Develop Reference

Passing query variables to the ContentProvider in Android

I'm wanting to know what the correct way of passing parameters for a Database query using the ContentProvider pattern is.
Is it as follow - i.e. where & args in the update method.
getContentResolver().update(uri, cv,where, args);
Or is it by appending the values at the end of the URI - As in this example in the docs - see case 2?
public class ExampleProvider extends ContentProvider {
......
......
// Implements ContentProvider.query()
public Cursor query(
Uri uri, String[] projection,String selection, String[] selectionArgs,
String sortOrder) {
switch (sUriMatcher.match(uri)) {
case 1:
if (TextUtils.isEmpty(sortOrder)) sortOrder = "_ID ASC";
break;
case 2:
selection = selection + "_ID = " uri.getLastPathSegment();
break;
And which of these approaches is the best. I've seen both used, but unsure of their respective merits.

How to implement a content provider with more than one table?

update: looking at "vnd.android.cursor.dir/vnd.google.note" and "vnd.android.cursor.item/vnd.google.note" it seemed to me as though the cursor was for one table.
From the examples it appears as though content provider were designed to work with one table. I do know how to use multiple tables in sqlite but it seems to me that the content provider seems to be about picking one row or multiple rows from one table.
see http://developer.android.com/guide/topics/providers/content-provider-creating.html
Also, see the notepad sample in adt-bundle-windows-x86-20131030\sdk\samples\android-19\legacy\NotePad\src\com\example\android\notepad
Suppose I want to have notes by topic.
I would like to have a Topics table with columns _id and Title_text.
I would like to have the Notes table with columns _id and foreign key Topic_id and Note_text.
How would one design the Topics and Notes?
But looking at the Notes sample, the content URIs and docs on content providers, it appears as though having multiple related tables is an afterthought and is not obvious to me.
from NotepadProvider.java, Notepad.java:
public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.google.note";
/**
* The MIME type of a {#link #CONTENT_URI} sub-directory of a single
* note.
*/
public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.google.note";
public static final Uri CONTENT_ID_URI_BASE
= Uri.parse(SCHEME + AUTHORITY + PATH_NOTE_ID);
/**
* The content URI match pattern for a single note, specified by its ID. Use this to match
* incoming URIs or to construct an Intent.
*/
public static final Uri CONTENT_ID_URI_PATTERN
= Uri.parse(SCHEME + AUTHORITY + PATH_NOTE_ID + "/#");
#Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
String sortOrder) {
...
switch (sUriMatcher.match(uri)) {
// If the incoming URI is for notes, chooses the Notes projection
case NOTES:
qb.setProjectionMap(sNotesProjectionMap);
break;
/* If the incoming URI is for a single note identified by its ID, chooses the
* note ID projection, and appends "_ID = <noteID>" to the where clause, so that
* it selects that single note
*/
case NOTE_ID:
qb.setProjectionMap(sNotesProjectionMap);
qb.appendWhere(
NotePad.Notes._ID + // the name of the ID column
"=" +
// the position of the note ID itself in the incoming URI
uri.getPathSegments().get(NotePad.Notes.NOTE_ID_PATH_POSITION));
break;

When creating a ContentProvider, the expectation is that other apps are going to use your database, and with that I mean other people who know nothing about your database scheme. To make things easy for them, you create and document your URIs:
To access all the books
content://org.example.bookprovider/books
to access books by id
content://org.example.bookprovider/books/#
to access books by author name
content://org.example.bookprovider/books/author
Create as many URIs as you need, that’s up to you. This way the user of your Provider can very easily access your database info, and maybe that’s why you are getting the impression that the Provider is designed to work with one table databases, but no, internally is where the work is done.
In your ContentProvider subclass, you can use a UriMatcher to identify those different URIs that are going to be passed to your ContentProvider methods (query, insert, update, delete). If the data the Uri is requesting is stored in several tables, you can actually do the JOINs and GROUP BYs or whatever you need with SQLiteQueryBuilder , e.g.
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
SQLiteQueryBuilder mQueryBuilder = new SQLiteQueryBuilder();
. . .
String Joins = " t1 INNER JOIN table2 t2 ON t2._id = t1._id"
+ " INNER JOIN table3 t3 ON t3._id = t1._id";
switch (mUriMatcher.match(uri)) {
case DATA_COLLECTION_URI:
mQueryBuilder.setTables(YourDataContract.TABLE1_NAME + Joins);
mQueryBuilder.setProjectionMap(. . .);
break;
case SINGLE_DATA_URI:
mQueryBuilder.setTables(YourDataContract.TABLE1_NAME + Joins);
mQueryBuilder.setProjectionMap(. . .);
mQueryBuilder.appendWhere(Table1._ID + "=" + uri.getPathSegments().get(1));
break;
case . . .
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
. . .
SQLiteDatabase db = mOpenHelper.getReadableDatabase();
Cursor c = mQueryBuilder.query(db, projection, selection, selectionArgs, groupBy, having, orderBy);
return c;
}
Hope it helps.

