android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0

Question

I am using custom adapter extending cursor adapter for displaying data in listview, to display particular phone number i have passed the id to a method in database class but it is showing

errorandroid.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0 

while placing debugger in the the method it is not going after the line

num = cursor.getString(cursor.getColumnIndex("ContactNumber"));

Can any one help me to solve it. This is the code:

public String getNumberFromId(int id) 
{
    String num;
    db= this.getReadableDatabase();
    Cursor cursor = db.query(scheduletable, new String[] { "ContactNumber" },"_id="+id, null, null, null, null);
    cursor.moveToFirst();
    num = cursor.getString(cursor.getColumnIndex("ContactNumber")); 
    cursor.close();
    db.close();
    return num;
}

Answer 1

Whenever you are dealing with Cursors, ALWAYS check for null and check for moveToFirst() without fail.

if( cursor != null && cursor.moveToFirst() ){
    num = cursor.getString(cursor.getColumnIndex("ContactNumber"));
    cursor.close(); 
}

Place logs appropriately to see whether it is returning null or an empty cursor. According to that check your query.

Update Put both the checks in a single statement as mentioned by Jon in the comment below.

Update 2 Put the close() call within the valid cursor scope.