Android Shared Preferences.

Shared Preferences are used in Android to store data. These data can be used in appropriate places in the application from reading them.

The shared preferences allows us to manage a session. Session is useful when need to store user data globally throughout the application. This can be done storing the data in shared preferences.

Shared Preferences is an API which includes in Android SDK to store and retrieve application preferences. Shared Preferences are simply sets of data in key value pair that stored persistently. Furthermore if the application stop or turn off the device will not clear the data stored in  shared preferences. Shared Preferences available at the Activity level or shared across all Activity in application package.

Shared Preferences are used in android to store some data persistently so when you need to store few amount of data then you can use Shared Preferences instead of SQLite.

But shared preference is not a solution to keep complex relational data.

The following basic information will be  needed when you use the Shared Preferences in your application.

Store Data in Shared Preferences.

All the primitive data types like boolean, floats, int, longs, and strings can store in Shared Preferences using following methods.

editor.putBoolean("key_name", true); // Storing boolean - true/false

editor.putString("key_name", "string value"); // Storing string

editor.putInt("key_name", "int value"); // Storing integer

editor.putFloat("key_name", "float value"); // Storing float

editor.putLong("key_name", "long value"); // Storing long

Retrieve data from Shared Preferences.

All the primitive data types like boolean, floats, int, longs, and strings can retrieve from Shared Preferences using following methods.

// returns stored preference value

// If value is not present return second param value - In this case null

pref.getString("key_name", null); // getting String

pref.getInt("key_name", null); // getting Integer

pref.getFloat("key_name", null); // getting Float

pref.getLong("key_name", null); // getting Long

pref.getBoolean("key_name", null); // getting boolean

Delete data from Shared Preferences

If you want to delete from shared preferences you can call remove(“key_name”) to delete that particular value. If you want to delete all the data, call clear().

Eg :- editor.remove(“email”) – this will remove the key email from your Shared Preference.

Editor.clear() – this will clear all the data from shared preferences.

 Save Changes in Shared Preferences

You can save all the changes in Shared Preferences using commit().

The following example method implemented to show how to store data in the Shared Preferences.

public static void saveGlobalStringPreferences(final Activity activity,

                                    final String key, final String value) {

                        SharedPreferences sp = PreferenceManager

                                                .getDefaultSharedPreferences(activity.getApplicationContext());

                        Editor editor = sp.edit();

                        editor.putString(key, value);

                        editor.commit();

}

As you can see above, after storing a particular data in shared preferences need to commit it to save the changes successfully.

The following example method implemented to show how to retrieve data from the Shared Preferences.

public static String readGlobalStringPreferences(final Activity activity,

                                    final String key, final String defaultValue) {

                        SharedPreferences sp = PreferenceManager

                                    .getDefaultSharedPreferences(activity.getApplicationContext());

                        return sp.getString(key, defaultValue);

}

The following example method implemented to show how to delete data from the Shared Preferences.

public static void removeGlobalPreferences(final Activity activity,

                                    final String key) {

                        SharedPreferences sp = PreferenceManager

                                    .getDefaultSharedPreferences(activity.getApplicationContext());

                        Editor editor = sp.edit();

                        editor.remove(key).commit();

}

As you can see above, after removing a particular data from shared preferences need to commit it for successfully deletion.

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