iOS

Question

我已经创建了这个包含 13 个图标的无限 collectionView 循环，但是它在 320 x 568 分辨率的设备上无法正常工作。问题在于滚动时计算适当的图像 contentOffset（这是一个动画 - 它不可触摸）并且一段时间后它不居中。这些图像之间的间距相等，因为我想一次在屏幕上显示 3 个图标。当 3 个图标通过 previousContentOffset 时，x = 319.5 应该是 x = 320.0 对于这种特殊情况，有什么解决方法的建议吗？也许通过单个图标迭代？我在 1 个图标幻灯片后得到的结果：

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];
}];
 }

Answer 1

我不久前实施了一个解决方法，所以我想我应该分享一下。我决定使用当前图标的索引而不是 contentOffset 进行迭代。我创建了一个 NSInteger 属性 currentIndex 并添加了计时器方法。

- (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 - collectionView contentOffset 中的 CGPoint 值不准确

iOS - inaccurate CGPoint value in collectionView contentOffset

scroll

objective-c

screen-resolution

uicollectionview