Excuse me, but I don't understand your question.
ContentProvider is designed (a one of it's aims)to wrap access to your tabels. Design of database schema is up to you.
Generally, you need to:
Define your tables/ It should be made by execution of sql command in class which extends SQLiteOpenHelper
Define an uri for them
Define a logic for queries to this tables as it was made for NOTE_ID
Update
For JOIN operations SQLiteQueryBuilder is usually used. In setTables() you need to write names of tables with JOIN clause, e.g.
.setTables(NoteColumns.TABLENAME +
" LEFT OUTER JOIN " + TopicColumns.TABLENAME + " ON " +
NoteColumns.ID + " = " + TopicColumns.ID);

Here is my code for multiple table query in content provider with projectionMap
//HashMap for Projection
mGroupImageUri = new HashMap<>();
mGroupImageUri.put(RosterConstants.JID,RosterProvider.TABLE_ROSTER+"."+RosterConstants.JID);
mGroupImageUri.put(RosterConstants.USER_NAME,RosterProvider.TABLE_ROSTER+"."+RosterConstants.USER_NAME);
mGroupImageUri.put(ChatConstants.MESSAGE,"c."+ChatConstants.MESSAGE+ " AS "+ ChatConstants.MESSAGE);
mGroupImageUri.put(ChatConstants.SENDER,"c."+ChatConstants.SENDER+" AS "+ChatConstants.SENDER);
mGroupImageUri.put(ChatConstants.URL_LOCAL,"c."+ChatConstants.URL_LOCAL+" AS "+ChatConstants.URL_LOCAL);
//case for content type of uri
case IMAGE_URI:
qBuilder.setTables(RosterProvider.TABLE_ROSTER
+ " LEFT OUTER JOIN "+ TABLE_NAME + " c"
+ " ON c."+ ChatConstants.JID + "=" + RosterProvider.TABLE_ROSTER + "."+RosterConstants.JID);
qBuilder.setProjectionMap(mGroupImageUri);
break;
//ContentResolver query for Projection form, selection and selection args
String[] PROJECTION_FROM = new String[]{
RosterConstants.JID,
RosterConstants.USER_NAME,
ChatConstants.MESSAGE,
ChatConstants.SENDER,
ChatConstants.URL_LOCAL
};
String selection = RosterProvider.TABLE_ROSTER +"."+RosterConstants.JID+ "='" + jid + "' AND " + "c."+ChatConstants.FILE_TYPE+"="+ChatConstants.IMAGE;
String[] selectionArgu = null;
String order = "c."+ChatConstants.MESSAGE+" ASC";
Cursor cursor = mContentReolver.query(ChatProvider.CONTENT_URI_GROUP_IMAGE_URI,
PROJECTION_FROM,selection, null,order);
//#ChatProvider.CONTENT_URI_GROUP_IMAGE_URI = 'your content type uri'
//#TABLE_NAME = 'table1'
//#RosterProvider.TABLE_ROSTER ='table2'

Using SearchManager's SUGGEST_COLUMN_ICON_1 to display a local file

I'm implementing my own SearchRecentSuggestionsProvider and everything's working except one thing: I can't get the device search to display icons for the results. I'd like to display images from my application's data folder (located at /{sdcard}/Android/data/package_name/files/)
According to the documentation, it's achievable by using SearchManager.SUGGEST_COLUMN_ICON_1, and it apparently supports a number of schemes, including ContentResolver.SCHEME_FILE, which is file. Here's a quote from the official docs:
Column name for suggestions cursor. Optional. If your cursor includes this column, then all suggestions will be provided in a format that includes space for two small icons, one at the left and one at the right of each suggestion. The data in the column must be a resource ID of a drawable, or a URI in one of the following formats:
content (SCHEME_CONTENT)
android.resource (SCHEME_ANDROID_RESOURCE)
file (SCHEME_FILE)
I've tried a number of obvious things, including manual creation of the file URI and automated creation using Uri.Builder(). None of this worked.
I also found someone else asking about the same thing on Google Groups, and it's sadly unanswered: https://groups.google.com/forum/#!topic/android-developers/MJj7GIaONjc
Does anyone have any experience in getting the device search to display local images from the device?
UPDATE (December 15):
I've just tried using the ContentProvider with a SearchView as the searchable info, and it works exactly as expected - including the cover art images. Still, global search doesn't show it...

I had a similar issue and could not make the other solutions work. I finally substituted the cursor with a new one containing the data I needed in query().
public class RecentQueriesProvider extends SearchRecentSuggestionsProvider {
public final static String AUTHORITY = "com.package.RecentQueriesProvider";
public final static int MODE = DATABASE_MODE_QUERIES;
public RecentQueriesProvider() {
setupSuggestions(AUTHORITY, MODE);
}
// We override query() to replace the history icon in the recent searches suggestions. We create a new cursor
#Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
Cursor superCursor = super.query(uri, projection, selection, selectionArgs, sortOrder);
Uri iconUri = Uri.parse("android.resource://" + getContext().getPackageName() + "/drawable/ic_action_time");
MatrixCursor newCursor = new MatrixCursor(superCursor.getColumnNames());
superCursor.moveToFirst();
while (superCursor.moveToNext()){
newCursor.addRow(new Object[]{
superCursor.getInt(superCursor.getColumnIndex(SearchManager.SUGGEST_COLUMN_FORMAT)),
iconUri,
superCursor.getString(superCursor.getColumnIndex(SearchManager.SUGGEST_COLUMN_TEXT_1)),
superCursor.getString(superCursor.getColumnIndex("suggest_intent_query")),
superCursor.getInt(superCursor.getColumnIndex("_id"))
});
}
return newCursor;
}
}

One way is to copy source code from android.content.SearchRecentSuggestionsProvider, place it in your class that extends ContentProvider, and customize setupSuggestions(String, int). Specifically, you would be changing this:
Uri uriFile = Uri.fromFile(new File("path/to/file"));
mSuggestionProjection = new String [] {
"0 AS " + SearchManager.SUGGEST_COLUMN_FORMAT,
// Here, you would return a file uri: 'uriFile'
"'android.resource://system/"
+ com.android.internal.R.drawable.ic_menu_recent_history + "' AS "
+ SearchManager.SUGGEST_COLUMN_ICON_1,
"display1 AS " + SearchManager.SUGGEST_COLUMN_TEXT_1,
"query AS " + SearchManager.SUGGEST_COLUMN_QUERY,
"_id"
};
I prefer the following though. Extend SearchRecentSuggestionsProvider and override the query(...) method. Here, intercept SearchManager.SUGGEST_URI_PATH_QUERY and return a cursor.
public class SearchSuggestionProvider extends SearchRecentSuggestionsProvider {
private UriMatcher matcher;
private static final int URI_MATCH_SUGGEST = 1;
public SearchSuggestionProvider() {
super();
matcher = new UriMatcher(UriMatcher.NO_MATCH);
// Add uri to return URI_MATCH_SUGGEST
matcher.addURI(SearchSuggestionProvider.class.getName(),
SearchManager.SUGGEST_URI_PATH_QUERY, URI_MATCH_SUGGEST);
setupSuggestions(SearchSuggestionProvider.class.getName(),
DATABASE_MODE_QUERIES);
}
#Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// special case for actual suggestions (from search manager)
if (matcher.match(uri) == URI_MATCH_SUGGEST) {
// File to use
File f = new File("/path/to/file");
Uri uriFile = Uri.fromFile(f);
final String[] PROJECTION = new String[] {
"_id",
"display1 AS " + SearchManager.SUGGEST_COLUMN_TEXT_1,
"query AS " + SearchManager.SUGGEST_COLUMN_QUERY,
"'" + uriFile + "'" + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1,
};
final Uri URI = Uri.parse("content://" +
SearchSuggestionProvider.class.getName() + "/suggestions");
// return cursor
return getContext().getContentResolver().query(
URI,
PROJECTION,
"display1 LIKE ?",
new String[] {selectionArgs[0] + "%"},
"date DESC");
}
// Let super method handle the query if the check fails
return super.query(uri, projection, selection, selectionArgs, sortOrder);
}
}

notifyChange with changed uri from contentProvider.update()

i have implemented update() of ContentProvider and notifying to observer using getContext().getContentResolver().notifyChange(uri, null);
my obvious need is that whenever just one row is effected i want to notify with row specific uri, but could not find way to do so.
an additional query like "select id where selectionArgs" can do this but this will be a foolish way.
onchange(boolean, uri) get complete uri instead of specific row, easy to understand that this is because ContentProvider.update() is sending the same.
some code for more clarity
update() method of MyContentProvider
#Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
Log.d("TAG", "update " + uri.getPath());
int count = 0;
switch (uriMatcher.match(uri)) {
case BOOKS:
count = booksDB.update(DATABASE_TABLE, values, selection, selectionArgs);
break;
case BOOK_ID:
count = booksDB.update(DATABASE_TABLE, values,
_ID + " = " + uri.getPathSegments().get(1)
+ (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""),
selectionArgs);
break;
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
if (count == 1) {
Cursor c = query(uri, new String[] { _ID }, selection, selectionArgs, null);
long rowId = Long.valueOf(c.getString(c.getColumnIndex(_ID)));
uri = ContentUris.withAppendedId(CONTENT_URI, rowId);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
i will update table some how like
getContentResolver().update(MyContentProvider.CONTENT_URI, values1, MyContentProvider._ID+"<?", new String[]{"3"}));
frankly saying, code has barely related to question, just trying to give you some context

In your provider method, just return the uri with the id appended
#Override
public Uri insert(Uri uri, ContentValues values) {
Log.i(TAG, "insert " + uri);
final SQLiteDatabase db = mOpenHelper.getWritableDatabase();
final int match = URI_MATCHER.match(uri);
Uri returnUri;
switch (match) {
case MESSAGE: {
long _id = db.insert(MessageContract.MessageEntry.TABLE_NAME, null, values);
if (_id > 0)
returnUri = ContentUris.withAppendedId(MessageContract.MessageEntry.CONTENT_URI, _id);
else
throw new android.database.SQLException("Failed to insert row into " + uri);
break;
}
default:
throw new UnsupportedOperationException("Unknown uri: " + uri);
}
getContext().getContentResolver().notifyChange(returnUri, null);
return returnUri;
}
And register your observer with true for descendents.
getContentResolver().registerContentObserver(MessageContract.MessageEntry.CONTENT_URI, true, mContentObserver);
To get the id from a Uri you can use ContentUris.parseId(uri)

Unfortunately I'm not able to suggest easy solution (because I'm not aware of full code and updates You need to run), there's some ways we You could try (some of them I've implemented in mine applications):
Provide ids in ContentValues - this way looks not applicable for Your case and it needs loop with calls to notifyChange();
Provide specific Uri for requests with queries (only some specific apps needs many various queries in selection, usually it's much easier to include query parameter in Uri). After another part of the program get notification with that specific Uri it will be able to check if it's 'current item' was updated and act appropriately (e.g. simplest case with list of articles and one article open in separate activity; then You update list of articles in the background from server You might need to update currently open article also and so, need to know if it was updated). You should be able to check particular item on the side of the observer using just received Uri, because it (Uri) will contain parameter(s) You've used for query;

You can pass the ID via ContentValues, and append it to the notification url. This way you don't have to make a separate query.
#Override
public int update(#NonNull Uri uri, ContentValues values, String selection, String[] selectionArgs) {
int rows = _database.update(getTableName(), values, selection, selectionArgs);
if (rows > 0) {
Uri itemUri = ContentUris.withAppendedId(uri, values.getAsLong(DatabaseModel.COLUMN_ID)); // DatabaseModel.COLUMN_ID is "_id"
getContext().getContentResolver().notifyChange(itemUri, null);
}
return rows;
}

Android ContentProvider URI scheme to notify CursorAdapters listening on OUTER JOIN queries

