用于UICollectionView的SectionIndexTitles [英] SectionIndexTitles for a UICollectionView

问题描述

所以我使用搜索功能和 sectionIndexTitles 实现了一个正确的 TableView 。现在，我正在尝试实现一个 UICollectionView ，它到目前为止工作，除了我不能轻易拥有 sectionIndexTitles （右侧滚动条）。

So I implemented a proper TableView with a search functionality and sectionIndexTitles. Now, I am trying to implement a UICollectionView and it is working so far, except that I can't easily have sectionIndexTitles (the right scroll bar).

如果我查看Facebook应用程序，它看起来像 UICollectionView ，但确实 sectionIndexTitles 和一个搜索栏。我似乎无法为 UICollectionView 模型找到这样的函数。

If I look at the Facebook Application, it looks like a UICollectionView, but with indeed sectionIndexTitles and a searchbar. I can't seem to find such functions for the UICollectionView model.

任何想法？！

谢谢！

推荐答案

我有类似的要求（对于水平集合视图）并最终建立了一个索引视图子类我自己。

I had a similar requirement (for a horizontal collection view) and ended up building an index view subclass myself.

我打算开源它，但这可能要等到下个月，所以这里有一个存根来启动你：

I plan to open-source it but that will likely have to wait until next month, so here's a stub to get you started:

YMCollectionIndexView.h

@interface YMCollectionIndexView : UIControl

- (id) initWithFrame:(CGRect)frame indexTitles:(NSArray *)indexTitles;

// Model
@property (strong, nonatomic) NSArray *indexTitles; // NSString
@property (readonly, nonatomic) NSUInteger currentIndex;
- (NSString *)currentIndexTitle;

@end

YMCollectionIndexView.m

#import "YMCollectionIndexView.h"

@interface YMCollectionIndexView ()
@property (readwrite, nonatomic) NSUInteger currentIndex;
@property (strong, nonatomic) NSArray *indexLabels;
@end

@implementation YMCollectionIndexView

- (id) initWithFrame:(CGRect)frame indexTitles:(NSArray *)indexTitles {
    self = [super initWithFrame:frame];
    if (self) {
        self.indexTitles = indexTitles;
        self.currentIndex = 0;
        // add pan recognizer
    }
    return self;
}

- (void)setIndexTitles:(NSArray *)indexTitles {
    if (_indexTitles == indexTitles) return;
    _indexTitles = indexTitles;
    [self.indexLabels makeObjectsPerformSelector:@selector(removeFromSuperview)];
    [self buildIndexLabels];
}

- (NSString *)currentIndexTitle {
    return self.indexTitles[self.currentIndex];
}

#pragma mark - Subviews

- (void) buildIndexLabels {
    CGFloat cumulativeItemWidth = 0.0; // or height in your (vertical) case
    for (NSString *indexTitle in self.indexTitles) {
            // build and add label
        // add tap recognizer
    }
    self.indexLabels = indexLabels;
}

#pragma mark - Gestures

- (void) handleTap:(UITapGestureRecognizer*)recognizer {
    NSString *indexTitle = ((UILabel *)recognizer.view).text;
    self.currentIndex = [self.indexTitles indexOfObject:indexTitle];
    [self sendActionsForControlEvents:UIControlEventTouchUpInside];
}

// similarly for pan recognizer

@end

在您的视图控制器中：

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.collectionIndexView addTarget:self action:@selector(indexWasTapped:) forControlEvents:UIControlEventTouchUpInside];
    // similarly for pan recognizer
}

- (void)indexWasTapped:(id)sender {
    [self.collectionView scrollToIndexPath:...];
}

// similarly for pan recognizer

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