在开发过程中我们遇到很多需要用到瀑布流的地方,比如商城类app下面我就详细说一下自定义瀑布流自定义cell宽高,将他整成活的,其实有很多种方式,我先讲一下这个稍微复杂一些的.

#import "waterfallFlowViewController.h"
#import "Header.h"
@interface waterfallFlowViewController ()<UICollectionViewDelegate,UICollectionViewDataSource,CustomLayoutDelegate>
{
    NSArray *array;
}
@end

@implementation waterfallFlowViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor=[UIColor whiteColor];
    
    array =@[@(30),@(80),@(110),@(60),@(150),@(220),@(40),@(90),@(350),@(200),@(260),@(170),@(40),@(90),@(350),@(200),@(260),@(170),@(80),@(110),@(60),@(150),@(220),@(40),@(90)];
    CustomLayout *layout =[[CustomLayout alloc]init];
    layout.delegate=self;
    self.collection_view=[[UICollectionView alloc]initWithFrame:self.view.frame collectionViewLayout:layout];
    self.collection_view.backgroundColor=[UIColor whiteColor];
    self.collection_view.delegate=self;
    self.collection_view.dataSource=self;
    [self.collection_view registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"123"];
    [self.view addSubview:self.collection_view];

    // Do any additional setup after loading the view.
}
//返回区数
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}
//每区返回的行数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return array.count;
}
//构建单元格
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell =[collectionView dequeueReusableCellWithReuseIdentifier:@"123" forIndexPath:indexPath];
    //随机颜色
    cell.backgroundColor =[UIColor colorWithRed:arc4random()%255/255.0 green:arc4random()%255/255.0 blue:arc4random()%255/255.0 alpha:1];
    
    return cell;
}
-(CGSize)collectionView:(nonnull UICollectionView *)collectionView layout:(nonnull UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(nonnull NSIndexPath *)indexPath
{
    CGFloat height =[[array objectAtIndex:indexPath.row]floatValue];
    CGSize size =CGSizeMake(150, height);
    return size;
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end

下面再说一下自定义cell高度的方式(点h文件)

#import <UIKit/UIKit.h>
//开启代理的主要用途就是为了获得每个cell对应的高度
@protocol CustomLayoutDelegate <NSObject>

@required

-(CGSize)collectionView:(nonnull UICollectionView *)collectionView layout:(nonnull UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(nonnull NSIndexPath *)indexPath;

@end

//如果自定义表明当前layout是完全重新绘制的 一定要实现对应的属性
@interface CustomLayout : UICollectionViewLayout
//定义拥有的属性
//宽度
@property(nonatomic,assign)NSInteger itemWidth;
//数量>>>单元格
@property(nonatomic,assign)NSInteger cellCount;
//区域部分 left  top  right buttom
@property(nonatomic,assign)UIEdgeInsets sectionInsets;

@property(nonatomic,assign)id<CustomLayoutDelegate>delegate;
@end

其次我再说下点m,看自己的理解能力 了

#import "CustomLayout.h"

@implementation CustomLayout
{
    //起点
    float _x;
    //左侧 y
    float _leftY;
    //右侧
    float _rightY;
}
//相当于init
//首先，-(void)prepareLayout将被调用，默认下该方法什么没做，但是在自己的子类实现中，一般在该方法中设定一些必要的layout的结构和初始需要的参数等。
-(void)prepareLayout
{
    NSLog(@"------%s",__FUNCTION__);
    //赋值
    self.delegate =(id<CustomLayoutDelegate>)self.collectionView.delegate;
    //VIewcontroller的对象
    //self.collectionView.delegate =self;
    
    self.itemWidth =150;
    
    self.sectionInsets =UIEdgeInsetsMake(5, 5, 5, 5);
    //拿个数   self.collectionView
    //返回对应区的cell个数
    self.cellCount =[self.collectionView numberOfItemsInSection:0];
    NSLog(@"----%ld",self.cellCount);
}
//返回collectionView对应的内容尺寸
-(CGSize)collectionViewContentSize
{
    return CGSizeMake(320, _leftY>_rightY?_leftY:_rightY);
}
//返回一个装attributes的数组
//UICollectionViewLayoutAttributes 当前cell的属性
- (nullable NSArray<__kindof UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect
{
    _x =0;
    _leftY =0;
    _rightY =0;
    //用来装attribute将来返回出去
    NSMutableArray *attributes =[NSMutableArray array];
       //从当前的colletionView上把对应的cell的attribute取出来
    for (int i=0; i<self.cellCount; i++)
    {
        NSIndexPath *indexPath =[NSIndexPath indexPathForItem:i inSection:0];
        
    UICollectionViewLayoutAttributes *attribute =[self layoutAttributesForItemAtIndexPath:indexPath];
        
        [attributes addObject:attribute];
    }
    return attributes;
 
 
}
//通过所在的indexPath确定位置。
- (nullable UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    //创建一个空白的attributes
    UICollectionViewLayoutAttributes *attribute = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
    //通过协议方法来捕捉每个cell所需要的size
    CGSize itemSize =[self.delegate collectionView:self.collectionView layout:self sizeForItemAtIndexPath:indexPath];
    
    CGFloat itemHeight =itemSize.height;
    /*
     位置
     x =5(左)  右:itemWidth+15
     宽:       高(y)
     */
    if (_rightY <_leftY)
    {
        //往右侧添加按钮
        _x =self.itemWidth+3*self.sectionInsets.left;
        
        _rightY +=self.sectionInsets.top;
        
         attribute.frame =CGRectMake(_x, _rightY, self.itemWidth, itemHeight);
        
        _rightY +=itemHeight;
    }
    else
    {
        //左侧
        _x =self.sectionInsets.left;
        
        _leftY +=self.sectionInsets.top;
        
        attribute.frame =CGRectMake(_x, _leftY, self.itemWidth, itemHeight);
        //记录一下当前_leftY的新值(_left+=高度)
        _leftY +=itemHeight;
    }
    return attribute;
}
@end

效果图

屏幕快照 2017-01-12 上午9.37.12.png