iOS - collection中的CGPoint值不准确查看内容偏移

问题描述：

我已经创建了这个无限的具有13个图标的collectionView循环，但它在320 x 568分辨率设备上无法正常工作。问题是在滚动时计算适当的图像contentOffset（这是一个动画 - 它不可触摸），并且它在一段时间后不居中。这些图像间隔相等，因为我想一次在屏幕上显示3个图标。当3个图标通过时，previousContentOffset是x = 319.5，它应该是x = 320.0对于这种特殊情况的任何解决方法建议？也许迭代单个图标？结果，我后1个图标滑动获得：iOS - collection中的CGPoint值不准确查看内容偏移

previousContentOffset =（CGPoint）（X = 106.5，Y = 0），
宽度=（双）106.66666666666667，
currentContentOffset = （CGPoint）（X = 213.16666666666669，Y = 0）

//无限循环

- (void)setupDataForCollectionView { 

NSArray *originalArray = self.arrayImages; 

NSMutableArray *workingArray = [originalArray mutableCopy]; 

self.dataArray = [workingArray mutableCopy]; 
} 

// Implementation of infinite loop 

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { 

// calculate width for every device 

double contentOffsetWhenFullyScrolledRight = self.collectionViewHorizontal.contentSize.width - self.collectionViewHorizontal.frame.size.width; 

if (scrollView.contentOffset.x == contentOffsetWhenFullyScrolledRight) { 

    NSIndexPath *newIndexPath = [NSIndexPath indexPathForItem:1 inSection:0]; 

    [self.collectionViewHorizontal scrollToItemAtIndexPath:newIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:NO]; 

} else if (scrollView.contentOffset.x == 0) { 

    NSIndexPath *newIndexPath = [NSIndexPath indexPathForItem:([self.dataArray count] -2) inSection:0]; 

    [self.collectionViewHorizontal scrollToItemAtIndexPath:newIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:NO]; 
    } 
} 

// TimeInterval for animation 

- (void)timerAction:(NSTimer *)timer { 

//previous icon content offset 
CGPoint previousContentOffSet = self.collectionViewHorizontal.contentOffset; 

//next icon width 
double width = self.collectionViewHorizontal.frame.size.width/3; 
// NSUInteger index = (int)(floor(self.collectionViewHorizontal.contentOffset.x/width) + 1); 

// animate icons scroll view 
CGPoint currentContentOffset = CGPointMake(previousContentOffSet.x + width, previousContentOffSet.y); 

NSIndexPath *indexPath = [self.collectionViewHorizontal indexPathForItemAtPoint:currentContentOffset]; 
if (indexPath.row > self.dataArray.count - 4) { 
    // add elements and reload 
    [self.dataArray addObjectsFromArray:[self.arrayImages copy]]; 
    [self.collectionViewHorizontal reloadData]; 
} 
// sliding animation 
[UIView animateWithDuration:.3 delay:.0 usingSpringWithDamping:0.5 initialSpringVelocity:.0 options:kNilOptions animations:^{ 
    self.collectionViewHorizontal.contentOffset = currentContentOffset; 
} completion:^(BOOL finished) { 
    [self scrollViewDidEndDecelerating:self.collectionViewHorizontal]; 
}]; 
}

答

我已经实施了一种解决方法，所以我想我应该分享。我决定迭代当前图标的索引而不是contentOffset。我已经创建了一个NSInteger属性currentIndex并添加到定时器方法中。

- (void)timerAction:(NSTimer *)timer { 

self.currentIndex++; 

//next icon width 
double width = self.collectionViewHorizontal.frame.size.width/3; 

// animate icons scroll view 
CGPoint currentContentOffset = CGPointMake(self.currentIndex * width, 0.0); 

NSIndexPath *indexPath = [self.collectionViewHorizontal indexPathForItemAtPoint:currentContentOffset]; 
if (indexPath.row > (self.dataArray.count /2) { 
    // add elements and reload 
    [self.dataArray addObjectsFromArray:[self.arrayImages copy]]; 
    [self.collectionViewHorizontal reloadData]; 
} 
// sliding animation 
[UIView animateWithDuration:.3 delay:.0 usingSpringWithDamping:0.5 initialSpringVelocity:.0 options:kNilOptions animations:^{ 
    self.collectionViewHorizontal.contentOffset = currentContentOffset; 
} completion:^(BOOL finished) { 
    [self scrollViewDidEndDecelerating:self.collectionViewHorizontal]; 
}]; 
}

iOS - collection中的CGPoint值不准确查看内容偏移

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