SQLite DB Storing Data in Android RAVI GAURAV PANDEY 1

RAVI GAURAV PANDEY 1

SQLite DBStoring Data in Android


Storing Data on Android PlatformFour ways of storing data

Preferences SQLite Database Files Network

Preferences –

Basically used for storing user preferences for a single application or across applications for a mobile. This is typically name-value pairs accessible to the context.

Databases –

Android supports creating of databases based on SQLite db. Each database is private to the applications that creates it

Files –

Files can be directly stored on the mobile or on to an extended storage medium. By default other applications cannot access it.

Network –

Data can be stored and retrieved from the network too depending on the availability.

If an application wants to store and retrieve data for its own use, without having to share the data across applications, it can access the SQLite DB directly. There is no need of a content provider.


SQLite DB Operations

Create a database (typically a one time activity)

Create a table (typically a one time activity)

Insert values into the table

Retrieve the values from the table

Display the retrieved values as a List view

Delete all the records from the table before closing the connection to the database


SQLite DataTypes

This is quite different than the normal SQL data types so please read:

Storage Class Description

NULL The value is a NULL value.

INTEGER

The value is a signed integer, stored in 1, 2, 3, 4, 6, or 8 bytes depending on the magnitude of the value.

REALThe value is a floating point value, stored as an 8-byte IEEE floating point number.

TEXTThe value is a text string, stored using the database encoding (UTF-8, UTF-16BE or UTF-16LE)

BLOBThe value is a blob of data, stored exactly as it was input.


Affinity Types

SQLite supports the concept of type affinity on columns. Any column can still store any type of data but the preferred storage class for a column is called its affinity. Each table column in an SQLite3 database is assigned one of the following type affinitiesAffinity Description

TEXTThis column stores all data using storage classes NULL, TEXT or BLOB.

NUMERICThis column may contain values using all five storage classes.

INTEGERBehaves the same as a column with NUMERIC affinity with an exception in a CAST expression.

REAL

Behaves like a column with NUMERIC affinity except that it forces integer values into floating point representation

NONE

A column with affinity NONE does not prefer one storage class over another and no attempt is made to coerce data from one storage class into another.


SQLite Packages & Classes(android.database.sqli

te)

The “sqlite” Contains the SQLite database management classes that an application would use to manage its own private database.

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.


android.database.sqlite.SQLiteDatabase

Contains the methods for: creating, opening, closing, inserting, updating, deleting and quering an SQLite database

These methods are similar to JDBC but more method oriented than what we see with JDBC (remember there is not a RDBMS server running)


1. Creating a Database

SQLiteDatabase sampleDB = this.openOrCreateDatabase(SAMPLE_DB_NAME, MODE_PRIVATE, null);

This opens a database defined in the constant SAMPLE_DB_NAME, if it already exists. Else it creates a database and opens it. The second parameter is operating mode : MODE_PRIVATE meaning it is accessible to only this context. The other modes are and MODE_WORLD_WRITABLE. MODE_WORLD_READABLE


Database Properties

Important database configuration options include: version, locale, and thread-safe locking.

import java.util.Locale;

myDatabase.setVersion(1);

myDatabase.setLockingEnabled(true);

myDatabase.SetLocale(Locale.getDefault());


2. Creating a Table

sampleDB.execSQL("CREATE TABLE IF NOT EXISTS " +

SAMPLE_TABLE_NAME +

" (LastName VARCHAR, FirstName VARCHAR," +

" Country VARCHAR, Age INT(3));");


3. Inserting Values

sampleDB.execSQL("INSERT INTO " +

SAMPLE_TABLE_NAME +

" Values (‘Tom',‘Patterson',‘UK',28);");


4. Retrieve a Value

Cursor c = sampleDB.rawQuery("SELECT FirstName, Age FROM " +

SAMPLE_TABLE_NAME +

" where Age > 10 LIMIT 5", null);

if (c != null ) {

if (c.moveToFirst()) {

do {

String firstName = c.getString(c.getColumnIndex("FirstName"));

int age = c.getInt(c.getColumnIndex("Age"));

results.add("" + firstName + ",Age: " + age);

}while (c.moveToNext());

}

}


5. Display the values as List

this.setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,results));

The statement displays it as a list as the class extends a ListActivity.


6. Deleting the values

finally {

if (sampleDB != null)

sampleDB.execSQL("DELETE FROM " + SAMPLE_TABLE_NAME);

sampleDB.close();

}


QUESTIONS?

Documents

SQLite DB Storing Data in Android RAVI GAURAV PANDEY 1