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Data Storage In Android

The document discusses various data storage options in Android including shared preferences, internal storage, external storage, SQLite databases, and network/cloud storage. It provides details on how to use shared preferences to store private data in key-value pairs, how to read and write files to internal and external storage, how to create and manage SQLite databases to store structured data, and lists some popular cloud storage providers.

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BY: AKASH UGALE Data Sores in Android Operating System
Data Storage In Android 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.
Shared Preferences Useful for storing and retrieving primitive data in key value pairs. Lightweight usage, such as saving application settings. Typical usage of SharedPreferences is for saving application such as username and password, auto login flag, remember-user flag etc.
Shared Preferences Contd….. The shared preferences information is stored in an XML file on the device  Typically in/data/data/<Your Application’s package name>/shared_prefs SharedPreferences can be associated with the entire application, or to a specific activity. Use the getSharedPrefernces() method to get access to the preferences
Shared Preferences Contd….. Example:  SharedPrefernces prefs = this.getSharedPrefernces(‘myPrefs, MODE_PRIVATE’) If the preferences XML file exist, it is opened, otherwise it is created. To Control access permission to the file:  MODE_PRIVATE:private only to the application  MODE_WORLD_READABLE:all application can read XML file  MODE_WORLD_WRITABLE:all application can write XML file
Shared Preferences Contd….. To add Shared preferences, first an editor object is needed  Editor prefsEditor = prefs.edit(); Then,use the put() method to add the key-value pairs  prefsEditor.putString(“username”,”D-Link”);  prefsEditor.putString(“password”,”vlsi#1@2”);  prefsEditor.putint(“times-login”,1);  prefsEditor.commit();
Shared Preferences Contd….. To retrieve shared preferences data:  String username = prefsEditor.getString(“username”.” ”);  String password = prefsEditor.getString(“password”.” ”); If you are using SharedPrefernces for specific activity, then use getPreferences() method  No need to specify the name of the preferences file
Example
Internal Storage Android can save files directly to the device internal storage. These files are private to the application and will be removed if you uninstall the application. We can create a file using openFileOutput() with parameter as file name and the operating mode. Generally not recommended to use files.
Internal Storage Contd…. Similarly, we can open the file using openFileInput() passing the parameter as the filename with extension. File are use to store large amount of data Use I/O interfaces provided by java.io.* libraries to read/write files. Only local files can be accessed.
File Operation(Read) Use context.openFileInput(string name) to open a private input file stream related to a program. Throw FileNotFoundException when file does not exist. Syntax:- fileinputStram.in=this.openfileinput(“xyz.txt”) . . . . . In.close()://Close input stream
File Operation (Write) Use context.openFileOutput(string name,int mode ) to open a private output file stream related to a program. The file will be created if it does not exist. Output stream can be opened in append mode, which means new data will be appended to end of the file. String mystring=“Hello World”
File Operation (write) Contd…. Syntax:- FileOutputStream outfile = this.openFileOutput(“myfile.txt”,MODE_APPEND) //Open and Write in”myfile.txt”,using append mode. Outfile.write(mystring.getBytes()); Outfile.close();//close output stream
External Storage Every Android-compatible device supports a shared “external storage” that you can use to save files  Removable storage media (such as an SD card)  Internal (non-removable) storage File saved to the external storage are world readable and can be modified by the user when they enable USB mass storage to transfer files on computer. These files are private to the application and will be removed when the application is uninstalled.
External Storage Continue Must check whether external storage is available first by calling getExternalStorageState()  Also check whether it allows read/write before reading/writing on it getExternalFilesDir() takes a parameter such as DIRECTORY_MUSIC,DIRECTORY_RINGTONE etc,to open specific type of subdirectories. For public shared directories,use getExternalStoragePublicDirectory()
External Storage Contd….. For cache files,use getExternalCacheDir() All these are applicable for API level 8 or above For API level 7 or below ,use the method;  getExternalStorageDirectory()  Private files stored in//Android/data/<package_name>/files/  Cache files stored in//Android/data/<package_name>/cache/
Example
SQLite Databases android.database.sqlite Contains the SQLite database management classes that an application would use to manage its own private database. android.database.sqlite.SQLiteDatabase Contains the methods for: creating, opening, closing, inserting, updating, deleting and quering an SQLite database.
android.database.sqlite - Classes  SQLiteCloseable - An object created from a SQLiteDatabase that can be closed.  SQLiteCursor - A Cursor implementation that exposes results from a query on a SQLiteDatabase.  SQLiteDatabase - Exposes methods to manage a SQLite database.  SQLiteOpenHelper - A helper class to manage database creation and version management.  SQLiteProgram - A base class for compiled SQLite programs.  SQLiteQuery - A SQLite program that represents a query that reads the resulting rows into a CursorWindow.  SQLiteQueryBuilder - a convenience class that helps build SQL queries to be sent to SQLiteDatabase objects.  SQLiteStatement - A pre-compiled statement against a SQLiteDatabase that can be reused.
OpenOrCreateDatabase This method will open an existing database or create one in the application data area  import android.database.sqlite.SQLiteDatabase; SQLiteDatabase myDatabase; myDatabase = openOrCreateDatabase ("my_sqlite_database.db" , SQLiteDatabase.CREATE_IF_NECESSARY , null);
Creating Tables Create a static string containing the SQLite CREATE statement, use the execSQL( ) method to execute it.  String createAuthor = "CREAT TABLE authors ( id INTEGER PRIMARY KEY AUTOINCREMENT, fname TEXT, lname TEXT); myDatabase.execSQL(createAuthor);
insert( ), delete( ) long insert(String table, String nullColumnHack, ContentValues values) import android.content.ContentValues; ContentValues values = new ContentValues( ); values.put("firstname" , "J.K."); values.put("lastname" , "Rowling"); long newAuthorID = myDatabase.insert("tbl_authors" , "" , values); int delete(String table, String whereClause, String[] whereArgs) public void deleteBook(Integer bookId) { myDatabase.delete("tbl_books" , "id=?" , new String[ ] { bookId.toString( ) } ) ; }
Update() int update(String table, ContentValues values, String whereClause, String[ ] whereArgs) public void updateBookTitle(Integer bookId, String newTitle) { ContentValues values = new ContentValues(); values.put("title" , newTitle); myDatabase.update("tbl_books" , values , "id=?" , new String[ ] {bookId.toString() } ); }
SQLite Storage
Content Provider
Cloud Storage  Online file storage centres or cloud storage providers allow you to safely upload your files to the Internet.
Cloud Storage Contd….. There are various providers of cloud storage Examples: Apple iCloud(Gives 5GB of free storage ) Dropbox(Gives 2GB of free storage ) Google Drive(Gives 15GB of free storage ) Amazon Cloud Drive(Gives 5GB of free storage Microsoft SkyDrive(Gives 7GB of free storage )
Example
Data Storage In Android