Question

我需要在UICollectionView中显示3个项目，并启用这样的分页

enter image description here

但我变得像这样 enter image description here

我已经制作了自定义流程，加上分页已启用但无法获得我需要的内容。我怎样才能实现这一点，或者我应该调查哪个代表，或者指导我从哪里获得有关此方案的帮助。

- (void)awakeFromNib
{
    self.itemSize = CGSizeMake(480, 626);
    self.minimumInteritemSpacing = 112;
    self.minimumLineSpacing = 112;
    self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    self.sectionInset = UIEdgeInsetsMake(0, 272, 0, 272);
}

Answer 1

修改：演示链接：https://github.com/raheelsadiq/UICollectionView-horizontal-paging-with-3-items

经过大量搜索我做到了，找到下一个要滚动的点并禁用分页。在scrollviewWillEndDragging中滚动到下一个单元格x。

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset { float pageWidth = 480 + 50; // width + space float currentOffset = scrollView.contentOffset.x; float targetOffset = targetContentOffset->x; float newTargetOffset = 0; if (targetOffset > currentOffset) newTargetOffset = ceilf(currentOffset / pageWidth) * pageWidth; else newTargetOffset = floorf(currentOffset / pageWidth) * pageWidth; if (newTargetOffset < 0) newTargetOffset = 0; else if (newTargetOffset > scrollView.contentSize.width) newTargetOffset = scrollView.contentSize.width; targetContentOffset->x = currentOffset; [scrollView setContentOffset:CGPointMake(newTargetOffset, scrollView.contentOffset.y) animated:YES]; }

我还必须使左右小而中心大，所以我用变换做了。问题在于找到索引，因此很难找到。

对于在同一方法中左右变换，请使用newTargetOffset

int index = newTargetOffset / pageWidth; if (index == 0) { // If first index UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:[NSIndexPath indexPathForItem:index inSection:0]]; [UIView animateWithDuration:ANIMATION_SPEED animations:^{ cell.transform = CGAffineTransformIdentity; }]; cell = [self.collectionView cellForItemAtIndexPath:[NSIndexPath indexPathForItem:index + 1 inSection:0]]; [UIView animateWithDuration:ANIMATION_SPEED animations:^{ cell.transform = TRANSFORM_CELL_VALUE; }]; }else{ UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:[NSIndexPath indexPathForItem:index inSection:0]]; [UIView animateWithDuration:ANIMATION_SPEED animations:^{ cell.transform = CGAffineTransformIdentity; }]; index --; // left cell = [self.collectionView cellForItemAtIndexPath:[NSIndexPath indexPathForItem:index inSection:0]]; [UIView animateWithDuration:ANIMATION_SPEED animations:^{ cell.transform = TRANSFORM_CELL_VALUE; }]; index ++; index ++; // right cell = [self.collectionView cellForItemAtIndexPath:[NSIndexPath indexPathForItem:index inSection:0]]; [UIView animateWithDuration:ANIMATION_SPEED animations:^{ cell.transform = TRANSFORM_CELL_VALUE; }]; }

在cellForRowAtIndex中添加

if (indexPath.row == 0 && isfirstTimeTransform) { // make a bool and set YES initially, this check will prevent fist load transform isfirstTimeTransform = NO; }else{ cell.transform = TRANSFORM_CELL_VALUE; // the new cell will always be transform and without animation }

添加这两个宏，或者您希望同时处理这两个宏

#define TRANSFORM_CELL_VALUE CGAffineTransformMakeScale(0.8, 0.8) #define ANIMATION_SPEED 0.2

