UICollectionView水平分页 - 我可以使用Flow Layout吗？

Question

这与To use Flow Layout, or to Customize?有所不同。

以下是我正在尝试做的事情的说明：

我想知道我是否可以使用UICollectionViewFlowLayout，它的子类，或者如果我需要创建一个完全自定义的布局？根据UICollectionView上的WWDC 2012视频，如果您使用垂直滚动的Flow Layout，您的布局线条是水平的，如果您水平滚动，您的布局线条是垂直的。我想在水平滚动的集合视图中使用水平布局线。

我的模型中也没有固有的部分 - 这只是一组项目。我可以将它们分成几个部分，但是集合视图是可调整大小的，因此可以适应页面的项目数量有时会发生变化，看起来每个项目所在的页面的选择最好留给布局而不是如果我没有任何有意义的部分，该模型。

那么，我可以使用Flow Layout执行此操作，还是需要创建自定义布局？

Answer 1

在这里，我分享我的简单实现！

.h文件：

/** 
 * CollectionViewLayout for an horizontal flow type:
 *
 *  |   0   1   |   6   7   |
 *  |   2   3   |   8   9   |   ----> etc...
 *  |   4   5   |   10  11  |
 *
 * Only supports 1 section and no headers, footers or decorator views.
 */
@interface HorizontalCollectionViewLayout : UICollectionViewLayout

@property (nonatomic, assign) CGSize itemSize;

@end

.m文件：

@implementation HorizontalCollectionViewLayout
{
    NSInteger _cellCount;
    CGSize _boundsSize;
}

- (void)prepareLayout
{
    // Get the number of cells and the bounds size
    _cellCount = [self.collectionView numberOfItemsInSection:0];
    _boundsSize = self.collectionView.bounds.size;
}

- (CGSize)collectionViewContentSize
{
    // We should return the content size. Lets do some math:

    NSInteger verticalItemsCount = (NSInteger)floorf(_boundsSize.height / _itemSize.height);
    NSInteger horizontalItemsCount = (NSInteger)floorf(_boundsSize.width / _itemSize.width);

    NSInteger itemsPerPage = verticalItemsCount * horizontalItemsCount;
    NSInteger numberOfItems = _cellCount;
    NSInteger numberOfPages = (NSInteger)ceilf((CGFloat)numberOfItems / (CGFloat)itemsPerPage);

    CGSize size = _boundsSize;
    size.width = numberOfPages * _boundsSize.width;
    return size;
}

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    // This method requires to return the attributes of those cells that intsersect with the given rect.
    // In this implementation we just return all the attributes.
    // In a better implementation we could compute only those attributes that intersect with the given rect.

    NSMutableArray *allAttributes = [NSMutableArray arrayWithCapacity:_cellCount];

    for (NSUInteger i=0; i<_cellCount; ++i)
    {
        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:i inSection:0];
        UICollectionViewLayoutAttributes *attr = [self _layoutForAttributesForCellAtIndexPath:indexPath];

        [allAttributes addObject:attr];
    }

    return allAttributes;
}

- (UICollectionViewLayoutAttributes*)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return [self _layoutForAttributesForCellAtIndexPath:indexPath];
}

- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
    // We should do some math here, but we are lazy.
    return YES;
}

- (UICollectionViewLayoutAttributes*)_layoutForAttributesForCellAtIndexPath:(NSIndexPath*)indexPath
{
    // Here we have the magic of the layout.

    NSInteger row = indexPath.row;

    CGRect bounds = self.collectionView.bounds;
    CGSize itemSize = self.itemSize;

    // Get some info:
    NSInteger verticalItemsCount = (NSInteger)floorf(bounds.size.height / itemSize.height);
    NSInteger horizontalItemsCount = (NSInteger)floorf(bounds.size.width / itemSize.width);
    NSInteger itemsPerPage = verticalItemsCount * horizontalItemsCount;

    // Compute the column & row position, as well as the page of the cell.
    NSInteger columnPosition = row%horizontalItemsCount;
    NSInteger rowPosition = (row/horizontalItemsCount)%verticalItemsCount;
    NSInteger itemPage = floorf(row/itemsPerPage);

    // Creating an empty attribute
    UICollectionViewLayoutAttributes *attr = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];

    CGRect frame = CGRectZero;

    // And finally, we assign the positions of the cells
    frame.origin.x = itemPage * bounds.size.width + columnPosition * itemSize.width;
    frame.origin.y = rowPosition * itemSize.height;
    frame.size = _itemSize;

    attr.frame = frame;

    return attr;
}

#pragma mark Properties

- (void)setItemSize:(CGSize)itemSize
{
    _itemSize = itemSize;
    [self invalidateLayout];
}

@end

最后，如果你想要一个分页行为，你只需要配置你的UICollectionView：

_collectionView.pagingEnabled = YES;

希望足够有用。

Answer 2

将vilanovi代码转换为Swift，万一有人，将来需要它。

public class HorizontalCollectionViewLayout : UICollectionViewLayout {
private var cellWidth = 90 // Don't kow how to get cell size dynamically
private var cellHeight = 90

public override func prepareLayout() {
}

public override func collectionViewContentSize() -> CGSize {
    let numberOfPages = Int(ceilf(Float(cellCount) / Float(cellsPerPage)))
    let width = numberOfPages * Int(boundsWidth)
    return CGSize(width: CGFloat(width), height: boundsHeight)
}

public override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject]? {
    var allAttributes = [UICollectionViewLayoutAttributes]()

    for (var i = 0; i < cellCount; ++i) {
        let indexPath = NSIndexPath(forRow: i, inSection: 0)
        let attr = createLayoutAttributesForCellAtIndexPath(indexPath)
        allAttributes.append(attr)
    }

    return allAttributes
}

public override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes! {
    return createLayoutAttributesForCellAtIndexPath(indexPath)
}

public override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
    return true
}

private func createLayoutAttributesForCellAtIndexPath(indexPath:NSIndexPath)
    -> UICollectionViewLayoutAttributes {
        let layoutAttributes = UICollectionViewLayoutAttributes(forCellWithIndexPath: indexPath)
        layoutAttributes.frame = createCellAttributeFrame(indexPath.row)
        return layoutAttributes
}

private var boundsWidth:CGFloat {
    return self.collectionView!.bounds.size.width
}

private var boundsHeight:CGFloat {
    return self.collectionView!.bounds.size.height
}

private var cellCount:Int {
    return self.collectionView!.numberOfItemsInSection(0)
}

private var verticalCellCount:Int {
    return Int(floorf(Float(boundsHeight) / Float(cellHeight)))
}

private var horizontalCellCount:Int {
    return Int(floorf(Float(boundsWidth) / Float(cellWidth)))
}

private var cellsPerPage:Int {
    return verticalCellCount * horizontalCellCount
}

private func createCellAttributeFrame(row:Int) -> CGRect {
    let frameSize = CGSize(width:cellWidth, height: cellHeight )
    let frameX = calculateCellFrameHorizontalPosition(row)
    let frameY = calculateCellFrameVerticalPosition(row)
    return CGRectMake(frameX, frameY, frameSize.width, frameSize.height)
}

private func calculateCellFrameHorizontalPosition(row:Int) -> CGFloat {
    let columnPosition = row % horizontalCellCount
    let cellPage = Int(floorf(Float(row) / Float(cellsPerPage)))
    return CGFloat(cellPage * Int(boundsWidth) + columnPosition * Int(cellWidth))
}

private func calculateCellFrameVerticalPosition(row:Int) -> CGFloat {
    let rowPosition = (row / horizontalCellCount) % verticalCellCount
    return CGFloat(rowPosition * Int(cellHeight))
}

}

Answer 3

你是对的 - 这不是股票横向滚动集合视图如何布局单元格。我担心你将不得不实现自己的自定义UICollectionViewLayout子类。要么是这样，要么将模型分成几个部分。

Answer 4

前面的上述实现并不完整，错误，并且具有固定的单元大小。这是代码的更直译：

import UIKit

class HorizontalFlowLayout: UICollectionViewLayout {
    var itemSize = CGSizeZero {
        didSet {
            invalidateLayout()
        }
    }
    private var cellCount = 0
    private var boundsSize = CGSizeZero

    override func prepareLayout() {
        cellCount = self.collectionView!.numberOfItemsInSection(0)
        boundsSize = self.collectionView!.bounds.size
    }

    override func collectionViewContentSize() -> CGSize {
        let verticalItemsCount = Int(floor(boundsSize.height / itemSize.height))
        let horizontalItemsCount = Int(floor(boundsSize.width / itemSize.width))

        let itemsPerPage = verticalItemsCount * horizontalItemsCount
        let numberOfItems = cellCount
        let numberOfPages = Int(ceil(Double(numberOfItems) / Double(itemsPerPage)))

        var size = boundsSize
        size.width = CGFloat(numberOfPages) * boundsSize.width
        return size
    }

    override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        var allAttributes = [UICollectionViewLayoutAttributes]()
        for var i = 0; i < cellCount; i++ {
            let indexPath = NSIndexPath(forRow: i, inSection: 0)
            let attr = self.computeLayoutAttributesForCellAtIndexPath(indexPath)
            allAttributes.append(attr)
        }
        return allAttributes
    }

