首先在viewcontroller 中创建collectionView;自定义一个类继承自UICollectionViewFlowLayout代码实现如下;

```Object-C

viewController .m

//

//ViewController.m

//MYCollectionView

//

//Created by dqk on 16/9/2.

//Copyright © 2016年dqk. All rights reserved.

//

#import"ViewController.h"

#import"MYLayout.h"

#import"CollectionViewCell.h"

#define kScreenWidth [UIScreen mainScreen].bounds.size.width

#define kScreenHeight [UIScreen mainScreen].bounds.size.height

@interfaceViewController()

@property(nonatomic,strong)NSMutableArray*arry;

@end

staticNSString*constcellresure =@"cell";

@implementationViewController

-(NSMutableArray*)arry

{

if(_arry==nil)

{

_arry=[[NSMutableArrayalloc]init];

}

return_arry;

}

```Object-C

- (void)viewDidLoad {

[superviewDidLoad];

//测试数据,后期可以根据服务器返回的数据自己设置

_arry=[NSMutableArrayarrayWithObjects:@"100",@"50",@"500",@"30",@"45",@"200",@"70",@"130",@"100",@"50",@"500",@"30",@"45",@"200",@"70",@"130",@"100",@"50",@"500",@"30",@"45",@"200",@"70",@"130",@"100",@"50",@"500",@"30",@"45",@"200",@"70",@"130",@"100",@"50",@"500",@"30",@"45",@"200",@"70",@"130",@"100",@"50",@"500",@"30",@"45",@"200",@"70",@"130",nil];

self.view.backgroundColor=[UIColorwhiteColor];

MYLayout*layout =[[MYLayoutalloc]init];

layout.delegate=self;

//layout.colCount=2;

//

//layout.delegate=self;

UICollectionView*collection =[[UICollectionViewalloc]initWithFrame:self.view.boundscollectionViewLayout:layout];

collection.delegate=self;

collection.dataSource=self;

collection.backgroundColor=[UIColorwhiteColor];

[collectionregisterClass:[UICollectionViewCellclass]forCellWithReuseIdentifier:cellresure];

[self.viewaddSubview:collection];

// Do any additional setup after loading the view, typically from a nib.

}

```

```Object

-C-(NSInteger)collectionView:(UICollectionView*)collectionView numberOfItemsInSection:(NSInteger)section

{

return_arry.count;

}

```

-(UICollectionViewCell*)collectionView:(UICollectionView*)collectionView cellForItemAtIndexPath:(NSIndexPath*)indexPath

{

UICollectionViewCell*cell =[collectionViewdequeueReusableCellWithReuseIdentifier:cellresureforIndexPath:indexPath];

cell.backgroundColor=[UIColorredColor];

UILabel*lal =(UILabel*)[cell.contentViewviewWithTag:100];

if(lal==nil)

{

lal =[[UILabelalloc]init];

lal.tag=100;

[cell.contentViewaddSubview:lal];

}

lal.text=[NSStringstringWithFormat:@"%ld",(long)indexPath.row];

[lalsizeToFit];

returncell;

}

- (CGFloat)waterflowLayout:(MYLayout*)waterflowLayout heightForWidth:(CGFloat)width atIndexPath:(NSIndexPath*)indexPath

{

CGFloatheight =[self.arry[indexPath.row]floatValue];

returnheight;

}

-(NSInteger)waterFlowLayoutColumnCount:(MYLayout*)layout

{

return3;

}

-(CGFloat)waterFlowLayoutColumnSpacing:(MYLayout*)layout

{

return10;

}

-(CGFloat)waterFlowLayoutRowSpacing:(MYLayout*)layout

{

return10;

}

-(UIEdgeInsets)waterFlowLayoutEdgeInsets:(MYLayout*)layout

{

returnUIEdgeInsetsMake(20,20,20,20);

}

//

- (void)didReceiveMemoryWarning {

[superdidReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end

自定义的类MYLayout.h

#import

@classMYLayout;

@protocolMYLayoutDelegate

//此方法必须实现,设置每个item的高度

- (CGFloat)waterflowLayout:(MYLayout*)waterflowLayout heightForWidth:(CGFloat)width atIndexPath:(NSIndexPath*)indexPath;

@optional

//设置collectionView有几列,如果不设置默认是3列

-(NSInteger)waterFlowLayoutColumnCount:(MYLayout*)layout;

//设置每个item的列间距,如果不设置默认10

-(CGFloat)waterFlowLayoutColumnSpacing:(MYLayout*)layout;

//设置每个item的行间距,如果不设置默认10

-(CGFloat)waterFlowLayoutRowSpacing:(MYLayout*)layout;

//设置item距离屏幕上下左右的距离,默认是上下左右都是10;

-(UIEdgeInsets)waterFlowLayoutEdgeInsets:(MYLayout*)layout;

@end

@interfaceMYLayout :UICollectionViewFlowLayout

@property(assign,nonatomic)iddelegate;

@end

自定义的类MYLayout.m

#import"MYLayout.h"

staticNSIntegerconstdefaultColumnCount =3;

staticCGFloatconstdefaucolumspacesing =10;

staticCGFloatconstdedaultRowsping =10;

staticUIEdgeInsetsconstdefaultEdgeInsets = {10,10,10,10};

@interfaceMYLayout();

@property(nonatomic,strong) NSMutableArray * attrArray;

@property(nonatomic,strong) NSMutableArray *maxYArray;

-(NSInteger)columnCount;

-(CGFloat)columSpacing;

-(CGFloat)rowSpacing;

-(UIEdgeInsets)edgeInsets;

@end

@implementationMYLayout

-(NSMutableArray *)attrArray

{

if(_attrArray==nil)

{

_attrArray=[NSMutableArray array];

}

return_attrArray;

}

-(NSMutableArray *)maxYArray

{

if(_maxYArray ==nil)

{

_maxYArray =[NSMutableArray array];

}

return_maxYArray;

}

-(NSInteger)columnCount

{

if([self.delegate respondsToSelector:@selector(waterFlowLayoutColumnCount:)]) {

return[self.delegate waterFlowLayoutColumnCount:self];

}

returndefaultColumnCount;

}

-(CGFloat)columSpacing

{

{

if([self.delegate respondsToSelector:@selector(waterFlowLayoutColumnSpacing:)]) {

return[self.delegate waterFlowLayoutColumnSpacing:self];

}

returndefaucolumspacesing;

}

}

-(CGFloat)rowSpacing

{

{

if([self.delegate respondsToSelector:@selector(waterFlowLayoutRowSpacing:)]) {

return[self.delegate waterFlowLayoutRowSpacing:self];

}

returndedaultRowsping;

}

}

-(UIEdgeInsets)edgeInsets

{

{

if([self.delegate respondsToSelector:@selector(waterFlowLayoutEdgeInsets:)]) {

return[self.delegate waterFlowLayoutEdgeInsets:self];

}

returndefaultEdgeInsets;

}

}

-(void)prepareLayout

{

[superprepareLayout];

[self.attrArray removeAllObjects];

[self.maxYArray removeAllObjects];

for(inti =0; i <[selfcolumnCount]; i ++)

{

[self.maxYArray addObject:@([selfedgeInsets].top)];

}

NSInteger itemCount =[self.collectionView numberOfItemsInSection:0];

for(inti =0; i

{

NSIndexPath *indepath =[NSIndexPath indexPathForRow:i inSection:0];

[self.attrArray addObject:[selflayoutAttributesForItemAtIndexPath:indepath ]];

}

}

-(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect

{

returnself.attrArray;

}

-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath

{

UICollectionViewLayoutAttributes*attabuest =[UICollectionViewLayoutAttributeslayoutAttributesForCellWithIndexPath:indexPath];

NSInteger__blockminHegihtColumn =0;

NSInteger__blockminheight = [self.maxYArray[minHegihtColumn]floatValue];

[self.maxYArrayenumerateObjectsUsingBlock:^(id_Nonnullobj,NSUIntegeridx,BOOL*_Nonnullstop) {

CGFloatcolumnHeight = [(NSNumber*)objfloatValue];

if(minheight>columnHeight)

{

minheight =columnHeight;

minHegihtColumn=idx;

}

}];

UIEdgeInsetsedgeInsets =[selfedgeInsets];

CGFloatwidth =(CGRectGetWidth(self.collectionView.frame)-edgeInsets.left-edgeInsets.right-[selfcolumSpacing]*([selfcolumnCount]-1))/[selfcolumnCount];

CGFloatheight = [self.delegatewaterflowLayout:selfheightForWidth:widthatIndexPath:indexPath];

CGFloatorginX =edgeInsets.left +minHegihtColumn *(width +[selfcolumSpacing]);

CGFloat orginY = minheight;

if(orginY != edgeInsets.top)

{

orginY +=[selfrowSpacing];

}

attabuest.frame =CGRectMake(orginX,orginY,width,height);

self.maxYArray[minHegihtColumn]=@(CGRectGetMaxY(attabuest.frame));

returnattabuest;

}

-(CGSize)collectionViewContentSize

{

NSInteger__blockmaxheight =0;

[self.maxYArray enumerateObjectsUsingBlock:^(id_Nonnullobj, NSUInteger idx,BOOL*_Nonnullstop) {

CGFloat columnHeight = [(NSNumber *)obj floatValue];

if(maxheight

{

maxheight =columnHeight;

}

}];

returnCGSizeMake(0, maxheight +[selfedgeInsets].bottom);

}

@end

```Object-C

到此瀑布流已经实现