What's the best way to iterate an Android Curs

Question

I frequently see code which involves iterating over the result of a database query, doing something with each row, and then moving on to the next row. Typical examples are as follows.

Cursor cursor = db.rawQuery(...);
cursor.moveToFirst();
while (cursor.isAfterLast() == false) 
{
    ...
    cursor.moveToNext();
}

Cursor cursor = db.rawQuery(...);
for (boolean hasItem = cursor.moveToFirst(); 
     hasItem; 
     hasItem = cursor.moveToNext()) {
    ...
}

Cursor cursor = db.rawQuery(...);
if (cursor.moveToFirst()) {
    do {
        ...                 
    } while (cursor.moveToNext());
}

These all seem excessively long-winded to me, each with multiple calls to Cursor methods. Surely there must be a neater way?

Answer 1

Initially cursor is not on the first row show using moveToNext() you can iterate the cursor when record is not exist then it return false,unless it return true,

while (cursor.moveToNext()) {
    ...
}

Answer 2

if (cursor.getCount() == 0)
  return;

cursor.moveToFirst();

while (!cursor.isAfterLast())
{
  // do something
  cursor.moveToNext();
}

cursor.close();

Answer 3

The Do/While solution is more elegant, but if you do use just the While solution posted above, without the moveToPosition(-1) you will miss the first element (at least on the Contact query).

I suggest:

if (cursor.getCount() > 0) {
    cursor.moveToPosition(-1);
    while (cursor.moveToNext()) {
          <do stuff>
    }
}

Answer 4

I'd just like to point out a third alternative which also works if the cursor is not at the start position:

if (cursor.moveToFirst()) {
    do {
        // do what you need with the cursor here
    } while (cursor.moveToNext());
}

Answer 5

The best looking way I've found to go through a cursor is the following:

Cursor cursor;
... //fill the cursor here

for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {
    // do what you need with the cursor here
}

Don't forget to close the cursor afterwards

EDIT: The given solution is great if you ever need to iterate a cursor that you are not responsible for. A good example would be, if you are taking a cursor as argument in a method, and you need to scan the cursor for a given value, without having to worry for the cursor's current position.

Answer 6

Below could be the better way:

if (cursor.moveToFirst()) {
   while (!cursor.isAfterLast()) {
         //your code to implement
         cursor.moveToNext();
    }
}
cursor.close();

The above code would insure that it would go through entire iteration and won't escape first and last iteration.