1. Content provider

2. Overview One of the four components of Android
Provides an abstraction of data as a set of tables
Provides an standard interface for other processes to access its data
A client uses ContentResolver to interact with a content provider
A client may need to request permission in Manifest for accessing data

3. General Topics How to interact with a content provider
What content providers are available in Android
Calendar, Contacts, User Dictionary, etc
How to write a content provider

4. Accessing a Provider - Query
Requesting access permission in Manifest
<uses-permission android.permission_READ_USER_DICTIONARY />
Getting an instance of ContentResolver
Context.getContentResolver();
Querying the provide
mCursor = getContentResolver().query(
URI,
projection,
selectionClause,
selectionArgs,
sortOrder);

5. Accessing a Provider - Query
URI
Format: content://authority/path_to_table
Ex., content://user_dictionary/words
Often the provider offers:
UserDictionary.Words.Content_URI constant for URI
Projection
Columns to be returned as an array
Ex., String[] projection = {
UserDictionary.Words._ID,
UserDictionary.Words.WORD};
selectionClause
Selection condition with ? marks for fill-in values
Ex., String selectionClause = UserDicitonary.Words.WORD + “=?”;
selectionArgs
Fill-in values for selectionClause
Ex., String[] selectionArg = { “your word”};
sortOrder
The order of the query result
Ex., String sortOrder = UserDicitonary.Words.WORD + “ ASC”;

6. Accessing a Provider - Insert
Inserting a row to the table
Syntax
URI newUri = getContentResolver().insert(URI, newContentValues);
URI: the content URI of the table. Ex., UserDictionary.Word.Content_URI;
newContentValues: column-value pairs of the new record. Ex.,
ContentValues newValues = new ContentValues();
newValues.put(UserDicitonary.Words.APP_ID, “example.user”);
newValues.put(UserDictionary.Words.LOCALE, "en_US"); newValues.put(UserDictionary.Words.WORD, "insert"); newValues.put(UserDictionary.Words.FREQUENCY, "100");
Note
The operation returns a the Uri of the newly inserted row
Content://user_dictionary/words/<id>

7. Accessing a Provider - Update
Updating rows to the table
Syntax
int rowsUpdated = getContentResolver().update(URI, updateValues,
selectionClause, selectionArgs);
URI: the content URI of the table. Ex., UserDictionary.Word.Content_URI;
updateValues: column-value pairs of the new record. Ex.,
ContentValues updateValues = new ContentValues();
updateValues.put(UserDictionary.Words.LOCALE, "en_US"); updateValues.put(UserDictionary.Words.WORD, "insert")
selectionCause: condition for row selection, ex.,
String selectionClause = UserDictionary.Word.LOCALE + “ LIKE ?”
selectionArgs: values for selectionClause ? marks. Ex.,
String[] selectionArgs = {“en_us”);
Note
The operation returns the number of rows affected by the update

8. Accessing a Provider - Delete
Deleting rows to the table
Syntax
int rowsUpdated = getContentResolver().delete(URI,
selectionClause, selectionArgs);
URI: the content URI of the table. Ex., UserDictionary.Word.Content_Uri;
selectionCause: condition for row selection, ex.,
String selectionClause = UserDictionary.Word.LOCALE + “ LIKE ?”
selectionArgs: values for selectionClause ? marks. Ex.,
String[] selectionArgs = {“en_us”);
Note
The operation returns the number of rows affected by the delete

9. Processing Query Result
Query returns a Cursor
If no row returned, mCursor.getCount()==0;
If error/exception, mCursor == null;
Displaying result in ListView Using SimpleCursorAdapter
Define columns to be selected from Cursor
String[] mFromColumns = { UserDictionary.Words.WORD,
UserDictionary.Words.LOCALE};
Define the view ID’s in the layout
String[] mToFields = { R.id.word, R.id.locale};
Create a SimpleCursorAdapter
mSimpleCursorAdapter = new SimpleCursorAdapter(
getApplicationContext(),
R.layout.listview,
mCursor,
mFromColumns,
mToFields,
0};
Set the adapter to the listview
mListView.setAdapter(mSimpleCursorAdapter );

10. Using Loader with Providers
Activity/Fragment implements LoaderManager.Callbacks interface
In onCreate()/onActivityCreated()
Create a SimpleCursorAdapter
with a null Cursor
Zero (0) as the last parameter of the constructor
void onActivityCreated(Bundle data) {
super.onActivityCreated(data);
mAdapter = new SimpleCursorAdapter(getActivity(),
R.layout.my_layout,
null, // we don’t have data yet, use null
new String[] {Contacts.DISPLAY_NAME},
new int[] {R.id.name},
0}; // since Loader monitors data changes, use 0
// so the adapter would not monitor the data
setListAdapter(mAdapter);
// prepare the loader
getLoaderManager().initLoader(3, null, this); }

