Day 15: Content Provider: Using Contacts API

Android Application Development
Content Provider
Ahsanul Karim
ahsanul.karim@sentinelbd.com
Sentinel Solutions Ltd.
http://www.sentinelbd.com

Application Building Blocks
• UI Component Typically
Corresponding to one screen.
Activity
• Responds to notifications or status
changes. Can wake up your process.
IntentReceiver
• Faceless task that runs in the
background.
Service
• Enable applications to share data.ContentProvider

Android Application Anatomy
Activities
1. Provides User Interface
2. Usually represents a Single Screen
3. Can contain one/more Views
4. Extends the Activity Base class
Services
1. No User Interface
2. Runs in Background
3. Extends the Service Base Class
Application= Set of Android Components
Content Provider
1. Makes application data available
to other apps
2. Data stored in SQLite database
3. Extends the ContentProvider
Base class
Intent/Broadcast Receiver
1. Receives and Reacts to broadcast
Intents
2. No UI but can start an Activity
3. Extends the BroadcastReceiver
Base Class

Android Content Provider
App 1
(Dialer)
App 2
(Messaging)
App 3
(Custom)
App 4
(Custom)
Content Provider 1
Data can be shared over different applications
Content Provider Basics
1. There are no common storage area that all Android application can access.
2. The only way: to share data across applications: Content Provider
3. Content providers store and retrieve data and make it accessible to all
applications.
Content Provider 2

Content Provider Basics (Contd.)
Android ships with a number of content providers for common data types:
1. Audio
2. Video
3. Images
4. Personal contact information etc
Content Provider provides the way to share the data between multiple applications.
For example, contact data is used by multiple applications (Dialer, Messaging etc.)
and must be stored in Content Provider to have common access.
A content provider is a class that implements a standard set of methods to let other
applications store and retrieve the type of data that is handled by that content provider.
Content Provider
data
App 1
App 2

Content Provider Basics (Contd.)
Here are some of Android's most useful built-in content providers, along with a description of
the type of data they're intended to store
Application can perform following operations on content provider -
1. Querying data
2. Modifying records
3. Adding records
4. Deleting records

Querying Data
Content Provider Data Model
Content providers expose their data as a simple table on a database model, where each row
is a record and each column is data of a particular type and meaning.
For example, information about people and their phone numbers might be exposed as follows:
Every record includes a numeric _ID field that uniquely identifies the record within the table.
IDs can be used to match records in related tables — for example, to find a person's phone
number in one table and pictures of that person in another.
A query returns a Cursor object that can move from record to record and column to column
to read the contents of each field. It has specialized methods for reading each type of data.
So, to read a field, you must know what type of data the field contains.

Querying Data
Content Provide: URI
1. Each content provider exposes a public URI that uniquely identifies its data set.
2. A content provider that controls multiple data sets (multiple tables) exposes a
separate URI for each one.
3. All URIs for providers begin with the string "content://".
The content: scheme identifies the data as being controlled by a content provider.
URI samples:
<standard_prefix>://<authority>/<data_path>/<id>
For example, to retrieve all the bookmarks stored by our web browsers (in Android):
content://browser/bookmarks
Similarly, to retrieve all the contacts stored by the Contacts application:
content://contacts/people
To retrieve a particular contact, you can specify the URI with a specific ID:
content://contacts/people/3

Querying Data
So we need three pieces of information to query a content provider:
1. The URI that identifies the provider
2. The names of the data fields you want to receive
3. The data types for those fields
If we are querying a particular record, you also need the ID for that record.
Some more examples:
content://media/internal/images URI return the list of all internal images on the device.
content://contacts/people/ URI return the list of all contact names on the device.
content://contacts/people/45 URI return the single result row, the contact with ID=45.

Querying Data
•Although this is the general form of the query, query URIs are arbitrary and confusing.
•For this android provide list of helper classes in android.provider package that define these
query Strings.
So we do not need to know the actual URI value for different data types.
So it will be easy to query data.
content://media/internal/images/ MediaStore.Images.Media.INTERNAL_CONTENT_URI
content://contacts/people/ Contacts.People.CONTENT_URI
content://contacts/people/45
Uri person = ContentUris.withAppendedId(People.CONTENT_URI, 23);
To query about specific record we have to use same CONTENT_URI and
must append specific ID.
Content Provider: Query
Here is how we can query for data:
Cursor cur = managedQuery(uri, null, null, null);

Querying Data
Content Provider: Query
Here is how we can query for data:
Cursor cur = managedQuery(uri, null, null, null, null);
Parameters:
1. URI
2. The names of the data columns that should be returned. A null value returns all
columns.
3. A filter detailing which rows to return, formatted as an SQL WHERE clause
(excluding the WHERE itself). A null value returns all rows.
4. Selection arguments
5. A sorting order for the rows that are returned, formatted as an SQL ORDER
BY clause (excluding the ORDER BY itself). A null value returns the records in the
default order for the table, which may be unordered.

Querying Data
Content Provider: Query Example
Create a new project:
Project Name: ContentProviderDemo1
Build Target: Android 1.6
Application Name:
ContentProviderDemo1
Package Name:
com.basistraining.cpdemo
Create Activity:
ContentProviderDemoActivity
Min SDK Version: 4
Add READ_CONTACTS permission
Now we make the Activity a
ListActivity to show a list of contacts

Querying Data
Content Provider: Query Example
Now we make the Activity a ListActivity to show a list of contacts:
Now, we’ll add a method to retrieve data from Contacts Content Provider.
The method will return an array of String which will be set as adapter for ListActivity

Querying Data Content Provider: Query Example
Now, we’ll add a method to retrieve data from Contacts Content Provider.
The method will return an array of String which will be set as adapter for ListActivity

Now, we need to show data in list:

Now, We run the app and in emulator we see a black screen as the emulator has no contact
data:
Lets add some contacts using Contacts app

If we run the app again:
What we are doing here???
We are accessing the content provider
Contacts from our application.
Contacts application inserts data into Contact
Content Provider.
App 1
(Contacts)
App 2
(our app)
Contacts Content Provider

Modifying Data Content Provider: Update Example
Let’s add another Activity which will load with selected data and provide us interface to edit:
1. We create Update Activity
2. We modify the main.xml for updating

Let’s get back to ListActivity:
1. To identify which data to be updated we’ll need to pass _ID of the selected Person. So we
Modify the columns
2. We need to save the values in global arrays to pass them as parameter to update screen.
So:

We need to save the values in global arrays to pass them as parameter to update screen.
So:

Now we detect selected person and pass the values to Update screen:
And in the UpdateActivity, we get the values and set them in UI:

Now lets add button functionality of Update
Need the method updateName()

Now lets run the app and we end up with:
WHY????

Now lets run the app and we end up with:
We need to add WRITE_CONTACTS permission

Now follow the steps for testing:
1. Run the app
2. Select a Contact
3. Edit Contact name
4. Go back to main screen
5. Exit app
6. Check whether data is updated from the Contacts app

Practice Exercise
1. Create an Application named “Bookmark Manager”
2. In AVD, browse several sites in browser and bookmark them
3. Read all bookmarks from browser Content Provider and show them in list
4. On selecting an URL go to a new activity and open that link in a webview
Hints
URI: android.provider.Browser.BOOKMARKS_URI
Fields:
1. Browser.BookmarkColumns._ID,
2. Browser.BookmarkColumns.TITLE,
3. Browser.BookmarkColumns.URL

Day 15: Content Provider: Using Contacts API

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Day 15: Content Provider: Using Contacts API