1. Content Providers

2. Objectives What are content providers?
How to use a content provider in Android
How to create your own content provider

3. Motivation
Different ways to persist data, e.g., shared preferences, files, and SQLite
but, accessible only by the package that created it
Various persistent data from Android, e.g.
Browser: browser bookmarks, borwser history, etc.
CallLog: missed calls, call details, etc.
Contacts: contact details
MediaStore: audio, video, and images
Setting: device's settings and preferences
Q: How to share these data across packages and applications in a uniform way?

4. Content Provider: Sharing Data In Android
Provides a consistent, uniform programming interface for sharing data
Can be thought of as a data store, e.g., query, edit, add, and delete
But unlike database, can be stored in many different ways
Built-in vs user-defined

5. What API Or Facility? Naming a data store (URI)
Querying a data store (query, Cursor)
Table view of data store
Inserting a new record (insert)
Deleting an existing record (delete)
Updating an existing record (update)

6. Querying Content Providers
Use a query string in the form of URI
content://<authority>/<data_path>/<id>
<authority>: name of content provider, e.g.,
contacts for built-in Contacts content provider
edu.utep.cs.cs4390.grade for user-defined
<data_path>: specifies the kind of data requested, e.g.,
content://contacts/people
<id>: specifies the specific record requested, e.g.,
content://contacts/people/2 <-- second record

7. Examples
content://media/internal/images content://media/external/images content://call_log/calls content://browser/bookmarks

8. Querying Use the query method of ContentResolver
Cursor query(URI uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
uri: content to retrieve
projection: list of columns to return; null for all columns
selection: filter declaring which rows to return, formatted as
an SQL WHERE clause; null for all rows
Use SQL operators: =, <>, >, <, >=, <=, between, like, in
selectionArgs: args for "?s" in selection
sortOrder: order of rows, formatted as an SQL ORDER BY clause
e.g., “name asc” and “name desc”

9. Example Uri allContacts = Uri.parse("content://contacts/people");
Cursor c = getContentsResolver().query(allContacts, null, null, null, null);
if (c.moveToFirst()) {
do {
String id = c.getString(c.getColumnIndex(
ContactsContract.Contacts._ID));
String name = c.getString(c.getColumnIndex(
ContactsContract.Contacts.DISPLAY_NAME));
...use id and name ....
} while (c.moveToNext()); }
*Note that ContentsResolver.query is a synchronous call.
*Can use a CursorAdapter class such as SimpleCursorAdapter to display
results in an AdapterView such as ListView.

10. Cursor Class
Interface providing random read-write access to the result set returned by a database query
int getColumnCount(): total number of columns
int getColumnIndex(String): zero-based index for the column name
String getColumnName(int): column name for given index
String[] getColumnNames()
int getCount(): number of rows
... getBlob(int), getDouble(int), getInt(int), ...
int getType(int)
boolean isFirst(), isLast()
boolean moveToFirst(), moveToLast(), moveToNext(), moveToPrevious(),
moveToPosition(int)
void registerContentObserver(ContentObserver)
...

11. CursorLoader: Querying Asynchronously in a new thread
Uri allContacts = Uri.parse("content://contacts/people");
CursorLoader cursorLoader =
new CursorLoader(this, allContacts, null, null, null, null);
Cursor c = cursorLoader.loadInBackground();
if (c.moveToFirst()) {
do {
String id = c.getString(c.getColumnIndex(
ContactsContract.Contacts._ID));
String name = c.getString(c.getColumnIndex(
ContactsContract.Contacts.DISPLAY_NAME));
...use id and name ....
} while (c.moveToNext()); }

12. Predefined Query String Constants
Uri allContacts = Uri.parse("content://contacts/people"); Uri allContacts = ContactsContract.CONTENT_URI Browser.BOOKMARKS_URI Browser.SEARCHES_URI CallLog.CONTENT_URI MediaStore.Images.Media.INTERNAL_CONTENT_URI MediaStore.Images.Media.EXTERNAL_CONTENT_URI Settings.CONTENT_URI Use withAppendedId method to retrieve a particular row, e.g., ContentUris.withAppendedId(ContactContract.Contacts.CONTENT_URI,1);

13. Inserting, Updating and Deleting
Use the insert, update, and delete methods of ContentResolver
Uri insert (Uri uri, ContentValues values)
int update (Uri uri, ContentValues values, String where, String[] selArgs)
int delete (Uri url, String where, String[] selectionArgs)
*Refer to API documents of ContentValues and ContentResolver

14. Creating User-Defined Content Providers
Extend the ContentProvider class and overwrite:
getType(): returns MIME type of the data
onCreate(): called when the provider is started
query(): query and return a Cursor object
insert(): insert a new record
delete(): delete an existing record
update(): update an existing record
Need to register the content provider in the manifest file, e.g.,
<provider
android:name="BooksProvider“
android:authority="edu.utep.cs.cs4390.provider.Books" />

15. In-Class (Pair)
Write an app to find contacts matching a given (partial) name
Display the name and phone number of matching contacts
Name: Jason_______
Found: …
Find