How can I share a SharedPreferences file across two different android apps?

android android-intent sharedpreferences android-context
matt5784 picture matt5784 · Jun 14, 2012 · Viewed 24.9k times · Source

I've been struggling with this for a while. Basically, I want to have two applications (which will always be installed together) share preferences, with one of them being just a service which runs in the background and needs to use the preferences (should own the preferences but only really needs to read them) and the other app being a front-end UI app which needs to be able to write to the preferences file owned by the other app. The service will be doing things in the background (which may be determined by the preferences) and the UI will allow the user to edit the preferences and view some information from the service. However, they will be different packages/apps.

I tried following this tutorial which gave me a pretty good idea of how to have preferences in one app which can be read by another. Essentially, I create a new context through myContext = createPackageContext("com.example.package",Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE); and then call myContext.getSharedPreferences("pref_name", Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE); However, I can't write to the preferences successfully from the outside app - (SharedPreferences.Editor).commit() returns false and I get a warning in logcat about being unable to edit pref_name.xml.bak.

How can I successfully set up my applications so both of them can read and write to the same preferences file (which is stored in the data folder of one of them)?

Answer

Omer Cansizoglu picture Omer Cansizoglu · Jul 15, 2014

It is better to set private mode for the file. App needs to be signed with same set of certificates to share this file.

Set sharedUserId in both apps to be same.

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.hello"
android:versionCode="1"
android:versionName="1.0" 
android:sharedUserId="com.example">
....

Get Context from other package:

mContext = context.createPackageContext(
                        "com.example.otherapp",
                        Context.MODE_PRIVATE);
 mPrefs = mContext.getSharedPreferences("sameFileNameHere", Activity.MODE_PRIVATE);

Get items as usual from SharedPreference. You can access it now.

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