UICollectionView 自定义行分隔符

Question

我想在UICollectionView 中为我们的新应用制作2pt 黑色分隔符。我们的应用程序的屏幕截图如下。我们不能使用UITableView，因为我们有自定义插入/删除动画、滚动和视差效果等等。

Answer 1

我从三个想法开始：

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

前两个变体被拒绝，因为意识形态不一致、自定义动画和内容低于集合。我也已经有了自定义布局。

我将使用UICollectionViewFlowLayout 的自定义子类来描述这些步骤。

--1--

实现自定义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。还要在单元格之间设置行距。

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

--3--

在自定义UICollectionViewFlowLayout 子类中，我们应该返回UICollectionViewLayoutAttributes 以获取来自layoutAttributesForElementsInRect 的装饰。

- (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--

对于可见的矩形，我们应该返回可见的装饰索引路径。

- (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--

我们还应该实现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--

有时我发现此解决方案会在装饰外观上出现视觉故障，通过实施 initialLayoutAttributesForAppearingDecorationElementOfKind 已解决此问题。

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

就是这样。代码不多，但做得对。

Answer 2

Swift 中的快速解决方案

1.创建 CustomFlowLayout.swift 文件并粘贴下一段代码

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
    }
}

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

3.更改分隔符颜色

在 SeparatorView 中，您可以更改 init 中分隔符的颜色

4.更改分隔符的高度

你可以用两种不同的方式来做

• 在故事板中。更改属性Min Spacing for Lines

或

• 在代码中。为minimumLineSpacing 设置值

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

Answer 3

Anton 的建议很好，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了单元格的布局属性，包括它们的 frame 和 indexPath，所以您有足够的信息来计算分隔符的框架，只需覆盖此方法并内省单元格布局属性：

- (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 4

谢谢，Anton 和 Werner，他们都帮助了我 - 我已经在您的帮助下制作了拖放解决方案，作为 UICollectionView 上的一个类别，我想我会分享结果：

UICollectionView+Separators.h

#import <UIKit/UIKit.h>

@interface UICollectionView (Separators)

@property (nonatomic) BOOL sep_useCellSeparators;
@property (nonatomic, strong) UIColor *sep_separatorColor;

@end

UICollectionView+Separators.m

#import "UICollectionView+Separators.h"
@import ObjectiveC;

#pragma mark -
#pragma mark -

@interface UICollectionViewLayoutAttributes (SEPLayoutAttributes)

@property (nonatomic, strong) UIColor *sep_separatorColor;

@end

@implementation UICollectionViewLayoutAttributes (SEPLayoutAttributes)

- (void)setSep_separatorColor:(UIColor *)sep_separatorColor
{
    objc_setAssociatedObject(self, @selector(sep_separatorColor), sep_separatorColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIColor *)sep_separatorColor
{
    return objc_getAssociatedObject(self, @selector(sep_separatorColor));
}

@end

#pragma mark -
#pragma mark -

@interface SEPCollectionViewCellSeparatorView : UICollectionReusableView

@end

@implementation SEPCollectionViewCellSeparatorView

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

    return self;
}

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

    if (layoutAttributes.sep_separatorColor != nil)
    {
        self.backgroundColor = layoutAttributes.sep_separatorColor;
    }
}

@end

#pragma mark -
#pragma mark -

static NSString *const kCollectionViewCellSeparatorReuseId = @"kCollectionViewCellSeparatorReuseId";

@implementation UICollectionViewFlowLayout (SEPCellSeparators)

#pragma mark - Setters/getters

- (void)setSep_separatorColor:(UIColor *)sep_separatorColor
{
    objc_setAssociatedObject(self, @selector(sep_separatorColor), sep_separatorColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

    [self invalidateLayout];
}

- (UIColor *)sep_separatorColor
{
    return objc_getAssociatedObject(self, @selector(sep_separatorColor));
}

- (void)setSep_useCellSeparators:(BOOL)sep_useCellSeparators
{
    if (self.sep_useCellSeparators != sep_useCellSeparators)
    {
        objc_setAssociatedObject(self, @selector(sep_useCellSeparators), @(sep_useCellSeparators), OBJC_ASSOCIATION_RETAIN_NONATOMIC);

        [self registerClass:[SEPCollectionViewCellSeparatorView class] forDecorationViewOfKind:kCollectionViewCellSeparatorReuseId];
        [self invalidateLayout];
    }
}

