) and so:

 Context c = createPackageContext("com.app.first", MODE_PRIVATE);

Must be replaced by:

 Context c = createPackageContext("com.app.shared", MODE_PRIVATE);

But that mandates adding that com.app.shared for real, which translates into a second APK?

In other words, there is only one AndroidManifest.xml per APK and only one <manifest package= > per manifest file. Therefore only one actual package per APK?

I don’t want 2 APKs per application, I only want a single APK per application.

Is there a way to achieve this?

Answer 1

I am trying to implement this great technique of sharing preferences across two different applications while still MODE_PRIVATE.

Actually, that is such an anti-great technique that I just deleted my answer. Using android:sharedUserId is risky, and downright impossible for already-deployed apps. I learned the error of my ways in the two years since I had posted my answer there.

Also, the technique doesn’t work reliably, because you have no control over which apps the user installs… and uninstalls. If App A and App B share preferences by means of both using App A’s copy, then when the user uninstalls App A, App B is hosed.

Therefore only one actual package per APK?

Correct.

I don’t want 2 APKs per application, I only want a single APK per application.

For two applications, you have two APK files, each with their own package name.