11. Using Loader with Providers
In onCreateLoader()
// return a CursorLoader
Loader<Cursor> onCreateLoader(int id, Bundle args) {
Uri baseUri = UserDictionary.Words.Content_URI;
String[] projection = { UserDictionary.Words._ID,
UserDictionary.Words.WORD};
String selectionClause = UserDicitonary.Words.WORD + “=?”;
String[] selectionArgs = { “your word”};
String sortOrder = UserDicitonary.Words.WORD + “ ASC”;
return new CursorLoader(getActivity(), baseUri,
projections,
selectionClause, selectionArgs,
sortOrder); }

12. Using Loader with Providers
In onLoadFinised() and onLoaderReset()
void onLoadFinished(Loader<Cursor> loader, Cursor data) {
// now we have data, put it into the list view
// do not try to close the old cursor,
// android takes care of it
mAdapter.swapCursor(data); }
// if the cursor is about to be closed
void onLoaderReset(Loader<Cursor> loader) {
// called when the cursor is to be closed.
// release the reference to the cursor
mAdapter.swapCursor(null);

13. Android Content Providers
Calendar
Contacts
MediaStore
Telephony
Settings
User Dictionary
Voice Mail

14. Creating a Content Provider
When you need a content provider
If you want your app to provide data to other apps
Steps of building your own provider
Design the storage for your data
Subclass ContentProvider for CRUD operations
Define content URIs
Add other optional features

15. Designing Data Storage
Using SQLite database
SQLite tables map to provider tables nicely
You could use views as provider tables.
Using files
Photos, audio, and videos
Your provider offers a handle to the file
Using network-based data
Use java.net and android.net
Synchronize remote data with local database
Then offer local data as tables or files

16. Designing Data Structures
Primary key
Each table should have a primary key column.
Using BaseColumns._ID makes it easier to integrate with other items such as ListView
If you need to provide large pieces of data
Store data in files
Provide data indirectly through those files
Use Binary Large OBject (BLOB) for data in different sizes and structures.

17. Designing Content URIs
Identifies data in a provider
Consists of authority, path to the table, and row ID
Designing an authority
Each provider has a single authority – android-internal name
To avoid naming conflicts, use your package name
Ex., edu.scranton.mypackagename.provider
Designing a path structure
Append paths to authority
Ex.1, edu.scranton.mypackagename.provider/table1
Ex.2, edu.scranton.mypackagename.provider/table2
Handling content URI ID
Each table has a column _ID as primary key
Ex.1, edu.scranton.mypackagename.provider/table2/324

18. Implementing Required Methods
query(): Cursor
Retrieve data from your provider
Returns a Cursor
Insert(): Uri
Insert a new row to the specified table
Returns a content URI for the new row
Update():int
Update rows with the specified column-value pairs (ContentValues) for rows that satisfy selection clause
Returns the number of rows affected
Delete():int
Delete rows that satisfy the specified selection clause
onCreate()
Android calls it when it starts up the provider.
Initialize your provider. It is not executed until a ContentResolver tries to access the provider
getType()
Return the MIME type corresponding to the content URI>
getSteamType()
Optional – implement when your provider offers files.

19. Implementing Contract Class
A public final class that contains definitions of URIs, column names, MIME types, and other meta-data of the provider
A contract between the provider and its clients
Use JavaDoc to document all the items.
ContactsContract class is an example of such classes.

20. Provider Permissions
List of permissions from coarse-grained to fine-grained permissions
Fine-grained permissions take precedence over ones with coarse-grained
Single read-write provider level permission
Separate read and write provider level permission
Path-level permissions for individual content URI
Temporary permission

21. <Provider> Elements
Authority (android:authority)
Names that identify the entire provider
Provider class name (android:name)
The class that implements ContentProvider
Permissions
Attributes that specify the permissions
andorid:grantUriPermissions: temporary permissions flag
Android:permission: single provider-wide permission
Android:readPermission: provider-wide read permission
Android:writePermission: provider-wide write permission
Startup and control attributes
Determine how and when android starts the provider, the process characteristics of the provider and run-time settings
android:enabled, android:exported, android:initOrder, android:multiProceses, android:syncable.
Informational attributes
An optional icon and label for the provider