A Content Provider manages access to a centralized database and allows other applications to query or modify this data through a common interface. It implements methods like query(), insert(), update(), and delete() to retrieve, modify and delete data in response to requests from other applications via a ContentResolver. The Content Provider must define an authority and URI paths to identify its data tables. It uses a SQLite database to manage the underlying data and a UriMatcher to route incoming requests to the correct methods.

1. Content Providers

2. Content Providers
A Content Provider is a main component that manages access to
a centralized repository of data.
The main purpose is to share data with other applications (then
communicates data in interprocess communication). It is used to
create a database for internal research application.
A Content Provider manages a SQLite DB.
There are default Content Providers in the system to access
common data:
● Dictionary
● Contacts
● SMS
● Calls
● ...
Content Provider

3. Content Providers
A Content Provider is accessed through a client object called
ContentResolver that enables interprocess Communication.
For access to any Content Provider the application must specify
its permissions in the Manifest file. Typically permissions are
divided into
● Reading permissions
● Writing permissions
When you ask permission in writing is not necessary to require
reading ones.
Ex. To request permission to read the user dictionary, you must
add permission request in the Manifest file and you can not
request access at runtime:
<uses-permission android:name="android.permission.READ_USER_DICTIONARY">
Access

4. Content Providers
To perform a query on a ContentProvider you can use
ContentResolver.query() method to get the Cursor to read:
// Queries the user dictionary and returns results
mCursor = getContentResolver().query(
mUri, // The content URI of the words table
mProjection, // The columns to return for each row
mSelectionClause // Selection criteria
mSelectionArgs, // Selection criteria
mSortOrder); // The sort order for the returned rows
Parameters:
● Uri: Table name
● Projection: String array to specify what columns to invlude in
the query result
● Selection: string that specifies selection criteria
● SelectionArgs: argument strings for selection
● SortOrder: order of the query result
Query

5. Content Providers
The table identifying Uri is composed by:
● Prefix: "content://“
● Authority: it identifies the Provider
● Path: it identifies the table using its name
Es. content://user_dictionary/words
To create the Uri, use utility class called Uri, Uri.Builder and
ContentUris that simplify the management of Uri and provide
access to a single row of the table with the static method
ContentUris.withAppendedId()
Uri singleUri = ContentUris.withAppendedId(UserDictionary.Words.CONTENT_URI,4);
Query - Uri

6. Content Providers
To construct a SQL query you must follow its syntax
String[] mSelectionArgs = {""};
mSearchString = mSearchWord.getText().toString();
if (TextUtils.isEmpty(mSearchString)) {
mSelectionClause = null;
mSelectionArgs[0] = "";
} else {
mSelectionClause = UserDictionary.Words.WORD + " = ?";
mSelectionArgs[0] = mSearchString;
}
mCursor = getContentResolver().query(
UserDictionary.Words.CONTENT_URI,
mProjection,
mSelectionClause
mSelectionArgs,
MsortOrder);
SELECT _ID, word, locale FROM words WHERE word = <userinput> ORDER BY word ASC;
Query - Statement

7. Content Providers
The "?" in selectionClause and selectionArgs are useful to protect
the DB from unknowing operations like dropthe user would insert.
Ex.
String mSelectionClause = "var = " + mUserInput;
The user would insert "nothing: DROP TABLE *;". Instead the
following is used to avoid problema:
String mSelectionClause = "var = ?";
String[] selectionArgs = {""};
selectionArgs[0] = mUserInput;
Query - Statement