最终结果是

Answer 2

@Raheel Sadiq 的第一部分在 Swift 3 中回答，没有变换。

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        let pageWidth: Float = Float(self.collectionView.frame.width / 3) //480 + 50
        // width + space
        let currentOffset: Float = Float(scrollView.contentOffset.x)
        let targetOffset: Float = Float(targetContentOffset.pointee.x)
        var newTargetOffset: Float = 0
        if targetOffset > currentOffset {
            newTargetOffset = ceilf(currentOffset / pageWidth) * pageWidth
        }
        else {
            newTargetOffset = floorf(currentOffset / pageWidth) * pageWidth
        }
        if newTargetOffset < 0 {
            newTargetOffset = 0
        }
        else if (newTargetOffset > Float(scrollView.contentSize.width)){
            newTargetOffset = Float(Float(scrollView.contentSize.width))
        }

        targetContentOffset.pointee.x = CGFloat(currentOffset)
        scrollView.setContentOffset(CGPoint(x: CGFloat(newTargetOffset), y: scrollView.contentOffset.y), animated: true)

    }

Answer 3

Swift 3.0 基于Raheel Sadiq

的完整解决方案

var isfirstTimeTransform:Bool = true

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {


    let cell : UICollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "YourCustomViewCell", for: indexPath)

    if (indexPath.row == 0 && isfirstTimeTransform) { 
        isfirstTimeTransform = false
    }else{
        cell.transform = CGAffineTransform(scaleX: 0.8, y: 0.8) 
    }

    return cell
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

    return CGSize(width: collectionView.bounds.width/3, height: collectionView.bounds.height)
}

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    // Simulate "Page" Function
    let pageWidth: Float = Float(self.collectionView.frame.width/3 + 20)
    let currentOffset: Float = Float(scrollView.contentOffset.x)
    let targetOffset: Float = Float(targetContentOffset.pointee.x)
    var newTargetOffset: Float = 0
    if targetOffset > currentOffset {
        newTargetOffset = ceilf(currentOffset / pageWidth) * pageWidth
    }
    else {
        newTargetOffset = floorf(currentOffset / pageWidth) * pageWidth
    }
    if newTargetOffset < 0 {
        newTargetOffset = 0
    }
    else if (newTargetOffset > Float(scrollView.contentSize.width)){
        newTargetOffset = Float(Float(scrollView.contentSize.width))
    }

    targetContentOffset.pointee.x = CGFloat(currentOffset)
    scrollView.setContentOffset(CGPoint(x: CGFloat(newTargetOffset), y: scrollView.contentOffset.y), animated: true)

    // Make Transition Effects for cells
    let duration = 0.2
    var index = newTargetOffset / pageWidth;
    var cell:UICollectionViewCell = self.collectionView.cellForItem(at: IndexPath(row: Int(index), section: 0))!
    if (index == 0) { // If first index
        UIView.animate(withDuration: duration, delay: 0.0, options: [ .curveEaseOut], animations: {
            cell.transform = CGAffineTransform.identity
        }, completion: nil)
        index += 1
        cell = self.collectionView.cellForItem(at: IndexPath(row: Int(index), section: 0))!
        UIView.animate(withDuration: duration, delay: 0.0, options: [ .curveEaseOut], animations: {
            cell.transform = CGAffineTransform(scaleX: 0.8, y: 0.8)
        }, completion: nil)
    }else{
        UIView.animate(withDuration: duration, delay: 0.0, options: [ .curveEaseOut], animations: {
            cell.transform = CGAffineTransform.identity;
        }, completion: nil)

        index -= 1 // left
        if let cell = self.collectionView.cellForItem(at: IndexPath(row: Int(index), section: 0)) {
            UIView.animate(withDuration: duration, delay: 0.0, options: [ .curveEaseOut], animations: {
                cell.transform = CGAffineTransform(scaleX: 0.8, y: 0.8);
            }, completion: nil)
        }

        index += 1
        index += 1 // right
        if let cell = self.collectionView.cellForItem(at: IndexPath(row: Int(index), section: 0)) {
            UIView.animate(withDuration: duration, delay: 0.0, options: [ .curveEaseOut], animations: {
                cell.transform = CGAffineTransform(scaleX: 0.8, y: 0.8);
            }, completion: nil)
        }
    }

}

Answer 4

我认为，@ raheel-sadiq答案很棒，但很难理解。在我看来，这是一个非常易读的版本：

 func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint,
                                   targetContentOffset: UnsafeMutablePointer<CGPoint>) {

