iOS功能列表

1.弹幕：

https://github.com/zkfpk6/YGFlyCommentManager-Danmaku

2.瀑布流：

- (void)prepareLayout; 准备布局cell

先存储各列MaxY值

再循环执行 - (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath，设置新的cell布局属性并存储

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath；  改变cell布局属性

已知宽度，让代理根据实际内容计算高度返回，至此最新的size可得到，然后遍历MaxY数组，找出最短的是哪一列， 最后根据最短列 计算出X 、Y值，设置UICollectionViewLayoutAttributes的frame属性，并更新MaxY数组。

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect；返回所有的cell布局属性

返回所有cell的布局属性（prepareLayout中存储的）

- (CGSize)collectionViewContentSize；

设置ContentSize

计算出collectionView的contentSize（遍历MaxY数组找出最长列即可得到新的高度）。详细代码如下@interface RealityShowLayout ()/** 这个字典用来存储每一列最大的Y值(每一列的高度) */@property (nonatomic, strong) NSMutableDictionary *maxYDict;/** 存放所有的布局属性 */@property(nonatomic,strong)NSMutableArray *attributeArray;@end@implementation RealityShowLayout- (NSMutableDictionary *)maxYDict {      if (!_maxYDict) {    self.maxYDict = [[NSMutableDictionary alloc] init]; }  return _maxYDict;}- (NSMutableArray *)attributeArray { if (!_attributeArray) {  self.attributeArray = [[NSMutableArray alloc] init];  } return _attributeArray;}#pragma mark -初始化默认值- (instancetype)init { if (self = [super init]) { self.columnMargin = 10;  self.rowMargin = 10;  self.columnsCount = 2;  self.sectionInset = UIEdgeInsetsMake(0, 10, 10, 10); }  return self;}- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds { return YES;}- (void)prepareLayout { [super prepareLayout];  // 1.清空最大的Y值  for (int i = 0; i<2; i++) { NSString *column = [NSString stringWithFormat:@"%d", I]; self.maxYDict[column] = @(self.sectionInset.top);  } [self.attributeArray removeAllObjects]; // 总 item 数 NSInteger count = [self.collectionView numberOfItemsInSection:0];  for (int i = 0; i *)layoutAttributesForElementsInRect:(CGRect)rect {    return self.attributeArray;}// 计算ContentSize- (CGSize)collectionViewContentSize {    // 默认最大Y值在第0列    __block NSString *maxColumn = @"0";    [self.maxYDict enumerateKeysAndObjectsUsingBlock:^(NSString *column, NSNumber *maxY, BOOL *stop) {        if ([maxY floatValue] > [self.maxYDict[maxColumn] floatValue]) {            maxColumn = column;        }    }];    return CGSizeMake(0, [self.maxYDict[maxColumn] floatValue] + self.sectionInset.bottom);}- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {    // 1.计算尺寸    CGFloat width = (self.collectionView.frame.size.width - self.sectionInset.left - self.sectionInset.right - (self.columnsCount - 1) * self.columnMargin) / self.columnsCount;    // 代理计算传入高的值    CGFloat height = [self.delegate flowLayout:self heightForWidth:width atIndexPath:indexPath];    // 2.0假设最短的那一列的第0列    __block NSString *minColumn = @"0";    // 遍历字典找出最短的那一列    [self.maxYDict enumerateKeysAndObjectsUsingBlock:^(NSString *column, NSNumber *maxY, BOOL *stop) {        if ([maxY floatValue] < [self.maxYDict[minColumn] floatValue]) {                minColumn = column;        }    }];    // 2.1计算位置        CGFloat x = self.sectionInset.left + (self.columnMargin + width) * [minColumn intValue];        CGFloat y = [self.maxYDict[minColumn] floatValue]+ _rowMargin;        self.maxYDict[minColumn] = @(y + height);        // 3.创建属性        UICollectionViewLayoutAttributes *attrs = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];        attrs.frame = CGRectMake(x, y, width, height);      return attrs;}横向瀑布流原理一样........此处省略一万字

3.进度条

https://github.com/AliThink/HorizontalProgress