共享首选项始终返回默认值

Question

Here is code I am Using to create and store value in Preference. outgoing is String variable.

SharedPreferences sp = getSharedPreferences(outgoing, Activity.MODE_PRIVATE);
SharedPreferences.Editor editor = sp.edit();                
editor.putString("PhoneNo","Hi");
editor.commit();

Here is the code to get value from SharedPreference.

SharedPreferences sp 
=getSharedPreferences(outgoing,Activity.MODE_PRIVATE);
String calln = sp.getString("PhoneNo","0");
Toast.makeText(mContext, "SHARED"+calln,Toast.LENGTH_LONG).show();

Answer 1

You should probably call the getSharedPreferences on the context from which you are accessing them.

Source

Therefore, depending on how you can access your context, if you pass it to some other activity or in an asynchronous task, here are some examples of usage:

this.getSharedPreferences(outgoing, Activity.MODE_PRIVATE);

context.getSharedPreferences(outgoing, Activity.MODE_PRIVATE);

getApplicationContext().getSharedPreferences(outgoing, Activity.MODE_PRIVATE);

Also, one way you can test your stuff is to use a listener when SharedPreferences get changed:

onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key)

Called when a shared preference is changed, added, or removed.

here is how to do that

You can also use the Preference Manager to obtain the SharedPreferences :

PreferenceManager.getSharedPreferences(YOUR_CONTEXT).getString(
                    "PhoneNo", "0");

Or to store them:

PreferenceManager.getSharedPreferences(YOUR_CONTEXT).edit().putString(
                    "PhoneNo", "Hi").commit();

Answer 2

改变这种Activity.MODE_PRIVATE这个Activity.MODE_MULTI_PROCESS ，问题是存储价值和访问期间，值可能是由于不同的上下文。

Answer 3

When putting values, try changing this:

SharedPreferences sp = getSharedPreferences(outgoing, Activity.MODE_PRIVATE);

to this:

SharedPreferences sp = getApplicationContext().getSharedPreferences(outgoing, Activity.MODE_PRIVATE);

Same when getting values - don't forget to add getApplicationContext() in your call to SharedPreferences

EDIT: Check that your "outgoing" String is the exact same in both Activities

Answer 4

The most likely reason that Shared Preference always returns the default value is that you saved the value in one preference file and then tried to retrieve it in another preference file. This can happen if you do call getPreferences() from different Activities, because getPreferences() creates a different preference file based on the activity it is created in.

Solution

The easiest solution is to always get your shared preferences like this:

SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(context);

This will use a single preference file for the entire app.

Alternate solution

If for some reason you need to use different preference files, then you can do

final static String PREF_FILE_1 = "pref_file_1";
...
SharedPreferences sharedPref = context.getSharedPreferences(PREF_FILE_1, Context.MODE_PRIVATE);

Just make sure you always use the right file name for the preferences you are trying to save and retrieve.

Local preferences

If you really only need a preference for a specific Activity, then you can use getPreferences(Context.MODE_PRIVATE) . Just don't expect to be able to retrieve the values from another Activity in the same way.

See also

• This answer describes the differences between the various ways of obtaining SharedPreferences .
• Difference between getDefaultSharedPreferences and getSharedPreferences
• Mess with the shared preferences of android - which function to use?