Prepared By : Uday Shah (HOD - IT)
E-Mail : udayshah80@gmail.com
Contact No : 7600044051
Unit
3 : Database connectivity using SQLite
Question : Android Data and Storage UPI
Answer : Android provides several options for you to
save persistent application data. The solution you choose depends on your
specific needs, such as whether the data should be private to your application
or accessible to other applications and the user and how much space your data
requires.
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.
Android
provides a way for you to expose even your private data to other applications with a content provider. A content provider is an
optional component that exposes read/write access to your application data,
subject to whatever restrictions you want to impose.
Question: Explain Intro to Database connectivity using SQLite
·
Android provides a several way to store
user and application data to save information in an application.
·
SQLite is one way for storing user data.
·
SQLite is very light weight database
which comes with android as most of the non travel application also need to save
user settings and some application to manage large amount of information in
file and database. SQLite is an open source database. SQLite support standard
relation.
·
Database feature like SQL syntax
transaction and prepaid statement.
·
The database requires limited memory at
run time. It approximate 250 kilo bytes is default require memory to embedded
database file into the device at runtime.
·
SQLite support the data type like text
integer real in it.
·
Text is like a string in java.
·
Integer is similar to long in a java and
real is similar to double in Java.
·
All other types must be converted into
one of this field before getting saved in the database.
·
SQLite itself does not validate if the
type written to the column are actually of the define type.
·
It means user can write integer into
string column.
·
SQLite is embedded into every android
device.
·
Using and SQLite database in android
does not require a setup procedure or administrator of the database.
·
User have to define SQL statement for
creating and update in the data base after word the database is automatically
manage for user on the android platform to access SQLite database must access
the file system.
·
Which can be store the user data as well
as application data inside the device?
·
If your application create database then
database is by default saved In the directory.
·
According to SQLite architecture the
android database.package must import because it content all necessary class for
working with database.
·
The android.database.SQLite package
content a specific class for SQLite.
·
To create and update a database In your
android application then you have to create a subclass of the SQLite open
helper class.
·
In the constructor of your sub class call
super () method of SQLite open helper class.
·
In this class you need to override
following method to create and update your database. That is
·
1. On create () method
·
2. On update () method
·
Both methods are receiving SQLite
database object as a parameter which is represent in java using the database.
·
SQLite database is base class for
working with SQLite database in android and provide a various method to
manipulate.
·
Database like open database, close
database, update database query to the database.
·
It means SQLite database provides insert
method, update method and delete method.
·
In addition to SQLite database provide execSQL
() method which allow to execute an SQL statement directly.
·
The object content value allows defining
key value in a pair.
·
The key represent table column
identifier and value represent the content for the table record in this column.
·
Content value can be use for insert,
update of database entry.
·
Query can be created using the run query
() method and query () method with the help of SQLite builder class.
·
Row query () method directly accept and
SQL statement as a input query () method provide structure interface for
specific the SQL query.
·
SQLite query builder is a convening
class that helps to built SQL query.
Save
Files
·
Android used a file system that is
similar to disk based file system on other platform.
·
A file object is shied for reading or
writing large amount of data into the device.
·
Android device allow two different
storage area that is internal/external storage.
·
This means that android offer build in
known volatile memory structure for internal storage while some removable
storage used external partition of the storage area.
·
So there are always to storage space and
API behavior is the same weather it is internal removable or not.
·
External storage area is not available
always because user can mount external storage area as a USB storage etc.
·
When user save the file to internal
storage it is automatically store in appropriate directory in a file system
using the following two method.
·
GetfilesDir() method
·
GetcatchDir() method
GetfileDir() method return a file which is
represent in and internal directory while getcacheDir() method return file represent In an internal
directory for your application.
Save to file to external storage
device
· Android application support a limited
storage device inside the hand set so it is compulsory to set external storage
capacity into the device because of the external storage maybe unavailable so
user has to amount an storage to a PC or remove the SD card that is provided
for external storage.
· User can store a file or the media into
external storage state by calling get external storage state () method.
·
There are 2 types of category of your
external storage is
·
Public file
·
Private file
· Public file means a file that should
freely available to other application and to the user.
·
When user uninstalls any application the
file should be remain available for user.
·
E.g. photo capture by your application.
· Private files are the files that is
protected by your application and automatically delete the file when user
uninstall your application.
· Although the file are technically
accessible by the user sometimes it is use for running the application and
specially design for that application.
· Additional resources are download in
your application or a temporary media file is example of private file .
· When the user uninstall your application the
system automatically delete all the file in your application from external
private directory.
Question : Sharing
Data between Applications with Content Providers
- On the Android platform, one application cannot directly access read or write other application's data.
- All persistent data of an app is private to that app.
- Every application has its own id data directory and own protected memory area.
- This means that an app cannot query or manipulate the data of another app.
- However, if you want to enable an app to query or manipulate the data of another app, you need to use the concept of content providers.
Content Provider :
- Content provider is a set of data wrapped up in a custom API to read and write.
- It acts as an interface that allows you to store and retrieve data from a data source.
- And also allows you to share an app’s data with other apps.
- Content providers decouple the app layer from the data layer by abstracting the underlying data source, thereby making apps data-source independent.
- They allow full permission control by monitoring which app components or users should have access to the data making data sharing easy.
- As a result, any app with appropriate permissions can add, remove, update, and retrieve data of another app including the data in some native Android databases.
There are 2
types of Content Providers:
Custom
content providers: These are
created by the developer to suit the requirements of an app.
Native
content providers: These
provide access to built-in databases, such as contact manager, media player,
and other native databases. You need to grant the required permissions to your
app before using native content providers.
Eg: The
WhatsApp app sharing mobile contacts data and Media store-Allows other
applications to access, store media files.
Above
diagram shows how content provider works. Application 2 stores its data in its
own database and provides a provider. Application 1 communicates with the
provider to access Application 2's data.
Content
Provider uses a special URI starting with content:// will
be assigned to each content providers and that will be recognized across
applications.
Creating a
Content Provider :
To create a
content provider we need to
Create sub class for
ContentProvider.
Define content URI
Implement all the unimplemented
methods. insert(), update(), query(), delete(), getType().
Declare the content provider in AndroidManifest.xmlhttps://myshopprime.com/uday.shah3/shop
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