ios - UIScrollview の左右スワイプが正しくない

Question

ビューで写真を左右にスワイプするコードがいくつかあります。

#import "GalleryView.h"
#import "HotelDescription.h"
#import "GalleryImageView.h"

#define IMAGE_WIDTH     550
#define BORDER_WIDTH    15

#define IMAGE_WIDTH_IPHONE     320
#define BORDER_WIDTH_IPHONE    5

BOOL isRotating = NO;

@interface GalleryView (Private)
- (NSInteger)getCurrentPosition;
- (void)setNewPosition:(NSInteger)posIndex animated:(BOOL)animated;
@end

@implementation GalleryView
@synthesize scrollDelegate;

- (void)awakeFromNib
{
    [super awakeFromNib];
    self.delegate = self;
    self.pagingEnabled = NO;
    _galleryImageViews = [[NSMutableArray alloc] init];

    photoNum = 0;
}

- (void)setHotelDescription:(HotelDescription *)description
{
    [_hotelDescription release];
    _hotelDescription = [description retain];

    [_galleryImageViews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    [_galleryImageViews removeAllObjects];

    for (int i = 0; i < [_hotelDescription.imageURLs count]; i++)
    {
        GalleryImageView *giv;
        if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
            giv = [[GalleryImageView alloc] initWithFrame:CGRectMake(0, 0, IMAGE_WIDTH, IMAGE_WIDTH/1.5)];
        else
            giv = [[GalleryImageView alloc] initWithFrame:CGRectMake(0, 0, IMAGE_WIDTH_IPHONE, IMAGE_WIDTH_IPHONE/1.5)];

        [_galleryImageViews addObject:giv];
        [self addSubview:giv];
        [giv release];
    }

    [self setNewPosition:0 animated:NO];
}

- (void)updateImages
{
    for (GalleryImageView *giv in _galleryImageViews) 
    {
        if (giv.image == nil)
        {
            NSInteger index = [_galleryImageViews indexOfObject:giv];
            NSString *imageURL = [_hotelDescription.imageURLs objectAtIndex:index];
            NSString *filePath = [_hotelDescription filePathForImageURL:imageURL];

            if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) 
            {
                [giv setImage:[UIImage imageWithContentsOfFile:filePath]];
            }
        }
    }
}
// расположение картинок, задается их центр
- (void)updatePhotoPositions
{
    for (int i = 0; i < [_galleryImageViews count]; i++) 
    {
        CGFloat currentPhotoCenterOffset;

        if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
            currentPhotoCenterOffset = (BORDER_WIDTH * 2 + IMAGE_WIDTH) * i;
        else
            currentPhotoCenterOffset = (BORDER_WIDTH_IPHONE * 2 + IMAGE_WIDTH_IPHONE) * i;

        GalleryImageView *giv = [_galleryImageViews objectAtIndex:i];
        giv.center = CGPointMake(self.frame.size.width/2 + currentPhotoCenterOffset, self.frame.size.height / 2);
    }
}

- (void)layoutSubviews
{
    [super layoutSubviews];

    if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
    {
        CGFloat contentOffsetX = self.frame.size.width/2 - (IMAGE_WIDTH/2 + BORDER_WIDTH);
        [self setContentSize:CGSizeMake(contentOffsetX * 2 + [_galleryImageViews count] * (IMAGE_WIDTH + BORDER_WIDTH * 2), self.frame.size.height)];
        [self updatePhotoPositions];
    }
    else
    {
        CGFloat contentOffsetX = self.frame.size.width/2 - (IMAGE_WIDTH_IPHONE/2 + BORDER_WIDTH_IPHONE);
        [self setContentSize:CGSizeMake(contentOffsetX * 2 + [_galleryImageViews count] * (IMAGE_WIDTH_IPHONE + BORDER_WIDTH_IPHONE * 2), self.frame.size.height)];
        [self updatePhotoPositions];
    }

    if (isRotating)
        [self setNewPosition:_currentPosition animated:NO];
}

- (void)willRotate
{
    isRotating = YES;
}

- (void)didRotate
{
    isRotating = NO;
    [self setNewPosition:_currentPosition animated:NO];
}

