Difference between getDefaultSharedPreferences and getSharedPreferences

Question

What is the difference between getDefaultSharedPreferences and getSharedPreferences in Android? Can anyone please explain?

Solution 1

getDefaultSharedPreferences will use a default name like "com.example.something_preferences", but getSharedPreferences will require a name.

getDefaultSharedPreferences in fact uses Context.getSharedPreferences (below is directly from the Android source):

public static SharedPreferences getDefaultSharedPreferences(Context context) {
    return context.getSharedPreferences(getDefaultSharedPreferencesName(context),
        getDefaultSharedPreferencesMode());
}

private static String getDefaultSharedPreferencesName(Context context) {
    return context.getPackageName() + "_preferences";
}

private static int getDefaultSharedPreferencesMode() {
    return Context.MODE_PRIVATE;
}

Solution 2

Let's review the basic points of difference:

1. getDefaultSharedPreferences() uses a default preference-file name. This default is set per application, so all activities in the same app context can access it easily as in the following example:

   SharedPreferences spref = PreferenceManager.getDefaultSharedPreferences(this);
   if (spref.contains("email")) {
        String sEmailAddr = spref.getString("email", "");
   }
   

   The preferences are usually stored at /data/data/com.package.name/shared_prefs/com.package.name_preferences.xml.

2. The alternative method - getSharedPreferences(name,mode) requires to indicate a specific preference (file) name and an operation mode (e.g. private, world_readable, etc.)

As mentioned by copolii, the result is the same, but the first option is simpler and lacks the flexibility to split to multiple preference files, that is offered by the second option of getSharedPreferences(). Sharing the preferences between apps using a MODE_WORLD_READABLE operation indicator is also something possible using getSharedPreferences(), but is rarely used.

IMHO, getDefaultSharedPreferences() can be safely used without going into the confusion of multiple preference file names that are prone to typos and confusion, unless you want that different modules in your app will use different preference files. Normally this is not needed. If an app needs to save a lot of parameters, probably using external database will be better as it offers also better data protection.

If someone knows of a good reason to regularly use getSharedPreferences() and not getDefaultSharedPreferences(), please let me know by commenting here.

Solution 3

I know this post is a bit old, but since 24.0.1 of the v7 support library you can retrieve the default preferences by context anywhere using

// context might be an application context, activity, ..
// so if you want to get your apps defaults, pass an activity context
PreferenceManager.getDefaultSharedPreferences(context)

See https://developer.android.com/reference/android/support/v7/preference/PreferenceManager#getdefaultsharedpreferences

Solution 4

There's a 3rd function as well:

public SharedPreferences Activity.getPreferences(int mode) {}

See my question and answer here: Mess with the shared preferences of android - which function to use?

Solution 5

Be aware that using default shared preferences is NOT the same as using shared preferences with your package name:

context.getSharedPreferences(getPackageName(), MODE_PRIVATE);

=> Name of shared preferences: "com.my.packagename"

PreferenceManager.getDefaultSharedPreferences(context);

=> Name of shared preferences: "com.my.packagename_preferences"

View more solutions

Comments

[LarsH]

An almost-too-obvious difference is that one is static and one is not. But it doesn't really matter, since you need a Context instance in order to call either one.

[Martin]

To bad getDefaultSharedPreferencesName is not public as the name is needed for the backup / restore framework.

[Kostadin]

My reason is: stackoverflow.com/questions/10786172/…

[Dr.jacky]

What about stackoverflow.com/questions/10786172/… ?

[Dr.jacky]

And how to listen to preference change , in getSharedPreferences mode that use custom name for preference ? (not use default name like getSharedPreferences "com.example.something_preferences")

[Dr.jacky]

And how to listen to preference change , in getSharedPreferences mode that use custom name for preference ? (not use default name like getSharedPreferences "com.example.something_preferences")

[Mr_and_Mrs_D]

Could you please add a link to the source ?

[copolii]

@Mr_and_Mrs_D it's easier to look it up. If I add a link it would be to a specific API version, which may or may not be what you're looking for.

[Zapnologica]

so they are exactly the same? the one is just a helper to make calling it easier?

[tarn]

This is a wrapper for getSharedPreferences() from the Activity source code: public SharedPreferences getPreferences(int mode) { return getSharedPreferences(getLocalClassName(), mode); }

[copolii]

@Zapnologica Correct.

[Mahmoud]

@Martin the method getDefaultSharedPreferencesName(..) became public starting from API 24.

[Alex Weavers]

Dr.jacky I'd say you would wrap up your preferences in some sort of Session-like object: class Session { prefs = getSharedPreferences() ... } and then use getters and setters for the things you want to monitor. When the setters are called, you can trigger events in the setter logic.

[Kevin]

PreferenceManager is being deprecated in Android Q. You can still use the context.getSharedPreferences way of things though. Changed this call to context.getSharedPreferences("${packageName}_preferences", MODE_PRIVATE)

[FutureShocked]

It looks like PreferenceManager is being deprecated in that it is just being moved to Androix. developer.android.com/reference/androidx/preference/…