sql - android cursor.moveToNext()?

Question

I am trying to query all the columns in a table into one long text view and/or string. I know this might not be the right way to do things but I have to do this. Correct me if I am wrong, I was under the impression that move next would get the next column in the row:

Cursor c = db.get();
if(c.moveToFirst){
do{
string = c.getString(0);
}while(c.moveToNext);

I thought that this would get the first column and display all of its contents instead I get the first column and first row. What am I doing wrong? Is there a better or real way to get this information without using a ListView?

Answer 1

The simple use is:

Cursor cursor = db.query(...);
while (cursor.moveToNext()) {
    ...
}

moveToFirst is used when you need to start iterating from start after you have already reached some position.

Avoid using cursor.getCount() except if it is required. And never use a loop over getCount().

getCount is expensive - it iterates over many records to count them. It doesn't return a stored variable. There may be some caching on a second call, but the first call doesn't know the answer until it is counted.

If your query matches 1000 rows, the cursor actually has only the first row. Each moveToNext searches and finds the next match. getCount must find all 1000. Why iterate over all if you only need 10? Why iterate twice?

Also, if your query doesn't use an index, getCount may be even slower - getCount may go over 10000 records even though the query matches only 100. Why loop 20000 instead of 10000?