Content-Provider chapter five Notes.pptx

notes for content provider

1. Android Application Development Content Provider

2. Application Building Blocks Android Component

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

4. There are no common storage area that all Android application can access. The only way: to share data across applications : Content Provider Content providers store and retrieve data and make it accessible to all applications. Android Content Provider Basics

5. Content Provider Android Component

6. Content Provider Android Component

7. Android ships with a number of content providers for common data types: Audio Video Images Personal contact information etc Android Content Provider Basics 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.

8. 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 Android Content Provider Basics Application can perform following operations on content provider - Querying data Modifying records Adding records Deleting records

9. Querying Data (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 . Android Content Provider

10. Querying Data (Content Provider : URI) Android Content Provider Each content provider exposes a public URI that uniquely identifies its data set. A content provider that controls multiple data sets (multiple tables) exposes a separate URI for each one. 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

11. Querying Data (Content Provider : URI) Android Content Provider So we need three pieces of information to query a content provider: The URI that identifies the provider The names of the data fields you want to receive 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.

12. Querying Data (Content Provider : URI) Android Content Provider 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.

13. Querying Data (Content Provider : URI) Android Content Provider Here is how we can query for data: Cursor cur = managedQuery ( uri , null, null, null, null); Parameters: URI The names of the data columns that should be returned . A null value returns all columns. A filter detailing which rows to return, formatted as an SQL WHERE clause (excluding the WHERE itself). A null value returns all rows. Selection arguments 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. Add READ_CONTACTS permission

14. Querying Data (Content Provider : URI) Android Content Provider Use ContentResolver.query () to retrieve data Method returns a Cursor instance for accessing results Cursor query( Uri uri , // ContentProvider Uri String[] projection // Columns to retrieve String selection // SQL selection pattern String[] selectionArgs // SQL pattern args String sortOrder // Sort order )

15. Querying Data (Code) Android Content Provider public class MainActivity extends Activity { @Override protected void onCreate ( Bundle savedInstanceState ) { super . onCreate ( savedInstanceState ); setContentView ( R . layout . activity_main ); String[] contacts = readContacts (); ArrayAdapter <String> arrayAdapter = new ArrayAdapter <String>(this, android.R.layout.simple_list_item_1, contacts); setListAdapter ( arrayAdapter ); } private void readContacts () { ContentResolver cr = getContentResolver (); Cursor cur = cr . query ( ContactsContract . Contacts . CONTENT_URI , null , null , null , null ); String[] record = new String[ cur.getCount ()]; int a=0; if ( cur . getCount () != ) { while ( cur . moveToNext ()) { String id = cur . getString ( cur . getColumnIndex ( ContactsContract . Contacts . _ID ));

16. Querying Data (Code) Android Content Provider String Name = cur . getString ( cur . getColumnIndex ( ContactsContract . Contacts . DISPLAY_NAME )); if ( Integer . parseInt ( cur . getString ( cur . getColumnIndex ( ContactsContract . Contacts . HAS_PHONE_NUMBER ))) > ) { Cursor pCur = cr . query ( ContactsContract . CommonDataKinds . Phone . CONTENT_URI , null , ContactsContract . CommonDataKinds . Phone . CONTACT _ ID + " = ?" , new String []{ id }, null ); while ( pCur . moveToNext ()) { String Phone = pCur . getString ( pCur . getColumnIndex ( ContactsContract . CommonDataKinds . Phone . NUMBER )) ; Log . i ( MainActivity . this + " " , "Name: " + Name + "Number: " + Phone ); record[ i ] = Name + "\n" + Phone; } i ++; }}} return record;

17. Querying Data (Content Provider: Query Example) Android Content Provider Now, We run the app and in emulator we see a black screen as the emulator has no contact data:

18. Querying Data (Content Provider: Query Example) Android Content Provider If we run the app App 1 (Contacts) App 2 (our app) Contacts Content Provider

19. Querying Data (Deleting Data) Android Content Provider Use ContentResolver.delete () to delete data public final int delete ( Uri url , // content Uri String where, // SQL selection pattern String[] selectionArgs // SQL pattern args )

20. Querying Data (Deleting Data) Android Content Provider private void deleteContact (String name) { ContentResolver resolver = getContentResolver (); String where = ContactsContract.Data. DISPLAY_NAME + " = ? " ; String[] arg = new String[]{name}; ArrayList < ContentProviderOperation > ops = new ArrayList < ContentProviderOperation >(); ops.add ( ContentProviderOperation. newDelete ( ContactsContract.RawContacts. CONTENT_URI ) . withSelection ( where,arg ) .build()); try { resolver.applyBatch ( ContactsContract. AUTHORITY ,ops ); } catch ( RemoteException e){ e.printStackTrace (); } catch ( OperationApplicationException e) { e.printStackTrace (); } }

21. Querying Data (Insert New Contact) Android Content Provider Use ContentResolver . newInsert () to delete data public final int delete ( Uri url , // content Uri ACCOUNT_TYPE , // Account Type e.g [email protected] ACCOUNT_NAME // “ com.what ” ) If ACCOUNT_TYPE = null and ACCOUNT_NAME = null then it’s a local contact