Shared preferences between two processes of the same application

Question

I'm writing an Android app that contains both UI and separate processes running. I want to share simple information between the main process and a service defined in my application that is executed in a different process. I find to messy to use AIDL for inter-process communication for this purpose.

The question is: Is it safe to use Shared Preferences of the application for communicating between this two processes? This is: both read and write the same shared preferences.

I'm wondering if it actually works. In android developers reference about shared preferences (http://developer.android.com/reference/android/content/SharedPreferences.html) they state: Note: currently this class does not support use across multiple processes. This will be added later. but I don't know exactly what does this mean.

Thanks for your help

Answer 1

In Android < 2.3 it works. One process can write changes and the other process can read the changes. The code to read/write shared preferences files (they are actually stored in files) checks if there have been any changes made to the file before reading/writing and they update their cached version accordingly.

In Android > 2.3 it works, but you need to specifically set MODE_MULTI_PROCESS when calling getSharedPreferences().

In Android 2.3 it is broken and it doesn't work :-(

Please note that MODE_MULTI_PROCESS is deprecated in API Level 23 (Android M).

Answer 2

You can check out https://github.com/hamsterksu/MultiprocessPreferences library which provides SharedPreferences-like APIs for accessing SharedPreferences data via a ContentProvider. It also looks like a good alternate after Google removed MODE_MULTI_PROCESS from Android 6.