    override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
        return self.computeLayoutAttributesForCellAtIndexPath(indexPath)
    }

    override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
        return true
    }

    func computeLayoutAttributesForCellAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes {
        let row = indexPath.row
        let bounds = self.collectionView!.bounds

        let verticalItemsCount = Int(floor(boundsSize.height / itemSize.height))
        let horizontalItemsCount = Int(floor(boundsSize.width / itemSize.width))
        let itemsPerPage = verticalItemsCount * horizontalItemsCount

        let columnPosition = row % horizontalItemsCount
        let rowPosition = (row/horizontalItemsCount)%verticalItemsCount
        let itemPage = Int(floor(Double(row)/Double(itemsPerPage)))

        let attr = UICollectionViewLayoutAttributes(forCellWithIndexPath: indexPath)

        var frame = CGRectZero
        frame.origin.x = CGFloat(itemPage) * bounds.size.width + CGFloat(columnPosition) * itemSize.width
        frame.origin.y = CGFloat(rowPosition) * itemSize.height
        frame.size = itemSize
        attr.frame = frame

        return attr
    }
}

Answer 5

Swift 4

代码：

public class HorizontalFlowLayout: UICollectionViewLayout {
    var itemSize = CGSize(width: 0, height: 0) {
        didSet {
            invalidateLayout()
        }
    }
    private var cellCount = 0
    private var boundsSize = CGSize(width: 0, height: 0)

    public override func prepare() {
        cellCount = self.collectionView!.numberOfItems(inSection: 0)
        boundsSize = self.collectionView!.bounds.size
    }
    public override var collectionViewContentSize: CGSize {
        let verticalItemsCount = Int(floor(boundsSize.height / itemSize.height))
        let horizontalItemsCount = Int(floor(boundsSize.width / itemSize.width))

        let itemsPerPage = verticalItemsCount * horizontalItemsCount
    let numberOfItems = cellCount
    let numberOfPages = Int(ceil(Double(numberOfItems) / Double(itemsPerPage)))

        var size = boundsSize
        size.width = CGFloat(numberOfPages) * boundsSize.width
        return size
    }

    public override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        var allAttributes = [UICollectionViewLayoutAttributes]()
        for i in 0...(cellCount-1) {
            let indexPath = IndexPath(row: i, section: 0)
            let attr = self.computeLayoutAttributesForCellAt(indexPath: indexPath)
            allAttributes.append(attr)
        }
        return allAttributes
    }

    public override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        return computeLayoutAttributesForCellAt(indexPath: indexPath)
    }

    public override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true
    }

    private func computeLayoutAttributesForCellAt(indexPath:IndexPath)
        -> UICollectionViewLayoutAttributes {
            let row = indexPath.row
            let bounds = self.collectionView!.bounds

            let verticalItemsCount = Int(floor(boundsSize.height / itemSize.height))
            let horizontalItemsCount = Int(floor(boundsSize.width / itemSize.width))
            let itemsPerPage = verticalItemsCount * horizontalItemsCount

            let columnPosition = row % horizontalItemsCount
            let rowPosition = (row/horizontalItemsCount)%verticalItemsCount
            let itemPage = Int(floor(Double(row)/Double(itemsPerPage)))

            let attr = UICollectionViewLayoutAttributes(forCellWith: indexPath)

            var frame = CGRect(x: 0, y: 0, width: 0, height: 0)
            frame.origin.x = CGFloat(itemPage) * bounds.size.width + CGFloat(columnPosition) * itemSize.width
            frame.origin.y = CGFloat(rowPosition) * itemSize.height
            frame.size = itemSize
            attr.frame = frame

            return attr
    }
}

这是 @GuilhermeSprint 答案的 Swift 3 版本

代码：

public class HorizontalCollectionViewLayout : UICollectionViewLayout {
    var itemSize = CGSize(width: 0, height: 0) {
        didSet {
            invalidateLayout()
        }
    }
    private var cellCount = 0
    private var boundsSize = CGSize(width: 0, height: 0)

    public override func prepare() {
        cellCount = self.collectionView!.numberOfItems(inSection: 0)
        boundsSize = self.collectionView!.bounds.size
    }
    public override var collectionViewContentSize: CGSize {
        let verticalItemsCount = Int(floor(boundsSize.height / itemSize.height))
        let horizontalItemsCount = Int(floor(boundsSize.width / itemSize.width))

        let itemsPerPage = verticalItemsCount * horizontalItemsCount
        let numberOfItems = cellCount
        let numberOfPages = Int(ceil(Double(numberOfItems) / Double(itemsPerPage)))

        var size = boundsSize
        size.width = CGFloat(numberOfPages) * boundsSize.width
        return size
    }

    public override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        var allAttributes = [UICollectionViewLayoutAttributes]()
        for i in 0...(cellCount-1) {
            let indexPath = IndexPath(row: i, section: 0)
            let attr = self.computeLayoutAttributesForCellAt(indexPath: indexPath)
            allAttributes.append(attr)
        }
        return allAttributes
    }

    public override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        return computeLayoutAttributesForCellAt(indexPath: indexPath)
    }

    public override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true
    }

    private func computeLayoutAttributesForCellAt(indexPath:IndexPath)
        -> UICollectionViewLayoutAttributes {
            let row = indexPath.row
            let bounds = self.collectionView!.bounds

            let verticalItemsCount = Int(floor(boundsSize.height / itemSize.height))
            let horizontalItemsCount = Int(floor(boundsSize.width / itemSize.width))
            let itemsPerPage = verticalItemsCount * horizontalItemsCount

            let columnPosition = row % horizontalItemsCount
            let rowPosition = (row/horizontalItemsCount)%verticalItemsCount
            let itemPage = Int(floor(Double(row)/Double(itemsPerPage)))

            let attr = UICollectionViewLayoutAttributes(forCellWith: indexPath)

            var frame = CGRectMake(0, 0, 0, 0)
            frame.origin.x = CGFloat(itemPage) * bounds.size.width + CGFloat(columnPosition) * itemSize.width
            frame.origin.y = CGFloat(rowPosition) * itemSize.height
            frame.size = itemSize
            attr.frame = frame

            return attr
    }
}

用法：

    // I want to have 4 items in the page / see screenshot below
    let itemWidth = collectionView.frame.width / 2.0
    let itemHeight = collectionView.frame.height / 2.0
    let horizontalCV = HorizontalCollectionViewLayout();
    horizontalCV.itemSize = CGSize(width: itemWidth, height: itemHeight)
    collectionView.collectionViewLayout = horizontalCV

结果

如果你想检查我的代表扩展名

extension MyViewController : UICollectionViewDelegateFlowLayout, UICollectionViewDataSource{
    // Delegate
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        print("Clicked")
    }

    // DataSource
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: BottomMenuCCell.xib, for: indexPath) as? BottomMenuCCell {
            cell.ibi = bottomMenuButtons[indexPath.row]
            cell.layer.borderWidth = 0
            return cell
        }
        return BaseCollectionCell()
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize.init(width: (collectionView.width / 2.0), height: collectionView.height / 2.0)
    }
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return bottomMenuButtons.count
    }

    // removing spacing between items
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0.0
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0.0
    }
}

Answer 6

可以简单地将UICollectionView.xib中的Scroll Direction更改为Horizo​​ntal。并使用数组中元素的正确顺序。

Answer 7

当然，您最后的选择是在外部水平滚动集合视图中的每个部分内使用多个垂直集合视图。 除了增加代码复杂性和执行段间单元格动画的困难之外，我无法想到这种方法的主要问题。

Answer 8

@interface HorizontalCollectionViewLayout : UICollectionViewFlowLayout

@end

@implementation HorizontalCollectionViewLayout

- (instancetype)init
{
    self = [super init];
    if (self) {
        self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
        self.minimumLineSpacing = 0;
        self.minimumInteritemSpacing = 0;
    }
    return self;
}

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *attributesArray = [super layoutAttributesForElementsInRect:rect];

    NSInteger verticalItemsCount = (NSInteger)floorf(self.collectionView.bounds.size.height / self.itemSize.height);
    NSInteger horizontalItemsCount = (NSInteger)floorf(self.collectionView.bounds.size.width / self.itemSize.width);
    NSInteger itemsPerPage = verticalItemsCount * horizontalItemsCount;

    for (NSInteger i = 0; i < attributesArray.count; i++) {
        UICollectionViewLayoutAttributes *attributes = attributesArray[i];
        NSInteger currentPage = (NSInteger)floor((double)i / (double)itemsPerPage);
        NSInteger currentRow = (NSInteger)floor((double)(i - currentPage * itemsPerPage) / (double)horizontalItemsCount);
        NSInteger currentColumn = i % horizontalItemsCount;
        CGRect frame = attributes.frame;
        frame.origin.x = self.itemSize.width * currentColumn + currentPage * self.collectionView.bounds.size.width;
        frame.origin.y = self.itemSize.height * currentRow;
        attributes.frame = frame;
    }
    return attributesArray;
}

- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
    return YES;
}

@end