        //minimumLineSpacing and insetForSection are two constants in my code

        //this cell width is for my case, adapt to yours
        let cellItemWidth = view.frame.width - (insetForSection.left + insetForSection.right)
        let pageWidth = Float(cellItemWidth + minimumLineSpacing)

        let offsetXAfterDragging = Float(scrollView.contentOffset.x)
        let targetOffsetX = Float(targetContentOffset.pointee.x)

        let pagesCountForOffset = pagesCount(forOffset: offsetXAfterDragging, withTargetOffset: targetOffsetX, pageWidth: pageWidth)

        var newTargetOffsetX = pagesCountForOffset * pageWidth

        keepNewTargetInBounds(&newTargetOffsetX, scrollView)

        //ignore target
        targetContentOffset.pointee.x = CGFloat(offsetXAfterDragging)

        let newTargetPoint = CGPoint(x: CGFloat(newTargetOffsetX), y: scrollView.contentOffset.y)
        scrollView.setContentOffset(newTargetPoint, animated: true)

        //if you're using pageControl
        pageControl.currentPage = Int(newTargetOffsetX / pageWidth)

    }

    fileprivate func pagesCount(forOffset offset: Float, withTargetOffset targetOffset: Float, pageWidth: Float) -> Float {
        let isRightDirection = targetOffset > offset
        let roundFunction = isRightDirection ? ceilf : floorf
        let pagesCountForOffset = roundFunction(offset / pageWidth)
        return pagesCountForOffset
    }

    fileprivate func keepNewTargetInBounds(_ newTargetOffsetX: inout Float, _ scrollView: UIScrollView) {
        if newTargetOffsetX < 0 { newTargetOffsetX = 0 }
        let contentSizeWidth = Float(scrollView.contentSize.width)
        if newTargetOffsetX > contentSizeWidth { newTargetOffsetX = contentSizeWidth }
    }

Answer 5

您必须覆盖流布局的 targetContentOffsetForProposedContentOffset：withScrollingVelocity：方法。这样就可以捕捉滚动视图的停止点。

-(CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity
{
    CGFloat yOffset = MAXFLOAT;

    CGRect proposedRect;
    proposedRect.origin = proposedContentOffset;
    proposedRect.size = self.collectionView.bounds.size;
    CGPoint proposedCenterPoint = CGPointMake(CGRectGetMidX(proposedRect), CGRectGetMidY(proposedRect)) ;

    NSArray *array = [super layoutAttributesForElementsInRect:proposedRect];

    for (UICollectionViewLayoutAttributes *attributes in array)
    {
        CGFloat newOffset = attributes.center.y - proposedCenterPoint.y;
        if ( fabsf(newOffset) < fabs(yOffset))
        {
            yOffset = newOffset;
        }
    }

    return CGPointMake(proposedContentOffset.x, proposedContentOffset.y + yOffset);
}

此外，您还需要设置流布局的sectionInset以使第一个单元格和最后一个单元格居中。我的例子是高度，但很容易切换到宽度。

CGFloat height = (self.collectionView.bounds.size.height / 2.0 ) - (self.itemSize.height / 2.0) ;
self.sectionInset = UIEdgeInsetsMake(height, 30.0, height, 30.0) ;

Answer 6

我的水平集合视图分页解决方案

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    if scrollView == collectionView { collectionView.scrollToPage() }
}

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    if scrollView == collectionView { if !decelerate { collectionView.scrollToPage() } }
}

以及collectionView的小扩展

public func scrollToPage() {
    var currentCellOffset = contentOffset
    currentCellOffset.x += width / 2
    var path = indexPathForItem(at: currentCellOffset)
    if path == nil {
        currentCellOffset.x += 15
        path = indexPathForItem(at: currentCellOffset)
    }
    if path != nil {
        scrollToItem(at: path!, at: .centeredHorizontally, animated: true)
    }
}

UICollectionView水平分页有3个项目

6 个答案: