Saving User Settings in Android: Insights into Shared Preferences

Discover in our latest blog post how to efficiently save and restore user settings in Android applications using Shared Preferences. From initialization to retrieving saved data - we guide you through the process and show you how easy it is to manage data in the form of key-value pairs.

Overview of Android Shared Preferences

Shared Preferences allows activities and applications to store settings in the form of key-value pairs similar to a map, which persist even when the user closes the application. Android stores the Shared Preferences settings as an XML file in the shared_prefs folder under the DATA/data/{application package} directory. The DATA folder can be obtained by calling Environment.getDataDirectory(). SharedPreferences are application-specific, meaning the data will be lost if any of the following actions are taken:

• When uninstalling the application
• When deleting application data (via settings)

As the name suggests, the main purpose is to store user-specific configuration details, such as user preferences to keep the user logged in to the application. To access the settings, we have three APIs to choose from:

• getPreferences(): used within your activity to retrieve activity-specific settings
• getSharedPreferences(): used within your activity (or other application contexts) to retrieve application-wide settings
• getDefaultSharedPreferences(): used on the PreferenceManager to retrieve the shared preferences that work in line with the entire Android preference framework

In this tutorial, we will be using getSharedPreferences(). The method is defined as follows: getSharedPreferences(String PREFS_NAME, int mode) PREFS_NAME is the name of the file. Mode is the operating mode. The following operating modes are applicable:

• MODE_PRIVATE: the default mode in which the created file is accessible only by the calling application
• MODE_WORLD_READABLE: Creating world-readable files is very dangerous and can cause security holes in applications
• MODE_WORLD_WRITEABLE: Creating world-writable files is very dangerous and can cause security holes in applications
• MODE_MULTI_PROCESS: This method checks for changes to the settings even if the shared preference instance has already been loaded
• MODE_APPEND: This appends new settings to the existing ones
• MODE_ENABLE_WRITE_AHEAD_LOGGING: Database open flag. When set, enables write-ahead logging by default

Initialization

We need an editor to edit and save changes in the Shared Preferences. The following code can be used to obtain the Shared Preferences:

SharedPreferences pref = getApplicationContext().getSharedPreferences("MyPref", 0); // 0 - for private mode
SharedPreferences.Editor editor = pref.edit();

Saving Data

editor.commit() is used to save changes in the Shared Preferences. An example of saving data:

editor.putBoolean("key_name", true); // Saving Boolean - true/false
editor.putString("key_name", "String value"); // Saving String
editor.putInt("key_name", 123); // Saving Integer
editor.putFloat("key_name", 3.14f); // Saving Float
editor.putLong("key_name", 123456789L); // Saving Long

editor.commit(); // Confirming changes

Retrieving Data

Data can be retrieved from the saved settings using getString() as follows:

pref.getString("key_name", null); // Retrieving String
pref.getInt("key_name", -1); // Retrieving Integer
pref.getFloat("key_name", -1.0f); // Retrieving Float
pref.getLong("key_name", -1L); // Retrieving Long
pref.getBoolean("key_name", false); // Retrieving Boolean

Deleting Data

remove("key_name") is used to delete a specific value. clear() is used to remove all data.

editor.remove("name"); // will delete the key "name"
editor.remove("email"); // will delete the key "email"

editor.commit(); // Confirming changes
editor.clear();
editor.commit(); // Confirming changes

Project Structure

The project structure includes the activity (MainActivity.java) and the layout (activity_main.xml). The MainActivity.java file is used to save and retrieve data, while the activity_main.xml layout contains two EditText views to save and display names and emails. With this knowledge, you can save and restore user settings and other data in your Android application. Happy coding!

That's it for this tutorial. Thank you for reading!