【代码笔记】自定义布局实现瀑布流

利用collectionView实现瀑布流的效果，

文件目录如下

动画效果图如下：

//ViewController文件

#import "ViewController.h"
#import "LYWaterFlowLayout.h"
#import "LYWaterCell.h"
#import "LYShopModel.h"

@interface ViewController ()<UICollectionViewDataSource>
@property(nonatomic,strong)NSArray *shops;


@end

@implementation ViewController
 static NSString *ID = @"water";

- (NSArray *)shops{
    
    if (_shops == nil) {
//        1.读取文件
        NSString *path =  [[NSBundle mainBundle ]pathForResource:@"1.plist" ofType:nil];
       NSArray *dictArray =  [NSArray arrayWithContentsOfFile:path];
//        2.字典转模型
        NSMutableArray *tempArray = [NSMutableArray array];
        for (NSDictionary *dict in dictArray) {
            LYShopModel *shop = [LYShopModel shopWithDict:dict];
            [tempArray addObject:shop];
            
        }
        _shops = tempArray;
        
        
        
    }
    return _shops;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
//    0.自定义布局
    LYWaterFlowLayout *waterFlowLayout = [[LYWaterFlowLayout alloc]init];
//    0.1.传递外界数组到内部
    waterFlowLayout.shops = self.shops;
    
//    1.创建collectionView
    UICollectionView *collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) collectionViewLayout:waterFlowLayout];
//    2.设置数据源
    collectionView.dataSource = self;
////    3.设置代理
//    collectionView.delegate = self;
    

//    3.添加
    [self.view addSubview:collectionView];
//    4.注册cell
    [collectionView registerNib:[UINib nibWithNibName:@"LYWaterCell" bundle:nil] forCellWithReuseIdentifier:ID];
    
    
}

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
    
    return  1;
    
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    
    return self.shops.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    
    
//    1.创建cell
   
    LYWaterCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:ID forIndexPath:indexPath];
//    2.赋值
//
//    cell.backgroundColor = [UIColor redColor];
//    2.1获取模型
    LYShopModel *shop = self.shops[indexPath.item];
    cell.shop = shop;
    
    cell.indexPath=indexPath;
//   3.返回cell
    return cell;
    
    
}

@end

//LYWaterCell文件
#import <UIKit/UIKit.h>
@class LYShopModel;

@interface LYWaterCell : UICollectionViewCell
@property(nonatomic,strong)LYShopModel *shop;

@property(nonatomic,strong)NSIndexPath *indexPath;

@end





#import "LYWaterCell.h"
#import "LYShopModel.h"

@interface LYWaterCell()

@property (weak, nonatomic) IBOutlet UIImageView *iconView;
@property (weak, nonatomic) IBOutlet UILabel *priceLabel;

@end
@implementation LYWaterCell
- (void)setShop:(LYShopModel *)shop{
    
    _shop = shop;
  
    self.iconView.image = [UIImage imageNamed:shop.icon];
    //self.priceLabel.text = shop.price;
    
}
-(void)setIndexPath:(NSIndexPath *)indexPath{
    
    _indexPath = indexPath;
    self.priceLabel.text = self.shop.price;
    
}

@end

//LYWaterFlowLayout文件
#import <UIKit/UIKit.h>

@interface LYWaterFlowLayout : UICollectionViewFlowLayout



@property(nonatomic,strong)NSArray *shops;


@end





int const column = 3;
#import "LYWaterFlowLayout.h"
#import "LYShopModel.h"

@interface LYWaterFlowLayout()

@property(nonatomic,strong)NSMutableArray *maxYs;
@end

@implementation LYWaterFlowLayout
- (NSMutableArray *)maxYs{
    
    if (_maxYs == nil) {
        _maxYs = [NSMutableArray array];
        NSLog(@"%@",_maxYs);
        
    }
    
    return _maxYs;
}

/**
 *  用来设置每一个对应位置的item属性
 *
 *  @param indexPath 用来确定每一item具体位置
 *
 *  @return 用来设置每一个item的属性
 */
-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath{
    //NSLog(@"调用了layoutAttributesForItemAtIndexPath");
    //    1.确定上左下右间距
  
    UIEdgeInsets edge = UIEdgeInsetsMake(10, 10, 10, 10);
   //     2.确定宽度
//        2.1确定列数
  
