Question

我尝试构建一个无休止的滚动UIScrollView。到目前为止，我拿了苹果样本“StreetScroller”。所以我所做的就是在到达滚动视图的末尾时将contentOffset设置回来。

覆盖UIScrollView的-layoutSubviews：

- (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];
    }
}

现在在iOS 5上，这就像一个魅力。但是在iOS 4.3上它没有用。一旦我调用[super setContentOffset:contentOffset]，它就会停止滚动，因为下次调用-layoutSubviews时，[self contentOffset]不会返回已设置的contentOffset。

我知道有很多关于无限UIScrollViews的问题，但其中一个已经解决了这个问题！

Answer 1

试试这个。此代码在iOS 4.3上正式适用于我

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

无限UIScrollView无法在iOS 4.3上运行

1 个答案: