Question

我想在UICollectionView为我们的新应用制作 2pt黑色分隔符。我们的应用程序截图如下。我们无法使用UITableView，因为我们有自定义插入/删除动画，滚动和视差效果等。

Example

Answer 1

我从三个想法开始如何制作它：

在单元格
使用纯黑色背景和minimumLineSpacing，因此我们会在单元格之间的空格中看到背景
使用自定义布局并将此分隔符实现为装饰

前两个变种被拒绝，因为意识形态不一致，自定义动画和收集下面的内容。我也已经有了自定义布局。

我将使用UICollectionViewFlowLayout的自定义子类描述步骤。

- 1 -

实施自定义UICollectionReusableView子类。

@interface FLCollectionSeparator : UICollectionReusableView

@end

@implementation FLCollectionSeparator

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor blackColor];
    }

    return self;
}

- (void)applyLayoutAttributes:(UICollectionViewLayoutAttributes *)layoutAttributes {
    self.frame = layoutAttributes.frame;
}

@end

- 2 -

说布局使用自定义装饰。还要在单元格之间建立行间距。

UICollectionViewFlowLayout* layout = (UICollectionViewFlowLayout*) self.newsCollection.collectionViewLayout;
[layout registerClass:[FLCollectionSeparator class] forDecorationViewOfKind:@"Separator"];
layout.minimumLineSpacing = 2;

- 3 -

在自定义UICollectionViewFlowLayout子类中，我们应该从UICollectionViewLayoutAttributes返回layoutAttributesForElementsInRect来装饰。

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
    ... collect here layout attributes for cells ... 

    NSMutableArray *decorationAttributes = [NSMutableArray array];
    NSArray *visibleIndexPaths = [self indexPathsOfSeparatorsInRect:rect]; // will implement below

    for (NSIndexPath *indexPath in visibleIndexPaths) {
        UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForDecorationViewOfKind:@"Separator" atIndexPath:indexPath];
        [decorationAttributes addObject:attributes];
    }

    return [layoutAttributesArray arrayByAddingObjectsFromArray:decorationAttributes];
}

- 4 -

对于可见的rect，我们应该返回可见的装饰索引。

- (NSArray*)indexPathsOfSeparatorsInRect:(CGRect)rect {
    NSInteger firstCellIndexToShow = floorf(rect.origin.y / self.itemSize.height);
    NSInteger lastCellIndexToShow = floorf((rect.origin.y + CGRectGetHeight(rect)) / self.itemSize.height);
    NSInteger countOfItems = [self.collectionView.dataSource collectionView:self.collectionView numberOfItemsInSection:0];

    NSMutableArray* indexPaths = [NSMutableArray new];
    for (int i = MAX(firstCellIndexToShow, 0); i <= lastCellIndexToShow; i++) {
        if (i < countOfItems) {
            [indexPaths addObject:[NSIndexPath indexPathForRow:i inSection:0]];
        }
    }
    return indexPaths;
}

- 5 -

我们也应该实施layoutAttributesForDecorationViewOfKind。

- (UICollectionViewLayoutAttributes *)layoutAttributesForDecorationViewOfKind:(NSString *)decorationViewKind atIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewLayoutAttributes *layoutAttributes = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:decorationViewKind withIndexPath:indexPath];
    CGFloat decorationOffset = (indexPath.row + 1) * self.itemSize.height + indexPath.row * self.minimumLineSpacing;
    layoutAttributes.frame = CGRectMake(0.0, decorationOffset, self.collectionViewContentSize.width, self.minimumLineSpacing);
    layoutAttributes.zIndex = 1000;

    return layoutAttributes;
}

- 6 -

有时我发现这个解决方案会给出带有装饰外观的视觉故障，并通过实施initialLayoutAttributesForAppearingDecorationElementOfKind来解决。

- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingDecorationElementOfKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)decorationIndexPath {
    UICollectionViewLayoutAttributes *layoutAttributes =  [self layoutAttributesForDecorationViewOfKind:elementKind atIndexPath:decorationIndexPath];
    return layoutAttributes;
}

