一. 简述

以可自定义的布局显示的数据项的有序集合。

@interface NSCollectionView : NSView

Merging content and layout to create the final appearance

二. 官方属性方法

// 为收集视图提供数据的对象
@property (nullable, weak) id<NSCollectionViewDataSource> dataSource API_AVAILABLE(macos(10.11)); 
@property (nullable, weak) id<NSCollectionViewPrefetching> prefetchDataSource API_AVAILABLE(macos(10.13));
// 委托对象
@property (nullable, weak) id<NSCollectionViewDelegate> delegate;
// 为收集视图提供数据的数组
@property (copy) NSArray<id> *content;
@property (nullable, strong) NSView *backgroundView API_AVAILABLE(macos(10.11));
// 背景色数组
@property (null_resettable, copy) NSArray<NSColor *> *backgroundColors;
// 背景视图是否随项目及其他内容滚动
@property BOOL backgroundViewScrollsWithContent API_AVAILABLE(macos(10.12));
// 构建集合视图内容的布局对象
@property (nullable, strong) __kindof NSCollectionViewLayout *collectionViewLayout API_AVAILABLE(macos(10.11));

!!! 之后再补充 !!!

三. 示例

1. 效果图

要达到的效果:

• 显示左侧聊天列表
• Split滑动item内控件位置不变动
• 全屏下的显示
• 点击item调整选中色

如下图

效果图

2. 具体代码

2.1 创建NSCollectionView

此处为了方便使用Storyboard创建

创建CollectionView

2.2 配置flowLayout(可以创建或者代理设置)

self.flowLayout = [[NSCollectionViewFlowLayout alloc] init];
self.flowLayout.itemSize = NSMakeSize(self.collectionView.frame.size.width, 60); // item大小
self.flowLayout.minimumLineSpacing = 0; // 最小横向间距
self.flowLayout.minimumInteritemSpacing = 0; // 最小竖向间距
self.collectionView.collectionViewLayout = self.flowLayout;

说明: 这里不使用Storyboard或者代理配置flowLayout的原因是在滑动SplitView的时候要调整itemSize，使用这种方式更方便设置itemSize。

2.3 设置代理

@interface FSMessageVC ()
<
NSSplitViewDelegate,
NSCollectionViewDelegate,
NSCollectionViewDataSource,
NSCollectionViewDelegateFlowLayout
>

self.collectionView.delegate = self;
self.collectionView.dataSource = self;

2.4 设置CollectionView属性

// 设置CollectionView的背景色
self.collectionView.layer.backgroundColor = NSColor.whiteColor.CGColor;
self.collectionView.wantsLayer = YES;
// 设置可选择 ！！！注意！！！不设置为YES会导致点击item无效果
self.collectionView.selectable = YES;

2.5 注册自定义的Item

[self.collectionView registerNib:[[NSNib alloc] initWithNibNamed:@"FSChatCell" bundle:nil]
               forItemWithIdentifier:@"kChatItem"];

2.6 实现代理方法

// 区数
- (NSInteger)numberOfSectionsInCollectionView:(NSCollectionView *)collectionView {
    return 1;
}
// item数量
- (NSInteger)collectionView:(NSCollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return self.dataSource.count;
}
// FSChatCell继承自NSCollectionViewItem
- (nonnull NSCollectionViewItem *)collectionView:(nonnull NSCollectionView *)collectionView itemForRepresentedObjectAtIndexPath:(nonnull NSIndexPath *)indexPath {
    FSChatCell *cell = (FSChatCell *)[collectionView makeItemWithIdentifier:@"kChatItem" forIndexPath:indexPath];
    cell.name = self.dataSource[indexPath.item];
    return cell;
}

- (BOOL)commitEditingAndReturnError:(NSError *__autoreleasing  _Nullable * _Nullable)error {
    return YES;
}

- (void)encodeWithCoder:(nonnull NSCoder *)coder {
    
}

2.7 Split滑动item内控件位置不变动

// 1. 添加NSSplitViewDelegate
self.splitView.delegate = self;

// 最小可滑动的点
- (CGFloat)splitView:(NSSplitView *)splitView constrainMinCoordinate:(CGFloat)proposedMinimumPosition ofSubviewAt:(NSInteger)dividerIndex {
    return 200;
}
// 最大可滑动的点
- (CGFloat)splitView:(NSSplitView *)splitView constrainMaxCoordinate:(CGFloat)proposedMaximumPosition ofSubviewAt:(NSInteger)dividerIndex {
    return 300;
}
// 滑动时的通知代理, 设置itemSize
- (void)splitViewDidResizeSubviews:(NSNotification *)notification {
    self.flowLayout.itemSize = NSMakeSize(self.collectionView.frame.size.width, 60);
}