- (BOOL)sep_useCellSeparators
{
    return [objc_getAssociatedObject(self, @selector(sep_useCellSeparators)) boolValue];
}

#pragma mark - Method Swizzling

+ (void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];

        SEL originalSelector = @selector(layoutAttributesForElementsInRect:);
        SEL swizzledSelector = @selector(swizzle_layoutAttributesForElementsInRect:);

        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

        BOOL didAddMethod =
        class_addMethod(class,
                        originalSelector,
                        method_getImplementation(swizzledMethod),
                        method_getTypeEncoding(swizzledMethod));

        if (didAddMethod) {
            class_replaceMethod(class,
                                swizzledSelector,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

- (NSArray<UICollectionViewLayoutAttributes *> *)swizzle_layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *layoutAttributesArray = [self swizzle_layoutAttributesForElementsInRect:rect];

    if (self.sep_useCellSeparators == NO)
    {
        return layoutAttributesArray;
    }

    CGFloat lineSpacing = self.minimumLineSpacing;

    NSMutableArray *decorationAttributes = [[NSMutableArray alloc] initWithCapacity:layoutAttributesArray.count];

    for (UICollectionViewLayoutAttributes *layoutAttributes in layoutAttributesArray)
    {
        NSIndexPath *indexPath = layoutAttributes.indexPath;

        if (indexPath.item > 0)
        {
            id <UICollectionViewDelegateFlowLayout> delegate = (id <UICollectionViewDelegateFlowLayout>)self.collectionView.delegate;
            if ([delegate respondsToSelector:@selector(collectionView:layout:minimumLineSpacingForSectionAtIndex:)])
            {
                lineSpacing = [delegate collectionView:self.collectionView layout:self minimumLineSpacingForSectionAtIndex:indexPath.section];
            }

            UICollectionViewLayoutAttributes *separatorAttributes = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:kCollectionViewCellSeparatorReuseId withIndexPath:indexPath];
            CGRect cellFrame = layoutAttributes.frame;

            if (self.scrollDirection == UICollectionViewScrollDirectionHorizontal)
            {
                separatorAttributes.frame = CGRectMake(cellFrame.origin.x - lineSpacing, cellFrame.origin.y, lineSpacing, cellFrame.size.height);
            }
            else
            {
                separatorAttributes.frame = CGRectMake(cellFrame.origin.x, cellFrame.origin.y - lineSpacing, cellFrame.size.width, lineSpacing);
            }

            separatorAttributes.zIndex = 1000;

            separatorAttributes.sep_separatorColor = self.sep_separatorColor;

            [decorationAttributes addObject:separatorAttributes];
        }
    }

    return [layoutAttributesArray arrayByAddingObjectsFromArray:decorationAttributes];
}

@end

#pragma mark -
#pragma mark -

@implementation UICollectionView (Separators)

- (UICollectionViewFlowLayout *)sep_flowLayout
{
    if ([self.collectionViewLayout isKindOfClass:[UICollectionViewFlowLayout class]])
    {
        return (UICollectionViewFlowLayout *)self.collectionViewLayout;
    }
    return nil;
}

- (void)setSep_separatorColor:(UIColor *)sep_separatorColor
{
    [self.sep_flowLayout setSep_separatorColor:sep_separatorColor];
}

- (UIColor *)sep_separatorColor
{
    return [self.sep_flowLayout sep_separatorColor];
}

- (void)setSep_useCellSeparators:(BOOL)sep_useCellSeparators
{
    [self.sep_flowLayout setSep_useCellSeparators:sep_useCellSeparators];
}

- (BOOL)sep_useCellSeparators
{
    return [self.sep_flowLayout sep_useCellSeparators];
}

@end

使用 Objective-C 运行时和一些 swizzling，单元格分隔符可以通过几行添加到任何现有的 UICollectionView，其布局是/继承自 UICollectionViewFlowLayout。

示例用法：

#import "UICollectionView+Separators.h"
...
self.collectionView.sep_useCellSeparators = YES;
self.collectionView.sep_separatorColor = [UIColor blackColor];

几个注意事项：

• 可以使用collectionView:layout:minimumLineSpacingForSectionAtIndex: 确定每个部分的分隔符高度/宽度，如果未实现则回退到minimumLineSpacing
• 专为处理水平或垂直滚动​​方向而设计

希望对你有帮助

Answer 5

这是来自 Anton Gaenko 的版本，但使用 C# 实现，这可能对 Xamarin 用户有用：

[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 6

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)
}

需要改成：

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

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