UICollectionView基本使用

#import "ViewController.h"

@interface ViewController ()<UICollectionViewDataSource,UICollectionViewDelegateFlowLayout>

@property (nonatomic,strong) UICollectionView *collectionView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    //有了UICollectionViewDelegateFlowLayout代理方法，设置layout的属性不起作用
    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
    layout.minimumLineSpacing = 30;
    layout.minimumInteritemSpacing = 2;
    layout.itemSize = CGSizeMake(50, 50);
    layout.scrollDirection = UICollectionViewScrollDirectionVertical;
    layout.sectionInset = UIEdgeInsetsMake(10, 20, 30, 40);
    layout.headerReferenceSize = CGSizeMake(0, 100);
    layout.footerReferenceSize = CGSizeMake(0, 50);
    
    self.collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height) collectionViewLayout:layout];
    self.collectionView.backgroundColor = [UIColor redColor];
    self.collectionView.delegate = self;
    self.collectionView.dataSource = self;
    [self.view addSubview:self.collectionView];
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"id"];
    [self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];
    [self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"footer"];
    
}

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
    return 2;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return 20;
}


- ( UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"id" forIndexPath:indexPath];
    cell.backgroundColor = [UIColor greenColor];
    return cell;
    
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
    
    if (kind == UICollectionElementKindSectionHeader){
        UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"header" forIndexPath:indexPath];
        headerView.backgroundColor = [UIColor yellowColor];
        UILabel *titleLabel = [[UILabel alloc]initWithFrame:headerView.bounds];
        titleLabel.text = [NSString stringWithFormat:@"第%ld个分区的区头",(long)indexPath.section];
        [headerView addSubview:titleLabel];
        return headerView;
    }else if(kind == UICollectionElementKindSectionFooter){
        UICollectionReusableView *footerView = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"footer" forIndexPath:indexPath];
        footerView.backgroundColor = [UIColor blueColor];
        UILabel *titleLabel = [[UILabel alloc]initWithFrame:footerView.bounds];
        titleLabel.text = [NSString stringWithFormat:@"第%ld个分区的区尾",(long)indexPath.section];
        [footerView addSubview:titleLabel];
        return footerView;
    }
    return nil;
    
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
    return CGSizeMake(100, 100);
}
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
    return UIEdgeInsetsMake(1, 1, 1, 1);
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section{
    return 1;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section{
    return 1;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section{
    return CGSizeMake(0, 20);
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section{
    return CGSizeMake(0, 20);
}



@end