am 343f581d: Merge "fix typo and clarify class references in database lesson... (f0380a26) · Commits · e / os / android_frameworks_base

docs/html/training/basics/data-storage/databases.jd

+32 −34

Original line number	Diff line number	Diff line
		@@ -73,6 +73,12 @@ single table:</p>


		<pre>
		public final class FeedReaderContract {
		// To prevent someone from accidentally instantiating the contract class,
		// give it an empty constructor.
		public FeedReaderContract() {}

		/* Inner class that defines the table contents */
		public static abstract class FeedEntry implements BaseColumns {
		public static final String TABLE_NAME = "entry";
		public static final String COLUMN_NAME_ENTRY_ID = "entryid";
		@@ -80,15 +86,7 @@ public static abstract class FeedEntry implements BaseColumns {
		public static final String COLUMN_NAME_SUBTITLE = "subtitle";
		...
		}
		</pre>


		<p>To prevent someone from accidentally instantiating the contract class, give
		it an empty constructor. </p>

		<pre>
		// Prevents the FeedReaderContract class from being instantiated.
		private FeedReaderContract() {}
		}
		</pre>


		@@ -103,15 +101,15 @@ statements that create and delete a table:</P>
		private static final String TEXT_TYPE = " TEXT";
		private static final String COMMA_SEP = ",";
		private static final String SQL_CREATE_ENTRIES =
		"CREATE TABLE " + FeedReaderContract.FeedEntry.TABLE_NAME + " (" +
		FeedReaderContract.FeedEntry._ID + " INTEGER PRIMARY KEY," +
		FeedReaderContract.FeedEntry.COLUMN_NAME_ENTRY_ID + TEXT_TYPE + COMMA_SEP +
		FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE + TEXT_TYPE + COMMA_SEP +
		"CREATE TABLE " + FeedEntry.TABLE_NAME + " (" +
		FeedEntry._ID + " INTEGER PRIMARY KEY," +
		FeedEntry.COLUMN_NAME_ENTRY_ID + TEXT_TYPE + COMMA_SEP +
		FeedEntry.COLUMN_NAME_TITLE + TEXT_TYPE + COMMA_SEP +
		... // Any other options for the CREATE command
		" )";

		private static final String SQL_DELETE_ENTRIES =
		"DROP TABLE IF EXISTS " + TABLE_NAME_ENTRIES;
		"DROP TABLE IF EXISTS " + FeedEntry.TABLE_NAME;
		</pre>

		<p>Just like files that you save on the device's <a
		@@ -191,15 +189,15 @@ SQLiteDatabase db = mDbHelper.getWritableDatabase();

		// Create a new map of values, where column names are the keys
		ContentValues values = new ContentValues();
		values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_ENTRY_ID, id);
		values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE, title);
		values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_CONTENT, content);
		values.put(FeedEntry.COLUMN_NAME_ENTRY_ID, id);
		values.put(FeedEntry.COLUMN_NAME_TITLE, title);
		values.put(FeedEntry.COLUMN_NAME_CONTENT, content);

		// Insert the new row, returning the primary key value of the new row
		long newRowId;
		newRowId = db.insert(
		FeedReaderContract.FeedEntry.TABLE_NAME,
		FeedReaderContract.FeedEntry.COLUMN_NAME_NULLABLE,
		FeedEntry.TABLE_NAME,
		FeedEntry.COLUMN_NAME_NULLABLE,
		values);
		</pre>

		@@ -227,18 +225,18 @@ SQLiteDatabase db = mDbHelper.getReadableDatabase();
		// Define a <em>projection</em> that specifies which columns from the database
		// you will actually use after this query.
		String[] projection = {
		FeedReaderContract.FeedEntry._ID,
		FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE,
		FeedReaderContract.FeedEntry.COLUMN_NAME_UPDATED,
		FeedEntry._ID,
		FeedEntry.COLUMN_NAME_TITLE,
		FeedEntry.COLUMN_NAME_UPDATED,
		...
		};

		// How you want the results sorted in the resulting Cursor
		String sortOrder =
		FeedReaderContract.FeedEntry.COLUMN_NAME_UPDATED + " DESC";
		FeedEntry.COLUMN_NAME_UPDATED + " DESC";

		Cursor c = db.query(
		FeedReaderContract.FeedEntry.TABLE_NAME, // The table to query
		FeedEntry.TABLE_NAME, // The table to query
		projection, // The columns to return
		selection, // The columns for the WHERE clause
		selectionArgs, // The values for the WHERE clause
		@@ -262,7 +260,7 @@ For example:</p>
		<pre>
		cursor.moveToFirst();
		long itemId = cursor.getLong(
		cursor.getColumnIndexOrThrow(FeedReaderContract.FeedEntry._ID)
		cursor.getColumnIndexOrThrow(FeedEntry._ID)
		);
		</pre>

		@@ -282,7 +280,7 @@ immune to SQL injection.</p>

		<pre>
		// Define 'where' part of query.
		String selection = FeedReaderContract.FeedEntry.COLUMN_NAME_ENTRY_ID + " LIKE ?";
		String selection = FeedEntry.COLUMN_NAME_ENTRY_ID + " LIKE ?";
		// Specify arguments in placeholder order.
		String[] selectionArgs = { String.valueOf(rowId) };
		// Issue SQL statement.
		@@ -305,10 +303,10 @@ SQLiteDatabase db = mDbHelper.getReadableDatabase();

		// New value for one column
		ContentValues values = new ContentValues();
		values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE, title);
		values.put(FeedEntry.COLUMN_NAME_TITLE, title);

		// Which row to update, based on the ID
		String selection = FeedReaderContract.FeedEntry.COLUMN_NAME_ENTRY_ID + " LIKE ?";
		String selection = FeedEntry.COLUMN_NAME_ENTRY_ID + " LIKE ?";
		String[] selectionArgs = { String.valueOf(rowId) };

		int count = db.update(