Question

I was using apple’s scrollview sample code PhotoScroller for my app using numerous images (and by recycling logic)
in UIScrollView. I implemented that in my app and it works fine.

Now Im working in an app similar to the above, but with the
difference, loading images in grid like view. When I happen to use the
same sample code, every thing works fine except the recycling logic.

I think there is some problem with my frame set which don’t tell the
xcode, the visible region.
Please some one temme how to set the visible set for the grid View
structure for scrollview? The code I use is,

CGRect visibleBounds = _scrollView.bounds;
// CGRect gridElementvisibleBounds = CGRectMake(0, 0, 212, 200);
int firstNeededPageIndex = floorf(CGRectGetMinX(visibleBounds) –
CGRectGetWidth(visibleBounds));
int lastNeededPageIndex = floorf((CGRectGetMaxX(visibleBounds)-1) –
CGRectGetWidth(visibleBounds));
firstNeededPageIndex = MAX(firstNeededPageIndex, 0);
lastNeededPageIndex = MIN(lastNeededPageIndex, [self imageCount] – 1);

where _scrollView is the UIScrollView instance that I use and the
gridElement that I use is of frame size (0, 0, 212, 200). The number
of grid elements that occupy the scrollView bounds is
3 x 3 (9).

I don’t want to use grid like tableViews(AQGridView, etc,.) since Im gonna load more than 500 images.
Please some one help me finding out the thing that I should correct in
the above code.

Answer 1

I nearly fixed the issue by making use of contentOffset to get the visible area.
Here is the piece of code illustrating what I did to make it working.

int firstNeededPageIndex = ((int)_scrollView.contentOffset.y / 960) * 9;
int lastNeededPageIndex = ((int)_scrollView.contentOffset.y / 960) * 9 + 17;

where I found the visible area by getting the contentOffset.y/960 and got the firstNeededPageIndex as given above.
When the scrollview scrolls, the components of the page that is getting to hide contains 9 elements and the successive page(got by lastNeededPageIndex) that is getting to be visible contains no components.
Hence I made it visible by making 18 objects to the visible area while scrolling.
Hence the objects to be visible while scrolling became 0th object to 17th object.

And the result is whenever the scrollview scrolls, 18 components(0 to 17) in the visible area(got through contentOffSet ) are recycled.