Cursor in Android

Cursors

Cursors are the ones that contain the result set of a query made against a database in Android.

The Cursor class has an API that allows an app to read (in a type-safe manner) the columns that were returned from the query as well as iterate over the rows of the result set.

Once a cursor has been returned from a database query, App needs to iterate over the result set and read the column data from the cursor

In order to get the columns and rows, we use the statement:

Int col = cursor.getColumnCount();

Int row =  cursor.getCount();

In order to get the column names, we use:

String[] columnNames = cursor.getColumnNames();

Cursor cursor = database.query(TABLE_NAME, columnNames, null, null, null, null, null);

The Cursor class provides the following methods to manipulate its internal position:

·         boolean Cursor.move(int offset): Moves the position by the given offset

·         boolean Cursor.moveToFirst(): Moves the position to the first row

·         boolean Cursor.moveToLast(): Moves the position to the last row

·         boolean Cursor.moveToNext(): Moves the cursor to the next row relative to the current position

·         boolean Cursor.moveToPosition(int position): Moves the cursor to the specified position

·         Cursor.moveToPrevious(): Moves the cursor to the previous row relative to the current position

SQLiteDatabase db = getDatabase();

String[] columns = {"first_name", "last_name", "id"};

Cursor cursor = db.query("people", columns, null, null, null, null, null);

while(cursor.moveToNext()) {
    int index;

    index = cursor.getColumnIndexOrThrow("first_name");
    String firstName = cursor.getString(index);

    index = cursor.getColumnIndexOrThrow("last_name");
    String lastName = cursor.getString(index);

    index = cursor.getColumnIndexOrThrow("id");
    long id = cursor.getLong(index);

    //... do something with data
}