Why SharedPreferences use the context?

Question

I try to use SharedPreferences, but I don't understand why we need the context.

If I create a SharedPreferences with the context of my main activity, can I get something with another context?

For example with an intentService class

Thanks

Do not ask this type of Non sense questions here. Search on _Google_ — M D, Apr 30 '15 at 07:28
I'm voting to close this question as off-topic because it is a nonsense question. — Phantômaxx, Apr 30 '15 at 07:32
@David Cesar Santos look at this discussion this might give you some idea http://stackoverflow.com/questions/3572463/what-is-context-in-android — amodkanthe, Apr 30 '15 at 07:40

score 4 · Accepted Answer · answered Apr 30 '15 at 07:41

An IntentService is a subclass of Context (just as are Activity, Application, and many other Android classes). So of course you can create a SharedPreferences from an IntentService. It will see the same SharedPreferences values that any Activity or other Context in your application would see. (That's why it's called shared.) You just have to make sure that you apply() or commit() changes made in the preference's editor in one context for the changes to be seen in other places. This is all covered in the docs.

Thanks for your help! With your answer I understand more about the Context and the SharedPreference. This is very help-full ! — David Cesar Santos, Apr 30 '15 at 08:32

score 2 · Answer 2 · answered Apr 30 '15 at 07:49

The SharedPreferences are read and saved to disk.

Therefore the class needs to know where the app is located - and the only way to know that is thru a Context.

In standard Java there are global (static) objects, so you can do like for example System.getProperty("user.home") to access the user's home directory. That systems isnt maintained in Android - in Android you need to use the Context to get to the home dir of the app

Asif Mujteba · Answer 3 · 2015-04-30T07:54:06.777

Looking at the Android Source Code. You would get to know that Context class internally maintains a static HashMap of shared preferences for quick access:

private static final HashMap<String, SharedPreferencesImpl> sSharedPrefs =
        new HashMap<String, SharedPreferencesImpl>();

So you can get SharedPreferences from any class like Intent Service or Activity etc which extends Context and it will always return the same object if given the same name.

Note: IntentService does extend Context if you trace the chain:

IntentService extends Service
Service extends ContextWrapper
ContextWrapper extends Context

score 1 · Answer 4 · answered Apr 30 '15 at 07:45

Yes, This is non sense question,but anyway. As you know about SharedPreference.It is used to Store private primitive data.

Here,on private data term. This means this data is stored to your application's storage path. Which is data/data/yourpackageName/shared_prefs.

So To access your application's storage, SharePreference needs your active context of any running Activity.

Why SharedPreferences use the context?

4 Answers4