这就是全部。没有太多的代码，但做得很好。

Answer 2

Anton的优秀建议，但我认为FlowLayout子类中的实现可以更简单。因为 - （NSArray *）layoutAttributesForElementsInRect：（CGRect）rect的超级实现已经返回包括它们的frame和indexPath的单元格的布局属性，所以你有足够的信息来通过仅覆盖此方法并内省单元格布局来计算分隔符的帧。属性：

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

    CGFloat lineWidth = self.minimumLineSpacing;
    NSMutableArray *decorationAttributes = [[NSMutableArray alloc] initWithCapacity:layoutAttributesArray.count];

    for (UICollectionViewLayoutAttributes *layoutAttributes in layoutAttributesArray) {
        //Add separator for every row except the first
        NSIndexPath *indexPath = layoutAttributes.indexPath;
        if (indexPath.item > 0) {
            UICollectionViewLayoutAttributes *separatorAttributes = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:kCellSeparatorKind withIndexPath:indexPath];
            CGRect cellFrame = layoutAttributes.frame;

            //In my case I have a horizontal grid, where I need vertical separators, but the separator frame can be calculated as needed
            //e.g. top, or both top and left
            separatorAttributes.frame = CGRectMake(cellFrame.origin.x - lineWidth, cellFrame.origin.y, lineWidth, cellFrame.size.height);
            separatorAttributes.zIndex = 1000;
            [decorationAttributes addObject:separatorAttributes];
        }
    }
    return [layoutAttributesArray arrayByAddingObjectsFromArray:decorationAttributes];
}

Answer 3

Swift中的快速解决方案

<强> 1。创建CustomFlowLayout.swift文件并粘贴下一个代码

import UIKit

private let separatorDecorationView = "separator"

final class CustomFlowLayout: UICollectionViewFlowLayout {

    override func awakeFromNib() {
        super.awakeFromNib()
        register(SeparatorView.self, forDecorationViewOfKind: separatorDecorationView)
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        let layoutAttributes = super.layoutAttributesForElements(in: rect) ?? []
        let lineWidth = self.minimumLineSpacing

        var decorationAttributes: [UICollectionViewLayoutAttributes] = []

        // skip first cell
        for layoutAttribute in layoutAttributes where layoutAttribute.indexPath.item > 0 {
            let separatorAttribute = UICollectionViewLayoutAttributes(forDecorationViewOfKind: separatorDecorationView,
                                                                      with: layoutAttribute.indexPath)
            let cellFrame = layoutAttribute.frame
            separatorAttribute.frame = CGRect(x: cellFrame.origin.x,
                                              y: cellFrame.origin.y - lineWidth,
                                              width: cellFrame.size.width,
                                              height: lineWidth)
            separatorAttribute.zIndex = Int.max
            decorationAttributes.append(separatorAttribute)
        }

        return layoutAttributes + decorationAttributes
    }

}

private final class SeparatorView: UICollectionReusableView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.backgroundColor = .red
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func apply(_ layoutAttributes: UICollectionViewLayoutAttributes) {
        self.frame = layoutAttributes.frame
    }
}

<强> 2。设置自定义流程

在界面构建器中选择您的UICollectionViewFlow并设置我们的新类名CustomFlowLayout

第3。更改分隔符颜色

在SeparatorView中，您可以更改init

中分隔符的颜色

<强> 4。更改分隔符的高度

你可以用两种不同的方式做到这一点

在故事中。更改属性Min Spacing for Lines

OR

在代码中。设置minimumLineSpacing

的值

override func awakeFromNib() {
    super.awakeFromNib()
    register(SeparatorView.self, forDecorationViewOfKind: separatorDecorationView)
    minimumLineSpacing = 2 }

