如何使UICollectionView具有无限分页? [英] How to make an UICollectionView with infinite paging?

问题描述

我有一个具有6个页面的UICollectionView，并启用了页面调度，还有一个UIPageControl.我想要的是，当我进入最后一页时，如果向右拖动，UICollectionView将无缝地从第一页重新加载.

I have a UICollectionView with 6 pages, and paging enabled, and a UIPageControl. What I want is, when I came to the last page, if I drag to right, UICollectionView reloads from first page seamlessly.

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

// The key is repositioning without animation
if (collectionView.contentOffset.x == 0) {
    // user is scrolling to the left from image 1 to image 10.
    // reposition offset to show image 10 that is on the right in the scroll view
    [collectionView scrollRectToVisible:CGRectMake(collectionView.frame.size.width*(pageControl.currentPage-1),0,collectionView.frame.size.width,collectionView.frame.size.height) animated:NO];
}
else if (collectionView.contentOffset.x == 1600) {
    // user is scrolling to the right from image 10 to image 1.
    // reposition offset to show image 1 that is on the left in the scroll view
    [collectionView scrollRectToVisible:CGRectMake(0,0,collectionView.frame.size.width,collectionView.frame.size.height) animated:NO];

}
pageControlUsed = NO;

}

它不像我想要的那样工作.我该怎么办?

It doesn't work like I want. What can I do?

推荐答案

我一直在使用Street Scroller示例为图像创建无限滚动器.直到我想对最近的IfNecessary代码进行pagingEnabled = YES;尝试调整，直到最终意识到，它是contentOffset.x才能与我希望在分页停止时可见的子视图的帧相匹配，才能正常工作.在recenterIfNecessary中，这实际上是行不通的，因为您无法知道将从layoutSubviews中调用它.如果您确实对其进行了调整，则子视图可能会从您的手指下面弹出.我在scrollViewDidEndDecelerating中进行调整.到目前为止，我还没有快速滚动的问题.即使pagingEnabled为NO，它也可以工作并模拟分页，但是使用YES看起来更自然.

I've been using the Street Scroller sample to create an infinite scroller for images. That works fine until I wanted to set pagingEnabled = YES; Tried tweaking around the recenterIfNecessary code and finally realized that it's the contentOffset.x that has to match the frame of the subview that i want visible when paging stops. This really isn't going to work in recenterIfNecessary since you have no way of knowing it will get called from layoutSubviews. If you do get it adjusted right, the subview may pop out from under your finger. I do the adjustment in scrollViewDidEndDecelerating. So far I haven't had problems with scrolling fast. It will work and simulate paging even when pagingEnabled is NO, but it looks more natural with YES.

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    [super scrollViewDidEndDecelerating:scrollView];

    CGPoint currentOffset = [self contentOffset];

    // find the subview that is the closest to the currentOffset.
    CGFloat closestOriginX = 999999;
    UIView *closestView = nil;
    for (UIView *v in self.visibleImageViews) {
        CGPoint origin = [self.imageContainerView convertPoint:v.frame.origin toView:self];
        CGFloat distanceToCurrentOffset = fabs(currentOffset.x - origin.x);
        if (distanceToCurrentOffset <= closestOriginX) {
            closestView = v;
            closestOriginX = distanceToCurrentOffset;
        }
    }

    // found the closest view, now find the correct offset
    CGPoint origin = [self.imageContainerView convertPoint:closestView.frame.origin toView:self];
    CGPoint center = [self.imageContainerView convertPoint:closestView.center toView:self];
    CGFloat offsetX = currentOffset.x - origin.x;

    // adjust the centers of the subviews
    [UIView animateWithDuration:0.1 animations:^{
        for (UIView *v in self.visibleImageViews) {
            v.center = [self convertPoint:CGPointMake(v.center.x+offsetX, center.y) toView:self.imageContainerView];
        }
    }];
}

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