12_Data_Storage_Part_2.pptx
- 1. Data Storage Lecture # 11 Software for Mobile Devices
- 2. Shared Preferences • Shared Preferences are XML files to store private primitive data in key-value pairs. Data Types include Booleans, floats, ints, longs, and strings. • Data saved in SharedPreferences file is accessible throughout the application and persists even after the application closes or across reboots.
- 3. • In order to use shared preferences, you have to call a method getSharedPreferences() that returns a SharedPreference instance pointing to the file that contains the values of preferences. How to use? SharedPreferences sharedpreferences = getSharedPreferences (“AppPreferences”, Context.MODE_PRIVATE); • The first parameter is the key and the second parameter is the MODE. The data saved using SharedPreferences will be available even after your application is killed. The data persists when your application is upgraded!!
- 4. • You can save something in the sharedpreferences by using SharedPreferences.Editor class How to write something in shared preference? sharedpreferences.edit().putString("key", "value").apply(); SharedPreferences sharedpreferences = getSharedPreferences(“AppPreferences”, Context.MODE_PRIVATE); sharedpreferences.edit().putString("key", "value").commit(); Commit() saves data synchronously where as apply() saves data in background (asynchronous). SharedPreferences.Editor editor = sharedpreferences.edit(); editor.putString(Name, n); editor.putString(Phone, ph); editor.putString(Email, e); editor.apply(); OR
- 5. Shared Preference Example 1. SharedPreferences sharedpreferences = getSharedPreferences (“AppPreferences”, Context.MODE_PRIVATE); 1. String value = sharedpreferences.getString("key", ""); 2. String value = sharedpreferences.getInt("key", 0); Second Param is the Value to return if this preference does not exist. Reading from Shared Preference
- 6. Using Sqlite for local data storage SQLite is a opensource SQL database that stores data to a text file on a device. Android comes in with built in SQLite database implementation. SQLite supports all the relational database features. In order to access this database, you don't need to establish any kind of connections for it like JDBC,ODBC e.t.c The main package is android.database.sqlite that contains the classes to manage your own databases Database - Helper class For managing all the operations related to the database , an helper class has been given and is called SQLiteOpenHelper. It automatically manages the creation and update of the database. public class DBHelper extends SQLiteOpenHelper { public DBHelper(){ super(context,DATABASE_NAME,null,1); } public void onCreate(SQLiteDatabase db) { } public void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion) { } } Desktop sql viewer: https://sqlitebrowser.org/ https://stackoverflow.com/questions/17529766/view- contents-of-database-file-in-android-studio
- 7. Creating a Database & Table
- 8. Inserting a Row in Table 1. Inserting data requires getting writable instance (getWriteableDatabase()) on database. 1. ContentValues() is used to define the column name and its data to be stored. Here, we are just setting the note value only ignoring `id` and `timestamp` as these two will be inserted automatically. 1. Every time the database connection has to be closed once you are done with database access. Calling db.close() closes the connection.
- 9. Reading a Row in Table 1. Reading data requires getting readable instance (getReadableDatabase()) on database. 1. Db.query with params table and column names with their values return the data set to cursor. 1. Every time the database connection has to be closed once you are done with database access. Calling db.close() closes the connection. Cursors are what contain the result set of a query made against a database in Android db.close();
- 10. Database Libraries 1. Room The Room persistence library provides an abstraction layer over SQLite to allow for more robust database access while harnessing the full power of SQLite. https://developer.android.com/training/data-storage/room/ 2. Ormlite ORMLite is lighter version of Object Relational Mapping which provide some simple functionality for persisting java objects to SQL databases. It is ORM wrapper over any mobile SQL related DB. http://ormlite.com/android/examples/ http://ormlite.com/ 1. GreenDao greenDAO is an open source Android ORM making development for SQLite databases fun again. It relieves developers from dealing with low-level database requirements while saving development time. http://greenrobot.org/greendao/ Tutorial: https://datarockets.com/blog/android-architecture-migrate-to-room-from-ormlite/ https://www.tldevtech.com/best-android-orm-libraries-to-use/
- 11. Permissions Request permissions at runtime appropriately (in Android 6.0+) 1. Make sure you request permissions at the right time and appropriately educate and inform your users about the need for permission requests. Best practices 1. Educate the user before requesting a permission 2. Always check to see if the permission has been granted 3. Ensure users benefit from allowing a permission immediately 4. Help users undo permission denials Tutorials: https://www.youtube.com/watch?v=iZqDdvhTZj0 https://www.youtube.com/watch?v=C8lUdPVSzDk https://developer.android.com/training/permissions/requesting
- 12. Permissions You should always check for and request permissions at runtime to guard against runtime errors (SecurityException).
- 13. Dangerous Permissions Dangerous permissions cover areas where the app wants data or resources that involve the user's private information, or could potentially affect the user's stored data or the operation of other apps Only dangerous permissions require user agreement. An app must publicize the permissions it requires by including <uses-permission> tags in the app manifest.
- 15. Homework Create your semester project in Android Studio, integrate any database library (Room, ormlite etc) for your project and write a simple read/write/update operation.