9.4. Create ContentProvider Create the package de.vogella.android.todos.contentprovider. Create the following MyTodoContentProvider class which extends ContentProvider. package de.vogella.android.todos.contentprovider; import java.util.Arrays; import java.util.HashSet; import android.content.ContentProvider; import android.content.ContentResolver; import android.content.ContentValues; import android.content.UriMatcher; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteQueryBuilder; import android.net.Uri; import android.text.TextUtils; import de.vogella.android.todos.database.TodoDatabaseHelper; import de.vogella.android.todos.database.TodoTable; public class MyTodoContentProvider extends ContentProvider { // database private TodoDatabaseHelper database; // Used for the UriMacher private static final int TODOS = 10; private static final int TODO_ID = 20; private static final String AUTHORITY = "de.vogella.android.todos.contentprovider"; private static final String BASE_PATH = "todos"; public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/" + BASE_PATH); public static final String CONTENT_TYPE = ContentResolver.CURSOR_DIR_BASE_TYPE + "/todos"; public static final String CONTENT_ITEM_TYPE = ContentResolver.CURSOR_ITEM_BASE_TYPE + "/todo"; private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH); static { sURIMatcher.addURI(AUTHORITY, BASE_PATH, TODOS); sURIMatcher.addURI(AUTHORITY, BASE_PATH + "/#", TODO_ID); } @Override public boolean onCreate() { database = new TodoDatabaseHelper(getContext()); return false; } @Override public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { // Uisng SQLiteQueryBuilder instead of query() method SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder(); // Check if the caller has requested a column which does not exists checkColumns(projection); // Set the table queryBuilder.setTables(TodoTable.TABLE_TODO); int uriType = sURIMatcher.match(uri); switch (uriType) { case TODOS: break; case TODO_ID: // Adding the ID to the original query queryBuilder.appendWhere(TodoTable.COLUMN_ID + "=" + uri.getLastPathSegment()); break; default: throw new IllegalArgumentException("Unknown URI: " + uri); } SQLiteDatabase db = database.getWritableDatabase(); Cursor cursor = queryBuilder.query(db, projection, selection, selectionArgs, null, null, sortOrder); // Make sure that potential listeners are getting notified cursor.setNotificationUri(getContext().getContentResolver(), uri); return cursor; } @Override public String getType(Uri uri) { return null; } @Override public Uri insert(Uri uri, ContentValues values) { int uriType = sURIMatcher.match(uri); SQLiteDatabase sqlDB = database.getWritableDatabase(); int rowsDeleted = 0; long id = 0; switch (uriType) { case TODOS: id = sqlDB.insert(TodoTable.TABLE_TODO, null, values); break; default: throw new IllegalArgumentException("Unknown URI: " + uri); } getContext().getContentResolver().notifyChange(uri, null); return Uri.parse(BASE_PATH + "/" + id); } @Override public int delete(Uri uri, String selection, String[] selectionArgs) { int uriType = sURIMatcher.match(uri); SQLiteDatabase sqlDB = database.getWritableDatabase(); int rowsDeleted = 0; switch (uriType) { case TODOS: rowsDeleted = sqlDB.delete(TodoTable.TABLE_TODO, selection, selectionArgs); break; case TODO_ID: String id = uri.getLastPathSegment(); if (TextUtils.isEmpty(selection)) { rowsDeleted = sqlDB.delete(TodoTable.TABLE_TODO, TodoTable.COLUMN_ID + "=" + id, null); } else { rowsDeleted = sqlDB.delete(TodoTable.TABLE_TODO, TodoTable.COLUMN_ID + "=" + id + " and " + selection, selectionArgs); } break; default: throw new IllegalArgumentException("Unknown URI: " + uri); } getContext().getContentResolver().notifyChange(uri, null); return rowsDeleted; } @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { int uriType = sURIMatcher.match(uri); SQLiteDatabase sqlDB = database.getWritableDatabase(); int rowsUpdated = 0; switch (uriType) { case TODOS: rowsUpdated = sqlDB.update(TodoTable.TABLE_TODO, values, selection, selectionArgs); break; case TODO_ID: String id = uri.getLastPathSegment(); if (TextUtils.isEmpty(selection)) { rowsUpdated = sqlDB.update(TodoTable.TABLE_TODO, values, TodoTable.COLUMN_ID + "=" + id, null); } else { rowsUpdated = sqlDB.update(TodoTable.TABLE_TODO, values, TodoTable.COLUMN_ID + "=" + id + " and " + selection, selectionArgs); } break; default: throw new IllegalArgumentException("Unknown URI: " + uri); } getContext().getContentResolver().notifyChange(uri, null); return rowsUpdated; } private void checkColumns(String[] projection) { String[] available = { TodoTable.COLUMN_CATEGORY, TodoTable.COLUMN_SUMMARY, TodoTable.COLUMN_DESCRIPTION, TodoTable.COLUMN_ID }; if (projection != null) { HashSet requestedColumns = new HashSet(Arrays.asList(projection)); HashSet availableColumns = new HashSet(Arrays.asList(available)); // Check if all columns which are requested are available if (!availableColumns.containsAll(requestedColumns)) { throw new IllegalArgumentException("Unknown columns in projection"); } } } } MyTodoContentProvider implements update(), insert(), delete() and query() methods. These methods map more or less directly to the SQLiteDatabase interface. It also has the checkColumns() method to validate that a query only requests valid columns. Register your ContentProvider in your AndroidManifest.xml file.
Posted on: Thu, 26 Sep 2013 06:32:33 +0000
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