iOS UICollectionView

利用UICollectionView实现如下效果:

Screen Shot 2015-08-01 at 08.33.15.png

• 自定义BIDContentCell继承自UICollectionViewCell:

#import <UIKit/UIKit.h>

@interface BIDContentCell : UICollectionViewCell

@property (strong, nonatomic) UILabel *label;
@property (copy, nonatomic) NSString *text;

+ (CGSize)sizeForContentString: (NSString *)string;

@end 

#import "BIDContentCell.h"

@implementation BIDContentCell

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    
    if (self) {
        self.label = [[UILabel alloc] initWithFrame:self.contentView.bounds];
        self.label.opaque = NO;
        
        self.label.backgroundColor = [UIColor colorWithRed:0.8 green:0.9 blue:1.0 alpha:1.0];
        
        self.label.textColor = [UIColor blackColor];
        
        self.label.textAlignment = NSTextAlignmentCenter;
        self.label.font = [[self class] defaultFont];
        [self.contentView addSubview:self.label];
    }
    
    return self;
}

+ (UIFont *)defaultFont {
    return [UIFont preferredFontForTextStyle:UIFontTextStyleBody];
}

+ (CGSize)sizeForContentString:(NSString *)string {
    CGSize maxSize = CGSizeMake(300, 100);
    NSStringDrawingOptions opts = NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading;
    NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
    [style setLineBreakMode:NSLineBreakByCharWrapping];
    
    NSDictionary *attributes = @{
                                 NSFontAttributeName : [self defaultFont],
                                 NSParagraphStyleAttributeName : style
                                 };
    CGRect rect = [string boundingRectWithSize:maxSize options:opts attributes:attributes context:nil];
    return rect.size;
}

- (NSString *)text {
    return self.label.text;
}

- (void)setText:(NSString *)text {
    self.label.text = text;
    CGRect newLabelFrame = self.label.frame;
    CGRect newContentFrame = self.contentView.frame;
    CGSize textSize = [[self class] sizeForContentString:text];
    newLabelFrame.size = textSize;
    self.label.frame = newLabelFrame;
    self.contentView.frame = newContentFrame;
}

@end  

+ (CGSize)sizeForContentString: (NSString *)string;这个方法返回每个word所占的Size

• BIDHeaderCell继承自BIDContentCell

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.label.backgroundColor = [UIColor colorWithRed:0.9 green:0.9 blue:0.8 alpha:1.0];
        self.label.textColor = [UIColor blackColor];
    }
    
    return self;
}

+ (UIFont *)defaultFont {
    return [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];
} 

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.section = @[
                     @{
                         @"header" : @"First Witch",
                         @"content" : @"Hey, when will the three of us meet up later?"
                         },
                     @{
                         @"header" : @"Second Witch",
                         @"content" : @"When everything's straightened out."
                         },
                     @{
                         @"header" : @"Third Witch",
                         @"content" : @"That'll be just before sunset."
                         },
                     @{ @"header" : @"First Witch",
                         @"content" : @"Where?" },
                     @{ @"header" : @"Second Witch",
                        @"content" : @"The dirt patch." },
                     @{ @"header" : @"Third Witch",
                        @"content" : @"I guess we'll see Mac there." }
                     ];
    [self.collectionView registerClass:[BIDContentCell class] forCellWithReuseIdentifier:@"CONTENT"];
    self.collectionView.backgroundColor = [UIColor whiteColor];
    
    UIEdgeInsets contentInset = self.collectionView.contentInset;
    contentInset.top = 20;
    [self.collectionView setContentInset:contentInset];
    
    UICollectionViewLayout *layout = self.collectionView.collectionViewLayout;
    UICollectionViewFlowLayout *flow = (UICollectionViewFlowLayout *)layout;
    flow.sectionInset = UIEdgeInsetsMake(10, 20, 30, 40);
    
    [self.collectionView registerClass:[BIDHeaderCell class]
            forSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                   withReuseIdentifier:@"HEADER"];
    
    flow.headerReferenceSize = CGSizeMake(100, 25);
}

- (NSArray *)wordsInSetction:(NSInteger)section {
    NSString *content = self.section[section][@"content"];
    NSCharacterSet *space = [NSCharacterSet whitespaceAndNewlineCharacterSet];
    NSArray *words = [content componentsSeparatedByCharactersInSet:space];
    
    return words;
}

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return [self.section count];
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    NSArray *words = [self wordsInSetction:section];
    return [words count];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    NSArray *words = [self wordsInSetction:indexPath.section];
    BIDContentCell *cell = [self.collectionView dequeueReusableCellWithReuseIdentifier:@"CONTENT"forIndexPath:indexPath];
    
    cell.text = words[indexPath.row];
    return cell;
}

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout*)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    NSArray *words = [self wordsInSetction:indexPath.section];
    CGSize size = [BIDContentCell sizeForContentString:words[indexPath.row]];
    return size;
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
           viewForSupplementaryElementOfKind:(NSString *)kind
                                 atIndexPath:(NSIndexPath *)indexPath {
    if ([kind isEqual:UICollectionElementKindSectionHeader]) {
        BIDHeaderCell *cell = [self.collectionView
                               dequeueReusableSupplementaryViewOfKind:kind
                               withReuseIdentifier:@"HEADER"
                               forIndexPath:indexPath];
        
        cell.text = self.section[indexPath.section][@"header"];
        return cell;
    }
    return nil;
}