8. Content Providers
The ContentResolver.query() method returns a Cursor that
contains all the rows resulting from the query with the specified
columns from the projection. For this reason, you must iterate
over the lines and you can retrieve the value for each column.
if(mCursor!=null){
while(mCursor.moveToNext()){
mCursor.getBlob(mCursor.getColumnIndex(BLOB_COLUMN_NAME));
mCursor.getDouble(mCursor.getColumnIndex(DOUBLE_COLUMN_NAME));
mCursor.getFloat(mCursor.getColumnIndex(FLOAT_COLUMN_NAME));
mCursor.getInt(mCursor.getColumnIndex(INT_COLUMN_NAME));
mCursor.getLong(mCursor.getColumnIndex(LONG_COLUMN_NAME));
mCursor.getShort(mCursor.getColumnIndex(SHORT_COLUMN_NAME));
mCursor.getString(mCursor.getColumnIndex(STRING_COLUMN_NAME));
}
}else{
//...
}
Query - Cursor

9. Content Providers
ContentResolver.insert() method inserts a new rowin the provider
table and returns the created Uri.
content://user_dictionary/words/<id_value>
The insertion takes place via a contentValues object that contains
the values of the new row. You do not need to manage _ID
because it is handled automatically. To insert a null value use
ContentValues.putNull().
Uri mNewUri;
ContentValues mNewValues = new ContentValues();
mNewValues.put(UserDictionary.Words.APP_ID, "example.user");
mNewValues.put(UserDictionary.Words.LOCALE, "en_US");
mNewValues.put(UserDictionary.Words.WORD, "insert");
mNewValues.put(UserDictionary.Words.FREQUENCY, "100");
mNewUri = getContentResolver().insert(
UserDictionary.Word.CONTENT_URI,// the user dictionary content URI
mNewValues // the values to insert
);
String mSelectionClause = "var = ?";
String[] selectionArgs = {""};
selectionArgs[0] = mUserInput;
Insert

10. Content Providers
The method ContentResolver.update() updates the rows resulting
from the query with the values specified by contentValues.
ContentValues mUpdateValues = new ContentValues();
String mSelectionClause = UserDictionary.Words.LOCALE + "LIKE ?";
String[] mSelectionArgs = {"en_%"};
int mRowsUpdated = 0;
mUpdateValues.putNull(UserDictionary.Words.LOCALE);
mRowsUpdated = getContentResolver().update(
UserDictionary.Words.CONTENT_URI,// the user dictionary content URI
mUpdateValues // the columns to update
mSelectionClause // the column to select on
mSelectionArgs // the value to compare to
);
Update

11. Content Providers
The method ContentResolver.delete() delete query resulting
rows.
String mSelectionClause = UserDictionary.Words.APP_ID + " LIKE ?";
String[] mSelectionArgs = {"user"};
int mRowsDeleted = 0;
mRowsDeleted = getContentResolver().delete(
UserDictionary.Words.CONTENT_URI,// the user dictionary content URI
mSelectionClause // the column to select on
mSelectionArgs // the value to compare to
);
Delete

12. Content Providers
A ContentProvider is necessary only if:
● You need to share data with other applications
● You want to develop a custom search system for
autocomplete text
In all other cases a Database SQLite is sufficient to achieve the
purpose.
Creation - Analysis

13. Content Providers
To configure a Content Provider you must establish its Authority
and the Path of its tables.
● Authority: to avoid conflicts extend the application package to
make it unique
<provider
android:name=".ExampleProvider"
android:authorities="com.example.<appname>.provider" >
</provider>
● Path: to define tables path extend Authority:
com.example.<appname>.provider/table1
com.example.<appname>.provider/table2
...
Creation - Design

14. Content Providers
When a ContentProvider receives a Uri it must understand what
action to take. Use a UriMatcher that maps Uri to integers.
public class ExampleProvider extends ContentProvider {
private static final UriMatcher sUriMatcher;
static {
sUriMatcher.addURI("com.example.app.provider", "table3", 1);
sUriMatcher.addURI("com.example.app.provider", "table3/#", 2);
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String
sortOrder) {
switch (sUriMatcher.match(uri)) {
// If the incoming URI was for all of table3
case 1:
if (TextUtils.isEmpty(sortOrder)) sortOrder = "_ID ASC";
break;
// If the incoming URI was for a single row
case 2:
selection = selection + "_ID = " + uri.getLastPathSegment();
break;
default:
// If the URI is not recognized, you should do some error handling here.
}
// call the code to actually do the query
}
}
Creation - Design

15. Content Providers
The abstract class ContentProvider must manage accesses to
data by calls from a ContentResolver from other processes
and/or applications. The methods to implement are:
● ContentProvider.query()
● ContentProvider.insert()
● ContentProvider.update()
● ContentProvider.delete()
● ContentProvider.getType()
● ContentProvider.onCreate()
These methods have the same signature as the ContentResolver
ones to simplify their use.
Creation - Implementation

16. Content Providers
Using a SQLite Database simply return the Cursor returned by
SQLiteDatabase.query()
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
queryBuilder.setTables(TABLE);
int uriType = sURIMatcher.match(uri);
switch (uriType) {
case 1:
queryBuilder.appendWhere(Contract._ID + "="
+ uri.getLastPathSegment());
break;
case 2:
break;
default:
throw new IllegalArgumentException("Unknown URI");
}
Cursor cursor = queryBuilder.query(database, projection, selection,
selectionArgs, groupBy, having, sortOrder);
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return cursor;
}
Creation – Implementation -
query()

17. Content Providers
@Override
public Uri insert(Uri uri, ContentValues values) {
int uriType = sURIMatcher.match(uri);
long id;
switch (uriType) {
case 1:
id = database.insert(TABLE_NAME, null, values);
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return ContentUris.withAppendedId(Contract.CONTENT_URI, id);
}
Creation – Implementation -
insert()

18. Content Providers
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
int rowsDeleted = database.delete(TABLE_NAME, selection,
selectionArgs);
getContext().getContentResolver().notifyChange(uri, null);
return rowsDeleted;
}
Creation – Implementation -
delete()

19. Content Providers
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
int rowsUpdated = 0;
int uriType = sURIMatcher.match(uri);
switch (uriType) {
case 1:
rowsUpdated = database.update(TABLE_NAME, values, selection,
selectionArgs);
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return rowsUpdated;
}
Creation – Implementation -
update()

20. Content Providers
@Override
public boolean onCreate() {
dbHelper = new DatabaseHelper(getContext());
database = dbHelper.getWritableDatabase();
return database != null;
}
protected static final class DatabaseHelper extends SQLiteOpenHelper {
private static final String DBNAME = "db_name";
private static final String SQL_CREATE = "CREATE TABLE "
+ "main ( _ID INTEGER PRIMARY KEY, WORD TEXT, FREQUENCY INTEGER, LOCALE TEXT )";
public WeatherDatabaseHelper(Context context) {
super(context, DBNAME, null, 1);
}
public void onCreate(SQLiteDatabase db) {
db.execSQL(SQL_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
}
Creation – Implementation -
onCreate()

21. Content Providers
The method returns a string in MIME format that describes the
type of data returned by the Uri argument. In the case of the
SQLite Database, string is composed in this way:
● Type: vnd
● Subtype:
● Single row: android.cursor.item/
● Multiple rows: android.cursor.dir/
● Provider: vnd.<name>.<type>
@Override
public String getType(Uri uri) {
switch (sURIMatcher.match(uri)){
case 1:
return "vnd.android.cursor.dir/vnd.com.example.provider";
case 2:
return "vnd.android.cursor.item/vnd.com.example.provider";
default:
throw new IllegalArgumentException("Unsupported URI: " + uri);
}
}
Creation – Implementation -
getType()

22. Content Providers
To allow other applications access to the Content Provider you
must specify required permissions in the Manifest file.
<provider
android:name=".ExampleProvider"
android:authorities="com.example.android.provider"
android:permission="com.example.android.provider.PERMISSION"
android:readPermission="com.example.android.provider.READ_PERMISSION"
android:writePermission="com.example.android.provider.WRITE_PERMISSION" >
</provider>
Creation - Permission