//        2.2确定行间距和列间距
    CGFloat rowMargin = 10;
    CGFloat colMargin = 10;
    
    CGFloat itemW = (self.collectionView.frame.size.width - edge.left - edge.right - (column - 1)*colMargin)/column;    
//        3.确定高度
//        3.1获取对应item的模型
    LYShopModel *shop = self.shops[indexPath.item];
//    itemW/itemh = shop.width/shop.height;

    CGFloat itemH = shop.height *itemW/shop.width;
    
//    CGFloat itmeH = 100+ arc4random_uniform(100);
//        4.确定位置
    
//        4.1获取最小的最大y值
//        4.2用一个值来记录最小的最大y值
    CGFloat minMaxY = MAXFLOAT;
//        4.3记录最小的最大的y值所在的列号；
    NSInteger minMaxCol = 0;
    for (int i = 0; i <column; i ++) {
        CGFloat maxY = [self.maxYs[i]doubleValue];
        if (maxY < minMaxY) {
            minMaxY = maxY;
            minMaxCol = i;
        }
    }
//     4.4设置item的x值
    CGFloat itemX = edge.left + (itemW + colMargin) *minMaxCol;
    CGFloat itemY = minMaxY + rowMargin;
//    5.获取每一个对应位置的item的属性
    UICollectionViewLayoutAttributes *attr = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
//    6.设置属性的frame
    attr.frame = CGRectMake(itemX, itemY, itemW, itemH);
//    7.累加最小的最大的y值
//    minMaxY = CGRectGetMaxY(attr.frame);
    self.maxYs[minMaxCol]= @(CGRectGetMaxY(attr.frame));
    
    
    
//    8.返回属性
    return  attr;

}
/**
 *  用来设置给定范围内所有的属性
 *
 *  @param rect <#rect description#>
 *
 *  @return <#return value description#>
 */
- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{
   // NSLog(@"调用了layoutAttributesForElementsInRect");
//    0.清空原来的所有的值
   // [self.maxYs removeAllObjects];
//    1.设置数组的值
    for (int i = 0 ; i <column;i ++) {
       // [self.maxYs addObject:@(0)];
        self.maxYs[i]=@(0);
    }
    
    
//    2.创建可变数组
    NSMutableArray *attrs = [NSMutableArray array];
    
//
//    3.获取所有的item的属性的个数
    NSInteger count = [self.collectionView numberOfItemsInSection:0];
//    4.遍历多次，添加对应的属性值
    for (int i = 0; i < count; i ++ ) {
        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:0];
        
        UICollectionViewLayoutAttributes *attr = [self layoutAttributesForItemAtIndexPath:indexPath];
    
        [attrs addObject:attr];
     //   NSLog(@"%@",attr);
        
    }
    return attrs;

    
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds{
  //  NSLog(@"调用了shouldInvalidateLayoutForBoundsChange");
    return YES;
}
/**
 *  用来设置collectionView的滚动范围
 *
 *  @return <#return value description#>
 */

- (CGSize)collectionViewContentSize{
    // NSLog(@"调用了collectionViewContentSize");
//    1.获取最大最大y值
    CGFloat maxMaxY = 0;
//    1.1.记录最大的最大y值
    if (self.maxYs.count) {
         maxMaxY = [self.maxYs[0]doubleValue];
        for (int i = 1; i < column; i ++) {
            //        1.2获取每一个值
            CGFloat maxY = [self.maxYs[i]doubleValue];
            if (maxY > maxMaxY) {
                maxMaxY = maxY;
            }
            
        }

    }
    
   
    return CGSizeMake(0, maxMaxY);
    

}

@end

//LYShopModel文件
#import <Foundation/Foundation.h>

@interface LYShopModel : NSObject
@property(nonatomic,copy)NSString *icon;
@property(nonatomic,copy)NSString *price;
@property(nonatomic,assign)int height;
@property(nonatomic,assign)int width;
- (instancetype)initWithDict:(NSDictionary *)dict;
+ (instancetype)shopWithDict:(NSDictionary *)dict;

@end





#import "LYShopModel.h"

@implementation LYShopModel

- (instancetype)initWithDict:(NSDictionary *)dict{
    
    if (self = [super init]) {
        [self setValuesForKeysWithDictionary:dict];
    }
    return self;
}
+ (instancetype)shopWithDict:(NSDictionary *)dict{
    
    return [[self alloc]initWithDict:dict];
}

@end