1、首先要写一个继承与NSObject的布局类，记录每一行（列）目前的宽度（高度）。再添加一个新的cell的时候进行判断比较，添加到最短的那一行或一列上。

2、横向的布局类入下，垂直的话就是讲对应的X Y轴数据进行调整即可。WaterfallFlowLayout为布局类，继承与NSObject。.h文件入下

#import // 类的前置声明@class WaterfallFlowLayout;@protocol WaterfallFlowLayoutDelegate // 动态获取 item 宽度- (CGFloat) WaterfallFlowLayout:(WaterfallFlowLayout *) layout widthForItemAtIndexPath:(NSIndexPath *) indexPath;@end@interface WaterfallFlowLayout : UICollectionViewLayout@property (nonatomic,assign) id delegate;@property (nonatomic) NSInteger numberOfColumns;@property (nonatomic) CGFloat minimumLineSpacing;@property (nonatomic) CGFloat minimumInteritemSpacing;@property (nonatomic) UIEdgeInsets sectionInset;@end

WaterfallFlowLayout为布局类，继承与NSObject。.m文件入下

#import "WaterfallFlowLayout.h"@interface WaterfallFlowLayout (){  // 用于记录每一列布局到的宽度  NSMutableArray * _widthOfColumns;  // 用于保存所有item的属性 (frame)  NSMutableArray * _itemsAttributes;}@end@implementation WaterfallFlowLayout- (void) setNumberOfColumns:(NSInteger)numberOfColumns {  if (_numberOfColumns != numberOfColumns) {    _numberOfColumns = numberOfColumns;    // 让原有布局失效，需要重新布局    [self invalidateLayout];  }}- (void)setMinimumLineSpacing:(CGFloat)minimumLineSpacing {  if (_minimumLineSpacing != minimumLineSpacing) {    _minimumLineSpacing = minimumLineSpacing;    [self invalidateLayout];  }}- (void)setMinimumInteritemSpacing:(CGFloat)minimumInteritemSpacing {  if (_minimumInteritemSpacing != minimumInteritemSpacing) {    _minimumInteritemSpacing = minimumInteritemSpacing;    [self invalidateLayout];  }}- (void)setSectionInset:(UIEdgeInsets)sectionInset {  if (!UIEdgeInsetsEqualToEdgeInsets(_sectionInset, sectionInset)) {    _sectionInset = sectionInset;    [self invalidateLayout];  }}//重写方法 1: 准备布局-(void)prepareLayout {  [super prepareLayout];  // 真正的布局在这里完成  if (_itemsAttributes) {    [_itemsAttributes removeAllObjects];  }else {    _itemsAttributes = [[NSMutableArray alloc] init];  }  if (_widthOfColumns) {    [_widthOfColumns removeAllObjects];  }else {    _widthOfColumns = [[NSMutableArray alloc] init];  }  for (NSInteger i = 0; i < self.numberOfColumns; i++) {    // 初始化每一列的宽度(默认为上边距)//    _heightOfColumns[i] = @(self.sectionInset.top);    [_widthOfColumns addObject:@(self.sectionInset.left)];  }  // item的总数  NSInteger count = [self.collectionView numberOfItemsInSection:0];//  CGFloat itemWidth = (self.collectionView.frame.size.width - self.sectionInset.left - self.sectionInset.right - (_numberOfColumns-1) * _minimumInteritemSpacing )/_numberOfColumns;  // 总的高度 (集合视图的宽度)  CGFloat totalHeight = self.collectionView.frame.size.height;  // 有效的高度 (出去间隔及边界)  CGFloat validHeight = totalHeight - self.sectionInset.top - self.self.sectionInset.bottom - (self.numberOfColumns-1) * self.minimumInteritemSpacing;  // 每一个item的高度  CGFloat itemHeight = validHeight/self.numberOfColumns;  // 设置item的默认宽度  CGFloat itemWidth = itemHeight;  for (NSInteger i = 0; i *)layoutAttributesForElementsInRect:(CGRect)rect {  NSMutableArray * array = [NSMutableArray array];  for (UICollectionViewLayoutAttributes * attr in _itemsAttributes) {    // 判断两个矩形是否有交集    if (CGRectIntersectsRect(attr.frame, rect)) {      [array addObject:attr];    }  }  return array;}//重写方法 3: 返回内容的尺寸-(CGSize)collectionViewContentSize {  CGFloat height = self.collectionView.frame.size.height;  NSInteger index = [self indexOfLongestColumn];  CGFloat width = [_widthOfColumns[index] floatValue] + self.sectionInset.right - self.minimumLineSpacing;  return CGSizeMake(width, height);}- (NSInteger) indexOfLongestColumn {  NSInteger index = 0;  for (NSInteger i = 0; i<_numberOfColumns; i++) {    if ([_widthOfColumns[i] floatValue] > [_widthOfColumns[index] floatValue]) {      index = i;    }  }  return index;}- (NSInteger) indexOfShortestColumn {  NSInteger index = 0;  for (NSInteger i = 0; i<_numberOfColumns; i++) {    if ([_widthOfColumns[i] floatValue] < [_widthOfColumns[index] floatValue]) {      index = i;    }  }  return index;}@end