Answer 4

以下是Anton Gaenko的版本，但是在C＃中实现，这对Xamarin用户来说非常有用：

[Register(nameof(FLCollectionSeparator))]
public class FLCollectionSeparator : UICollectionReusableView
{
    public FLCollectionSeparator(CGRect frame) : base(frame)
    {
        this.BackgroundColor = UIColor.Black;
    }
    public FLCollectionSeparator(IntPtr handle) : base(handle)
    {
        this.BackgroundColor = UIColor.Black;
    }
    public override void ApplyLayoutAttributes(UICollectionViewLayoutAttributes layoutAttributes)
    {
        this.Frame = layoutAttributes.Frame;
    }
}

[Register(nameof(UILinedSpacedViewFlowLayout))]
public class UILinedSpacedViewFlowLayout : UICollectionViewFlowLayout
{
    public const string SeparatorAttribute = "Separator";
    private static readonly NSString NSSeparatorAttribute = new NSString(SeparatorAttribute);
    public UILinedSpacedViewFlowLayout() : base() { this.InternalInit(); }
    public UILinedSpacedViewFlowLayout(NSCoder coder) : base (coder) { this.InternalInit(); }
    protected UILinedSpacedViewFlowLayout(NSObjectFlag t) : base(t) { this.InternalInit(); }
    private void InternalInit()
    {
        this.RegisterClassForDecorationView(typeof(FLCollectionSeparator), NSSeparatorAttribute);
    }
    public override UICollectionViewLayoutAttributes[] LayoutAttributesForElementsInRect(CGRect rect)
    {
        return LayoutAttributesForElementsInRect_internal(rect).ToArray();
    }
    private IEnumerable<UICollectionViewLayoutAttributes> LayoutAttributesForElementsInRect_internal(CGRect rect)
    {
        foreach (var baseDecorationAttr in base.LayoutAttributesForElementsInRect(rect))
        {
            yield return baseDecorationAttr;
        }
        foreach (var indexPath in this.IndexPathsOfSeparatorsInRect(rect))
        {
            yield return this.LayoutAttributesForDecorationView(NSSeparatorAttribute, indexPath);
        }
    }
    private IEnumerable<NSIndexPath> IndexPathsOfSeparatorsInRect(CGRect rect)
    {
        int firstCellIndexToShow = (int)(rect.Y / this.ItemSize.Height);
        int lastCellIndexToShow  = (int)((rect.Y + rect.Height) / this.ItemSize.Height);
        int countOfItems = (int)this.CollectionView.DataSource.GetItemsCount(this.CollectionView, 0);
        for (int i = Math.Max(firstCellIndexToShow, 0); i <= lastCellIndexToShow; i++)
        {
            if (i < countOfItems)
            {
                yield return NSIndexPath.FromItemSection(i, 0);
            }
        }
    }
    public override UICollectionViewLayoutAttributes LayoutAttributesForDecorationView(NSString kind, NSIndexPath indexPath)
    {
        UICollectionViewLayoutAttributes layoutAttributes = base.LayoutAttributesForDecorationView(kind, indexPath);
        var decorationOffset = (indexPath.Row + 1) * this.ItemSize.Height + indexPath.Row * this.MinimumLineSpacing + this.HeaderReferenceSize.Height;
        layoutAttributes = UICollectionViewLayoutAttributes.CreateForDecorationView(kind, indexPath);
        layoutAttributes.Frame = new CGRect(0, decorationOffset, this.CollectionViewContentSize.Width, this.MinimumLineSpacing);
        layoutAttributes.ZIndex = 1000;
        return layoutAttributes;
    }
    public override UICollectionViewLayoutAttributes InitialLayoutAttributesForAppearingDecorationElement(NSString elementKind, NSIndexPath decorationIndexPath)
    {
        return base.InitialLayoutAttributesForAppearingDecorationElement(elementKind, decorationIndexPath);
    }
}

Answer 5

在@SlavikVoloshyn答案中，以编程方式使用此部分：

override func awakeFromNib() {
    super.awakeFromNib()
    register(SeparatorView.self, forDecorationViewOfKind: separatorDecorationView)
}

需要更改为：

override init() {
    super.init()
    register(SeparatorView.self, forDecorationViewOfKind: separatorDecorationView)
    minimumLineSpacing = 2
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

UICollectionView自定义行分隔符

5 个答案: