Key-Value Table

KeyValueTable

/**
 * 专门用来存储key-value的表格，shared preferences的db版
 * From db version 1
 * @author viyu
 */
public final class KeyValueTable {
         
	/**
	 * @param key
	 */
	public static void deleteByKey(String key) {
		SQLiteDatabase db = SQLHelper.getInstance().getWritableDatabase();
		db.delete(KeyValueEntry.TABLE_NAME, KeyValueEntry.COLUMN_NAME_KEY + "='" + key + "'", null);
		db.close();
	}

	public static void insertKeyValuePair(KeyValueEntry entry) {
		SQLiteDatabase db = SQLHelper.getInstance().getWritableDatabase();
		ContentValues values = new ContentValues();
		//
		values.put(KeyValueEntry.COLUMN_NAME_KEY, entry.getKey());
		values.put(KeyValueEntry.COLUMN_NAME_VALUE, entry.getValue());
		//
		db.insert(KeyValueEntry.TABLE_NAME, null, values);
		db.close();
	}

	public static String getValueByKey(String key) {
		SQLiteDatabase db = SQLHelper.getInstance().getReadableDatabase();
		String[] projection = { KeyValueEntry.COLUMN_NAME_VALUE };
		String selection = KeyValueEntry.COLUMN_NAME_KEY + "='" + key + "'";
		Cursor cursor = db.query(KeyValueEntry.TABLE_NAME, projection, selection, null, null, null, null);
		if (cursor == null || cursor.moveToFirst() == false) {
			cursor.close();
			db.close();
			return null;
		}
		//
		String value = null;
		if(cursor.moveToFirst()) {
			int valueColumn = cursor.getColumnIndex(KeyValueTable.KeyValueEntry.COLUMN_NAME_VALUE);
			value = cursor.getString(valueColumn);
		}
		cursor.close();
		db.close();
		return value;
	}

	public static class KeyValueEntry implements BaseColumns {
		/**
		 * 表名
		 */
		public static final String TABLE_NAME = "DB_KeyValue";

		/**
		 * key
		 */
		public static final String COLUMN_NAME_KEY = "key";
		/**
		 * value
		 */
		public static final String COLUMN_NAME_VALUE = "value";

		private String mKey = null;
		private String mValue = null;

		public KeyValueEntry(String key, String value) {
			mKey = key;
			mValue = value;
		}

		public String getKey() {
			return mKey;
		}

		public String getValue() {
			return mValue;
		}
	}

	public static final String SQL_CREATE_TABLE = "CREATE TABLE " + KeyValueEntry.TABLE_NAME + " ("
			+ KeyValueEntry.COLUMN_NAME_KEY + " TEXT PRIMARY KEY" + SEP_COMMA + KeyValueEntry.COLUMN_NAME_VALUE + TYPE_TEXT
			+ " )";

	public static final String SQL_DROP_TABLE = "DROP TABLE IF EXISTS " + KeyValueEntry.TABLE_NAME;
	
	public static final String TYPE_TEXT = " TEXT";
	
	public static final String TYPE_INTEGER = " INTEGER";

	public static final String SEP_COMMA = ",";
}