3、上边的这个布局类可以直接复制粘贴下来。然后就是创建你的UICollectionView

在collectionView的cell中可以直接创建imageView或者是label添加到cell上，用来显示数据。 collectionView默认section缩进左右是0 调节横向cell间距 layout.minimumLineSpacing = 10; 调节纵向cell间距 layout.minimumInteritemSpacing = 20; 调节瀑布流显示的行数，当然了你的collectionView的高（宽）足够显示几行（列）就会自动显示多上行（列）； layout.numberOfColumns = 3;

#import "RootViewController.h"#import "WaterfallFlowLayout.h"@interface RootViewController () {  UICollectionView * _collectionView;}@end@implementation RootViewController- (void)dealloc {  [_collectionView release];  [super dealloc];}- (void)viewDidLoad {  [super viewDidLoad];  // 创建集合视图  [self createCollectionView];}- (UICollectionViewLayout *)createLayout {#if 1  WaterfallFlowLayout * layout = [[WaterfallFlowLayout alloc] init];  layout.sectionInset = UIEdgeInsetsMake(20, 20, 20, 20);  layout.minimumLineSpacing = 10;  layout.minimumInteritemSpacing = 20;  layout.numberOfColumns = 3;  layout.delegate = self;  [self performSelector:@selector(changeLayout:) withObject:layout afterDelay:3];#else  UICollectionViewFlowLayout * layout = [[UICollectionViewFlowLayout alloc] init];  layout.minimumLineSpacing = 10;  layout.itemSize = CGSizeMake(150, 100);  layout.sectionInset = UIEdgeInsetsMake(10, 10, 10, 10);#endif  return [layout autorelease];}- (void)changeLayout:(WaterfallFlowLayout *)layout {  layout.numberOfColumns = 3;}- (void)createCollectionView {  CGRect frame = CGRectMake(0, 20, VIEW_WIDTH, VIEW_HEIGHT-20);  _collectionView = [[UICollectionView alloc] initWithFrame:frame collectionViewLayout:[self createLayout]];  _collectionView.backgroundColor = [UIColor cyanColor];  // 设置代理  _collectionView.delegate = self;  _collectionView.dataSource = self;  // 注册cell 类型 及 复用标识  [_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cellId"];  [self.view addSubview:_collectionView];}#pragma mark - UICollectionViewDataSource- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {  return 102;}- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {  UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cellId" forIndexPath:indexPath];  UILabel * label = nil;  NSArray * array = cell.contentView.subviews;  if (array.count) {    label = array[0];  }else {    label = [[UILabel alloc] init];//    label.frame = cell.bounds;    label.textAlignment = NSTextAlignmentCenter;    label.font = [UIFont systemFontOfSize:50];    [cell.contentView addSubview:label];    [label release];  }  label.frame = cell.bounds;  label.text = [NSString stringWithFormat:@"%ld",indexPath.item];  label.textColor = [UIColor whiteColor];  cell.backgroundColor = RandomColor;  return cell;}- (CGSize) collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {  return CGSizeMake( arc4random()%100+200, 110);}-(CGFloat) WaterfallFlowLayout:(WaterfallFlowLayout *)layout widthForItemAtIndexPath:(NSIndexPath *)indexPath{  return arc4random()%150+50;}-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{  NSLog(@"点击了第 %ld 组，第 %ld 行",indexPath.section,indexPath.row);}- (void)didReceiveMemoryWarning {  [super didReceiveMemoryWarning];}@end