Infinite UIScrollView not working on iOS 4.3 - objective-c

Question

I try to build a endless scrolling UIScrollView. So far I took the apple sample "StreetScroller". So all I do is setting the contentOffset back when it reaches the end of the scroll view.
Override -layoutSubviews of the UIScrollView:
- (void)layoutSubviews
{
CGFloat contentWidth = [self contentSize].width;
CGPoint contentOffset = [self contentOffset];
CGFloat centerOffsetX = (contentWidth - [self bounds].size.width) / 2.0;
CGFloat distanceFromCenter = contentOffset.x - centerOffsetX;
if (ABS(distanceFromCenter) > (contentWidth / 4.0)) {
contentOffset = CGPointMake(centerOffsetX, contentOffset.y);
[super setContentOffset:contentOffset];
}
}
Now on iOS 5 this works like a charm. But on iOS 4.3 it's not working. As soon as I call [super setContentOffset:contentOffset] it stoops scrolling because next time -layoutSubviews get's called the [self contentOffset] does not return the contentOffset that was set.
I know there are a lot a questions about infinite UIScrollViews, but one of these has fixed this problem!

Answer 1

Try this One. This Code is Working Properly for me on iOS 4.3
RootViewController.h
#class ViewControllerForDuplicateEndCaps;
#interface RootViewController : UIViewController {
ViewControllerForDuplicateEndCaps *viewControllerForDuplicateEndCaps;
}
#property (nonatomic, retain) ViewControllerForDuplicateEndCaps *viewControllerForDuplicateEndCaps;
- (IBAction)loadScrollViewWithDuplicateEndCaps:(id)sender;
#end
RootViewController.m
#import "RootViewController.h"
#import "ViewControllerForDuplicateEndCaps.h"
#import "InfiniteScrollViewAppDelegate.h"
#implementation RootViewController
#synthesize viewControllerForDuplicateEndCaps;
- (IBAction)loadScrollViewWithDuplicateEndCaps:(id)sender {
InfiniteScrollViewAppDelegate *delegate = (InfiniteScrollViewAppDelegate*)[[UIApplication sharedApplication] delegate];
if(self.viewControllerForDuplicateEndCaps == nil) {
ViewControllerForDuplicateEndCaps *temp = [[ViewControllerForDuplicateEndCaps alloc] initWithNibName:#"ViewControllerForDuplicateEndCaps" bundle:nil];
self.viewControllerForDuplicateEndCaps = temp;
[temp release];
}
UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:#"Back" style:UIBarButtonItemStyleBordered target:nil action:nil];
self.navigationItem.backBarButtonItem = backButton;
[backButton release];
[delegate.navigationController pushViewController:self.viewControllerForDuplicateEndCaps animated:YES];
}
- (void)dealloc {
[scrollView release];
[super dealloc];
}
#end
ViewControllerForDuplicateEndCaps.h
#import <UIKit/UIKit.h>
#interface ViewControllerForDuplicateEndCaps : UIViewController <UIScrollViewDelegate> {
IBOutlet UIScrollView *scrollView;
}
#property (nonatomic, retain) UIScrollView *scrollView;
- (void)addImageWithName:(NSString*)imageString atPosition:(int)position;
#end
ViewControllerForDuplicateEndCaps.m
#import "ViewControllerForDuplicateEndCaps.h"
#implementation ViewControllerForDuplicateEndCaps
#synthesize scrollView;
- (void)viewDidLoad {
[super viewDidLoad];
// add the last image (image4) into the first position
[self addImageWithName:#"image4.jpg" atPosition:0];
// add all of the images to the scroll view
for (int i = 1; i < 5; i++) {
[self addImageWithName:[NSString stringWithFormat:#"image%i.jpg",i] atPosition:i];
}
// add the first image (image1) into the last position
[self addImageWithName:#"image1.jpg" atPosition:5];
scrollView.contentSize = CGSizeMake(1920, 416);
[scrollView scrollRectToVisible:CGRectMake(320,0,320,416) animated:NO];
}
- (void)addImageWithName:(NSString*)imageString atPosition:(int)position {
// add image to scroll view
UIImage *image = [UIImage imageNamed:imageString];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
imageView.frame = CGRectMake(position*320, 0, 320, 416);
[scrollView addSubview:imageView];
[imageView release];
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)sender {
NSLog(#"%f",scrollView.contentOffset.x);
// The key is repositioning without animation
if (scrollView.contentOffset.x == 0) {
// user is scrolling to the left from image 1 to image 4
// reposition offset to show image 4 that is on the right in the scroll view
[scrollView scrollRectToVisible:CGRectMake(1280,0,320,416) animated:NO];
}
else if (scrollView.contentOffset.x == 1600) {
// user is scrolling to the right from image 4 to image 1
// reposition offset to show image 1 that is on the left in the scroll view
[scrollView scrollRectToVisible:CGRectMake(320,0,320,416) animated:NO];
}
}
- (void)dealloc {
[scrollView release];
[super dealloc];
}
#end