2.8 全屏下的显示

添加全屏通知在通知的回调方法里调用 self.flowLayout.itemSize = NSMakeSize(self.collectionView.frame.size.width, 60); ，比较简单不再累述。

2.9 点击item调整选中背景色

有两种方式实现：

• didSelectItemsAtIndexPaths和didDeselectItemsAtIndexPaths修改item背景色
• 在自定义item中重写selected方法

// 方式 1
- (void)collectionView:(NSCollectionView *)collectionView didSelectItemsAtIndexPaths:(NSSet<NSIndexPath *> *)indexPaths {
    NSIndexPath *indexPath = indexPaths.allObjects.firstObject;
    FSChatCell *cell = (FSChatCell *)[collectionView itemAtIndexPath:indexPath];
    cell.view.wantsLayer = YES;
    cell.view.layer.backgroundColor = NSColor.lightGrayColor.CGColor;
}

- (void)collectionView:(NSCollectionView *)collectionView didDeselectItemsAtIndexPaths:(NSSet<NSIndexPath *> *)indexPaths {
    NSIndexPath *indexPath = indexPaths.allObjects.firstObject;
    FSChatCell *cell = (FSChatCell *)[collectionView itemAtIndexPath:indexPath];
    cell.view.wantsLayer = YES;
    cell.view.layer.backgroundColor = NSColor.whiteColor.CGColor;
}

// 方式 2 
//  FSChatCell.m
- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.wantsLayer = YES;
      self.view.layer.backgroundColor = NSColor.whiteColor.CGColor;
}

- (void)setSelected:(BOOL)selected {
    super.selected = selected;
    [self changeBgViewColor];
}

- (void)changeBgViewColor {
    if (self.selected) {
        if (self.highlightState == NSCollectionViewItemHighlightForSelection) {
            self.view.layer.backgroundColor = NSColor.lightGrayColor.CGColor;
        } else if (self.highlightState == NSCollectionViewItemHighlightNone ||
                   self.highlightState == NSCollectionViewItemHighlightForDeselection) {
            self.view.layer.backgroundColor = NSColor.whiteColor.CGColor;
        }
    } else {
        self.view.layer.backgroundColor = NSColor.whiteColor.CGColor;
    }
}

2.10 FSChatCell.xib

说明：

• 创建Object对象并绑定FSChatCell

image-20201109174544750

• 连线时最好将控件连在创建的Objects-ChatCell上

image-20201109174737345

2.11 添加头/尾

• 创建FSChatHeaderView

  FSChatHeaderView继承自NSView

• 注册HeaderView

  [self.collectionView registerNib:[[NSNib alloc] initWithNibNamed:@"FSChatHeaderView" bundle:nil]
            forSupplementaryViewOfKind:NSCollectionElementKindSectionHeader
                        withIdentifier:@"kChatHeader"];
  

• 实现代理

- (NSSize)collectionView:(NSCollectionView *)collectionView layout:(NSCollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
    return NSMakeSize(self.collectionView.frame.size.width, 40);
}

- (NSView *)collectionView:(NSCollectionView *)collectionView
viewForSupplementaryElementOfKind:(NSCollectionViewSupplementaryElementKind)kind
               atIndexPath:(NSIndexPath *)indexPath {
    FSChatHeaderView *headerView = [collectionView makeSupplementaryViewOfKind:NSCollectionElementKindSectionHeader
                                                                withIdentifier:@"kChatHeader"
                                                                  forIndexPath:indexPath];
    return headerView;
}

---

Github Demo

说明：

• registerNib/registerClass可以写成宏，代码可以更整洁。

#pragma mark - 注册Nib
#define kRegisterNibCollectionView(collectionView, cell, indetifier)    [collectionView registerNib:[[NSNib alloc] initWithNibNamed:NSStringFromClass([cell class]) bundle:nil] forItemWithIdentifier:indetifier]
#define kRegisterNibTableView(tableView, cell, indetifier)              [tableView registerNib:[[NSNib alloc] initWithNibNamed:NSStringFromClass([cell class]) bundle:nil] forCellReuseIdentifier:indetifier]

• identifier可以写成静态常量

  static NSString *const kChatItemID = @"chatItemID";
  static NSString *const kChatHeaderID = @"chatHeaderID";
  

• MVC/MVP/MVVM模式自己选择，Demo使用MVC完成。

• Demo只设置了头部，尾部同理。

---

个人博客: 🏡 ForgetSou

---