Week 6
TableLayout and SQLite
Objectives
TableLayout, TableRow
Introduction to SQLite
SQLite Java classes in Android
SQLiteOpenHelper
SQLiteDatabase
ContentValues
Cursor
SQLite Database Tutorial
Add/Select/Update/Delete
TABLE LAYOUT
TableLayout and TableRow
Purpose of TableLayout is to organize UI elements in a
table format
Each row in a TableRow is a TableRow instance
TableRow is divided into cells, a cell contains a single
child view
Number of columns is dictated by the row with most
columns
Width of a column is defined by the widest cell in that
column
Columns may be set as shrinkable or stretchable (or
both) so they change in size relative to the parent
TableLayout
A single cell may be configured to span multiple columns
The GUI
The Hierarchical Tree of the
GUI
SQLITE
Introduction
The use of database is an essential
aspect of most applications
Ranging from applications entirely data
driven, to those simply need to store
small amounts of data
Persistent data storage is more
important taking into transient lifecycle
of an Android activity
Android provides SQLite bounded with
Android OS, provides to facilitate
persistent storage
What is SQLite?
SQLite is an embedded, RDBMS
Most RDBMS are standalone server processes run
independently (e.g., Ms. SQL, Oracle, MySQL, etc)
SQLite is referred to as embedded because it is
provided in the form of a library that is linked into
applications.
No standalone DB server running in the background
All DB operations are handled internally within the
application through calls to functions of SQLite Lib
SQLite is written in C, Android SDK provides Java
based wrapper around the DB Interface
This consists of a set of classes to create and manage DB
Trying SQLite on an AVD
Android also provides interactive
environment for issuing SQL commands
from within an adb shell session
connected to a running Android AVD
Once an AVD is running, use Terminal to
connect to the emulator using: adbe
shell
SQLite databases are actually stored in a
database files on the file system of the
Android device
SQLite DB path
By default, the file system path for the
/data/data/<package
name>/databases/<database filename>.db
DB file
is
E.g., in an app with package com.exmple.MyDBApp
/data/data/com.example.MyDBApp/databases/mydatabase.db
ANDROID SQLITE JAVA
CLASSES
Cursor
Provided to access to the results of a database
query
Its use to step through each record then access to
data fields using various methods
Some key methods are:
close(): release resources and close this cursor
getCount(): returns number of rows in the result
moveToFirst(): moves to first row in the result
moveToLast(): moves to the last row in the result
moveToNext(): moves to the next row in the result
move(): moves by a specified offset from current position
get<Type>() returns value of specified <Type>
SQLiteDatabase
It provides the primary interface between the
application code and underlying SQLite
databases
To create/delete databases
To perform SQL based operations on databases
Some key methods of this class are:
insert(): inserts new row into database table
delete(): deletes rows from a database table
query(): performs a query and returns result as
cursor
execSQL(): executes a SQL, does not return result
rawQuery() execute SQL query, returns a cursor
SQLiteOpenHelper
Designed to make it easier to create and update
databases
It must be subclassed within the code of the
application seeking database access
Following call back methods must be implemented
onCreate()
Called when database is created for the first time.
Its passed as argument an SQLiteDatabase object newly
created
This is ideal location to initialize DB like creating table and
inserting initial rows
onUpgrade()
Called when app code contains more recent DB version
Typically happen when app is updated on the device
SQLiteOpenHelper
In addition to the mandatory callback methods
(listed previously), there are some more methods
onOpen(): called when DB is opened
The constructor for the subclass must also be
implemented
Must call the super class, passing through the application
context, the name of the DB and the DB version.
Notable methods of SQLiteOpenHelper class:
getWritableDatabase(): open or creates a DB for reading
and writing. Returns a reference to the DB
getReadableDatabase(): creates or opens a DB for
reading only. Returns a reference to the DB
close(): closes the database
ContentValues
ContentValues is a convenience class
that allows key/value pairs to be
declared
Consisting of table column identifiers
and the values to be stored in each
column
This class is of particular use when
inserting or updating entries in a
database table
SQLITE DATABASE
TUTORIAL
About the DB example
This project is a simple data entry and
retrieval designed to add, query and
delete data
The idea is to allow the tracking of
products
The DB is: productID.db, which contains
a table named products.
Each product contains productid,
productname, productquantity columns.
Productid is PK, and is auto incremented
The classes
Besides the Activity class we will need
A database handler
A subclass of SQLiteOpenHelper
Provides an abstract layer between the DB
and activity
A database model class to represent the
Product
Create a product class
Select appropriate min SDK
Add a Blank Activity
Input Activity Information
The Data Handler
onCreate and onUpgrade
methods
Add/Load Handler Method
Delete Product Handler Method
Update Product Handler
Method
Main Activity GUI
Main Activity Java Code
Add Activity GUI Using
TableLayout
Add Activity Java Code
Test the Add Feature
Load Activity GUI
Layout for single list item
Load Activity Java Code
Test The Load Feature
Delete/Update GUI
Delete Update Activity Java
Delete Update Activity Java
Test The Delete Feature
Update Activity GUI
Update Activity Java
Test Update Activity
Summaries
TableLayout, TableRow
Introduction to SQLite
SQLite Java classes in Android
SQLiteOpenHelper
SQLiteDatabase
ContentValues
Cursor
SQLite Database Tutorial
Add/Select/Update/Delete
