Android Training (Storing & Shared Preferences)
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The document discusses various options for storing data in Android applications, including shared preferences, internal storage, external storage, SQLite databases, and network connections. It provides details on how to use shared preferences to store private primitive data in key-value pairs, including initialization, storing and retrieving data, and clearing data. It also covers using internal storage to privately save files on the device memory.
Android Training (Storing & Shared Preferences)
- 1. Android Data Storage Android Training By Khaled Anaqwa
- 2. Your data storage options are the following: Shared Preferences Store private primitive data in key-value pairs. Internal Storage Store private data on the device memory. External Storage Store public data on the shared external storage. SQLite Databases Store structured data in a private database. Network Connection Store data on the web with your own network server.
- 3. SharedPreferences The SharedPreferences class provides a general framework that allows you to save and retrieve persistent key-value pairs of primitive data types. This data will persist across user sessions (even if your application is killed).
- 4. To work with shared preferences you need to Initialization Storing Data Commit changes Retrieving Data Clearing / Deleting Data
- 5. Initialization Application shared preferences can be fetched using getSharedPreferences() method. You also need an editor to edit and save the changes in shared preferences. SharedPreferences pref = getApplicationContext().getSharedPreferences(”FileName", 0); // 0 - for private mode Editor editor = pref.edit();
- 6. Application shared preferences can be fetched using getSharedPreferences() - Use this if you need multiple preferences files identified by name, which you specify with the first parameter. getPreferences() - Use this if you need only one preferences file for your Activity. Because this will be the only preferences file for your Activity, you don't supply a name.
- 7. Storing Data You can save data into shared preferences using editor. All the primitive data types like booleans, floats, ints, longs, and strings are supported. You need to put data as Key with Value. 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
- 8. Commit changes Call editor.commit() in order to save changes to shared preferences.. like editor.commit();
- 9. Retrieving Data Data can be retrived from saved preferences by calling getString() (For string) method. Remember this method should be called on Shared Preferences not on Editor. // returns stored preference value // If value is not present return default 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
- 10. Clearing / Deleting Data 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(). editor.remove("name"); // will delete key name editor.remove("email"); // will delete key email editor.commit(); // commit changes; editor.clear(); //clear all the data from shared preferences editor.commit(); // commit changes
- 11. Task Create Settings with ShaerdPresferance General Settings Language selection Text Size Email Textcolor System Settings Enable Notifications use Wifi About
- 12. Using the Internal Storage You can save files directly on the device's internal storage. By default, files saved to the internal storage are private to your application and other applications cannot access them. When the user uninstalls your application, these files are removed.
- 13. To create and write a private file to the internal storage: Call openFileOutput() with the name of the file and the operating mode. This returns a FileOutputStream. Write to the file with write(). Close the stream with close().
- 14. String FILENAME = "hello_file"; String string = "hello world!"; FileOutputStream fos = openFileOutput(FILENAME,Context.MODE_PRIVATE); fos.write(string.getBytes()); fos.close();
- 15. To read a file from internal storage: Call openFileInput() and pass it the name of the file to read. This returns a FileInputStream. Read bytes from the file with read(). Then close the stream with close().
- 16. RAW Files If you want to save a static file in your application at compile time, save the file in your project res/raw/ directory. You can open it with openRawResource(), passing the R.raw.<filename> resource ID. This method returns an InputStream that you can use to read the file (but you cannot write to the original file).
- 17. Cache Files: If you'd like to cache some data, rather than store it persistently, you should use getCacheDir() to open a File that represents the internal directory where your application should save temporary cache files.
- 18. PreferenceActivity This is the base class for an activity to show a hierarchy of preferences to the user. this functionality should now be found in the new PreferenceFragment class. using PreferenceActivity in its old mode, the documentation there applies to the deprecated APIs here.