Reading retrieved data

The Cursor object returned by a query provides access to a recordset of results. If you have queried for a specific record by ID, this set will contain only one value. Otherwise, it can contain multiple values. (If there are no matches, it can also be empty.) You can read data from specific fields in the record, but you must know the data type of the field, because the Cursor object has a separate method for reading each type of data — such as getstring(), getint(), and getFloat(). (However, for most types, if you call the method for reading strings, the Cursor object will give you the String representation of the data.) The Cursor lets you request the column name from the index of the column, or the index number from the column name.

The following snippet demonstrates reading names and phone numbers from the query illustrated earlier:

import android.provider.Contacts.People;

private void getColumnData(Cursor cur){ if (cur.moveToFirst()) {

String name; String phoneNumber;

int nameColumn = cur.getColumnlndex(People.NAME); int phoneColumn = cur.getColumnlndex(People.NUMBER); String imagePath;

// Get the field values name = cur.getString(nameColumn);

phoneNumber = cur.getString(phoneColumn);

// Do something with the values. } while (cur.moveToNext());

If a query can return binary data, such as an image or sound, the data may be directly entered in the table or the table entry for that data may be a string specifying a content: URI that you can use to get the data. In general, smaller amounts of data (say, from 20 to 50K or less) are most often directly entered in the table and can be read by calling Cursor.getBlobn. It returns a byte array.

If the table entry is a content: URI, you should never try to open and read the file directly (for one thing, permissions problems can make this fail). Instead, you should call ContentResolver.openinputstreamn to get an InputStream object that you can use to read the data.

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