UICollectionView的综合布局

#import "ViewController.h"
#import "CollectionViewCell.h"
#import "CollectionReusableView.h"

@interface ViewController () <UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    flowLayout.minimumInteritemSpacing = 0;
    UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:self.view.bounds collectionViewLayout:flowLayout];
    collectionView.backgroundColor = [UIColor whiteColor];
    collectionView.delegate = self;
    collectionView.dataSource = self;
    [self.view addSubview:collectionView];
    
    [collectionView registerNib:[UINib nibWithNibName:NSStringFromClass([CollectionViewCell class]) bundle:nil] forCellWithReuseIdentifier:@"cell"];
    
    [collectionView registerNib:[UINib nibWithNibName:NSStringFromClass([CollectionReusableView class]) bundle:nil] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"headcell"];
}

#pragma mark - 数据源
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 4;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    if (section == 0) {
        return 3;
    } else if(section ==3) {
        return 20;
    }
    return 4;
}

- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    if (indexPath.section == 0 && indexPath.row == 1) {
        cell.frame = CGRectMake(self.view.frame.size.width / 3 , 30, self.view.frame.size.width*2 / 3 -10, 50);
    }else if(indexPath.section == 0 && indexPath.row == 2){
        cell.frame = CGRectMake(self.view.frame.size.width / 3, 90, self.view.frame.size.width*2 / 3-10, 50);
    }
    
    return cell;
}

#pragma mark - cell的样式
- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout *)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    CGSize itemSize;
    if (indexPath.section == 0) {
        
        if (indexPath.row == 0) {
            itemSize = CGSizeMake(self.view.bounds.size.width/3-30, 110);
        }else
        {
            itemSize = CGSizeMake(self.view.bounds.size.width/3-30, 50);
        }
        return itemSize;
        
    } else if (indexPath.section == 3) {
        
        itemSize = CGSizeMake(self.view.bounds.size.width/3-20, 200);
        return itemSize;
        
    } else {
        float viewW = self.view.frame.size.width / 3 - 10;
        CGSize itemSize1 = CGSizeMake(viewW, 50);
        return itemSize1;
    }
    
}

#pragma mark - 头部样式
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
    
    UICollectionReusableView *reusableView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"headcell" forIndexPath:indexPath];
    
    return reusableView;
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
    return CGSizeMake(self.view.frame.size.width, 30);
}

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
    return UIEdgeInsetsMake(0, 10, 0, 10);
}