#pragma mark - UIScrollView delegate

- (NSInteger)getCurrentPosition:(UIScrollView *)scrollView
{
    if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
    {
        ScrollDirection scrollDirection;
        NSLog(@"last = %d and new = %f", self.lastContentOffset, scrollView.contentOffset.x);
        if (self.lastContentOffset > scrollView.contentOffset.x)
        {
            scrollDirection = ScrollDirectionRight;
            if (photoNum != 0) {
                photoNum = photoNum - 1;
            }
            NSLog(@"Right = %d", photoNum);
        }
        else if (self.lastContentOffset < scrollView.contentOffset.x)
        {
            scrollDirection = ScrollDirectionLeft;
            if (photoNum != [_galleryImageViews count] -1) {
                photoNum = photoNum + 1;
            }
            NSLog(@"Left = %d", photoNum);
        }

        //self.lastContentOffset = scrollView.contentOffset.x;
        /*
        CGFloat imagesOffsetX = self.frame.size.width / 2 - (IMAGE_WIDTH /2 + BORDER_WIDTH);
        NSLog(@"1 = %f", imagesOffsetX);
        CGFloat photoOffset = self.contentOffset.x + self.frame.size.width / 2;
        NSLog(@"(%f + %f)", self.contentOffset.x, self.frame.size.width);
        NSLog(@"2 = %f", photoOffset);
        NSLog(@"(%f - %f)/(%d + %d * 2)", photoOffset, imagesOffsetX, IMAGE_WIDTH, BORDER_WIDTH);
        NSInteger index = (photoOffset - imagesOffsetX) / (IMAGE_WIDTH + BORDER_WIDTH * 2);
        NSLog(@"3 = %d", index);
        index = MAX(index, 0);
        index = MIN(index, [_galleryImageViews count]-1);
        return index;
         */
        NSLog(@"phNum = %d", photoNum);
        return photoNum;
    }
    else
    {
        CGFloat imagesOffsetX = self.frame.size.width / 2 - (IMAGE_WIDTH_IPHONE /2 + BORDER_WIDTH_IPHONE);
        CGFloat photoOffset = self.contentOffset.x + self.frame.size.width / 2;
        NSInteger index = (photoOffset - imagesOffsetX) / (IMAGE_WIDTH_IPHONE + BORDER_WIDTH_IPHONE * 2);
        index = MAX(index, 0);
        index = MIN(index, [_galleryImageViews count]-1);
        return index;
    }
}

- (void)setNewPosition:(NSInteger)posIndex animated:(BOOL)animated
{
    _currentPosition = posIndex;

    if ([UIDevice currentDevice].userInterfaceIdiom == UIUserInterfaceIdiomPad)
    {
        CGFloat currentPhotoCenterOffset = (BORDER_WIDTH * 2 + IMAGE_WIDTH) * _currentPosition;
        [self setContentOffset:CGPointMake(currentPhotoCenterOffset, self.contentOffset.y) animated:animated];
    }
    else
    {
        CGFloat currentPhotoCenterOffset = (BORDER_WIDTH_IPHONE * 2 + IMAGE_WIDTH_IPHONE) * _currentPosition;
        [self setContentOffset:CGPointMake(currentPhotoCenterOffset, self.contentOffset.y) animated:animated];
    }

    if (scrollDelegate)
        [scrollDelegate galleryView:self didSelectPhotoNo:posIndex];
}
//начинает обрабатывать движения
-(void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
{
    [scrollView setContentOffset:scrollView.contentOffset animated:NO];
    self.lastContentOffset = scrollView.contentOffset.x;
    [self setNewPosition:[self getCurrentPosition:scrollView] animated:YES];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
    [self setNewPosition:[self getCurrentPosition:scrollView] animated:YES];
}
#pragma mark - Memory management

- (void)dealloc 
{
    [_galleryImageViews release];
    [_hotelDescription release];
    [super dealloc];
}

@end

しかし、私にはいくつかのバグがあります(左にスワイプします-大丈夫ですが、右にスワイプしようとすると、写真はまだ左にジャンプします(リストの最後に到達するまで続きます。反対方向には同じバグ(

どこが間違っていたのですか？