Android Tutorial

By : Ketan Bhimani

350 

Implementing Important Content Provider Methods

This section shows example implementations of each of the

methods that are used by the system to call this content provider

when another application wants to use it. The system, in this case,

is the ContentResolver interface that was used indirectly in the

previous section when built-in content providers were used.

Some of these methods can make use of a helper class provided by

the Android SDK, UriMatcher, which is used to match incoming Uri

values to patterns that help speed up development.The use of

UriMatcher is described and then used in the implementation of

these methods.

Implementing the query() Method

Let’s start with a sample query implementation. Any query

implementation needs to return a Cursor object. One convenient

way to get a Cursor object is to return the Cursor from the

underlying SQLite database that many content providers use. In

fact, the interface to ContentProvider.query() is compatible with the

SQL ite Query Builder .query() call. This example uses it to quickly

build the query and return a Cursor object.

public Cursor query(Uri uri, String[] projection,
String selection, String[] selectionArgs,
String sortOrder) {
SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();
qBuilder.setTables(TrackPointDatabase.TRACKPOINTS_TABLE);
if ((sURIMatcher.match(uri)) == TRACKPOINT_ID) {
qBuilder.appendWhere(“_id=” + uri.getLastPathSegment());
}
Cursor resultCursor = qBuilder.query(mDB.getReadableDatabase(),
projection, selection, selectionArgs, null, null, sortOrder, null);
resultCursor.setNotificationUri(getContext().getContentResolver(),
uri);
return resultCursor;
}