《精通 iOS 开发》第 10 章学习笔记

自定义单元

1.创建标签：

- (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;
}

2.重写text属性：

- (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;
  newContentFrame.size = textSize;
  self.label.frame = newLabelFrame;
  self.contentView.frame = newContentFrame;
}

3.获取字体尺寸：

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

+ (CGSize)sizeForContentString:(NSString *)string {
  CGSize maxSize = CGSizeMake(300, 1000);

  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;
}

配置视图控制器

1.初始化：

- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
  self.sections = @[
    @{
      @"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, 20);

  [self.collectionView registerClass:[BIDHeaderCell class]
          forSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                 withReuseIdentifier:@"HEADER"];

  flow.headerReferenceSize = CGSizeMake(100, 25);
}

2.实现流式布局：

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

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

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

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  NSArray *words = [self wordsInSection: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 wordsInSection: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.sections[indexPath.row][@"header"];
    return cell;
  }
  return nil;
}