I have an Android ContentProvider which allows to do LEFT OUTER JOIN queries on a SQLite database.
Let's assume in the database I have 3 tables, Users, Articles and Comments. The ContentProvider is something like the following:
public class SampleContentProvider extends ContentProvider {
private static final UriMatcher sUriMatcher;
public static final String AUTHORITY = "com.sample.contentprovider";
private static final int USERS_TABLE = 1;
private static final int USERS_TABLE_ID = 2;
private static final int ARTICLES_TABLE = 3;
private static final int ARTICLES_TABLE_ID = 4;
private static final int COMMENTS_TABLE = 5;
private static final int COMMENTS_TABLE_ID = 6;
private static final int ARTICLES_USERS_JOIN_TABLE = 7;
private static final int COMMENTS_USERS_JOIN_TABLE = 8;
// [...] other ContentProvider methods
#Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
String table = getTableName(uri);
// SQLiteWrapper is a wrapper class to manage a SQLiteHelper
Cursor c = SQLiteWrapper.get(getContext()).getHelper().getReadableDatabase()
.query(table, projection, selection, selectionArgs, null, null, sortOrder);
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;
}
#Override
public Uri insert(Uri uri, ContentValues values) {
String table = getTableName(uri);
// SQLiteWrapper is a wrapper class to manage a SQLiteHelper
long id = SQLiteWrapper.get(getContext()).getHelper().getWritableDatabase()
.insert(table, null, values);
Uri itemUri = ContentUris.withAppendedId(uri, id);
getContext().getContentResolver().notifyChange(itemUri, null);
return itemUri;
}
private String getTableName(Uri uri) {
switch (sUriMatcher.match(uri)) {
case USERS_TABLE:
case USERS_TABLE_ID:
return "Users";
case ARTICLES_TABLE:
case ARTICLES_TABLE_ID:
return "Articles";
case COMMENTS_TABLE:
case COMMENTS_TABLE_ID:
return "Comments";
case ARTICLES_USERS_JOIN_TABLE:
return "Articles a LEFT OUTER JOIN Users u ON (u._id = a.user_id)";
case COMMENTS_USERS_JOIN_TABLE:
return "Comments c LEFT OUTER JOIN Users u ON (u._id = c.user_id)";
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
}
static {
sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
sUriMatcher.addURI(AUTHORITY, "users", USERS_TABLE);
sUriMatcher.addURI(AUTHORITY, "articles", ARTICLES_TABLE);
sUriMatcher.addURI(AUTHORITY, "comments", COMMENTS_TABLE);
sUriMatcher.addURI(AUTHORITY, "users" + "/#", USERS_TABLE_ID);
sUriMatcher.addURI(AUTHORITY, "articles" + "/#", ARTICLES_TABLE_ID);
sUriMatcher.addURI(AUTHORITY, "comments" + "/#", COMMENTS_TABLE_ID);
sUriMatcher.addURI(AUTHORITY, "???", ARTICLES_USERS_JOIN_TABLE); // what uri here?
sUriMatcher.addURI(AUTHORITY, "???", COMMENTS_USERS_JOIN_TABLE); // what uri here?
}
}
What's the best URI scheme to notify all CursorAdapters listening on joined and non-joined queries every time I insert (or update) a row in the Users table?
In other words, if I add or update a new row in one of the tables, I want to send a single notification with getContext().getContentResolver().notifyChange(itemUri, null) so that all the CursorAdapters listening on any query (USERS_TABLE, ARTICLES_USERS_JOIN_TABLE, COMMENTS_USERS_JOIN_TABLE) receive a notification to update their content.
If this is not possible, is there an alternative way to notify all the observers?

You can have special Uri's to query with:
sUriMatcher.addURI(AUTHORITY, "articlesusers", ARTICLES_USERS_JOIN_TABLE);
sUriMatcher.addURI(AUTHORITY, "commentsusers", COMMENTS_USERS_JOIN_TABLE);
But I can't think of a way to send a single notification. It seems your best choice is to send a notification for each Uri that refers to the table being modified. So your insert/update/delete methods would call notifyChange multiple times depending on the table affected. For changes to "users" it would be 3 notifications--users, articlesusers and commentsusers--since they all depend on the "users" table.

As answered by prodaea, here is another alternative you can use for notification Uri. This is not a perfect solution, but it uses only one Uri for notification.
The solution is to use the main Uri without any table name (e.g:content://com.example.app.provider/) as the notification Uri in the query method for ARTICLES_USERS_JOIN_TABLE and COMMENTS_USERS_JOIN_TABLE. So, the related cursor will be notified whenever there is change in any table. There is one limitation though. That is, ARTICLES_USERS_JOIN_TABLE cursor will be notified even when there is change in Articles table.
For tables, Users' andArticles', you can use their specific Uris for notification.