iOS---UICollectlionView 的使用

UICollectlionView继承自UIScrollerview，跟tableview的使用很相似。

下面是UIcollectionView的一些属性和代理方法。

#import "ViewController.h"
#import "GoodsCollectionViewCell.h"

@interface ViewController ()
@property(nonatomic,strong)NSMutableArray *dataArray;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor lightGrayColor];
    _dataArray = [NSMutableArray array];
    for (int i = ; i < ; i ++) {
        [_dataArray addObject:[NSString stringWithFormat:@"%d",i]];
    }

    //确定是水平滚动，还是垂直滚动
    UICollectionViewFlowLayout *flowLayout=[[UICollectionViewFlowLayout alloc] init];
    flowLayout.scrollDirection = UICollectionViewScrollDirectionVertical;

    self.collectionView=[[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:flowLayout];
    self.collectionView.dataSource=self;
    self.collectionView.delegate=self;
    [self.collectionView setBackgroundColor:[UIColor clearColor]];

    //注册Cell，必须要有
    [self.collectionView registerNib:[UINib nibWithNibName:@"GoodsCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:@"GoodsCollectionViewCell"];

    [self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];
    [self.view addSubview:self.collectionView];

}

#pragma mark -- UICollectionViewDataSource

//定义展示的UICollectionViewCell的个数
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return ;
}

//定义展示的Section的个数
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return ;
}

//每个UICollectionView展示的内容
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    GoodsCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"GoodsCollectionViewCell" forIndexPath:indexPath];
    cell.goodsImageView.image = [UIImage imageNamed:_dataArray[indexPath.row]];
    cell.backgroundColor = [UIColor whiteColor];
    return cell;
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    UICollectionReusableView *headReusableView;
    //此处是headerView
    if (kind == UICollectionElementKindSectionHeader) {
        headReusableView = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"header" forIndexPath:indexPath];
        //防止复用时候重复添加title
        [headReusableView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];

        if (indexPath.section == ) {
            UIView *headerADView = [[ UIView alloc]initWithFrame:CGRectMake(, , self.view.frame.size. width, )];
            headerADView.backgroundColor = [UIColor yellowColor];
            UILabel *titleADLabel = [[UILabel alloc]initWithFrame:CGRectMake(, , self.view.frame.size. width - , )];
            titleADLabel.text = @"这个是广告位";

            UILabel *titleLabel = [[UILabel alloc]initWithFrame:CGRectMake(, , self.view.frame.size. width - , )];
            titleLabel.text = @"推荐商品";
            headReusableView.backgroundColor = [UIColor colorWithWhite:. alpha:];

            [headerADView addSubview:titleADLabel];
            [headReusableView addSubview:headerADView];
            [headReusableView addSubview:titleLabel];
        }else{

            UILabel *titleLabel = [[UILabel alloc]initWithFrame:CGRectMake(, , self.view.frame.size. width - , )];
            titleLabel.text = @"推荐商品";
            headReusableView.backgroundColor = [UIColor colorWithWhite:. alpha:];
            [headReusableView addSubview:titleLabel];
        }
    }
    return headReusableView;
}

//执行的 headerView 代理  返回 headerView 的高度
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
    if (section == ) {
        return CGSizeMake(,  + );

    }
    return CGSizeMake(, );
}

#pragma mark --UICollectionViewDelegateFlowLayout

//定义每个Item 的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake(self.view.frame.size.width / 3.0, );
}

//定义每个UICollectionView 的 margin
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(, , , );
}

#pragma mark --UICollectionViewDelegate

//UICollectionView被选中时调用的方法
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    GoodsCollectionViewCell * cell = (GoodsCollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
    //临时改变个颜色，看好，只是临时改变的。如果要永久改变，可以先改数据源，然后在cellForItemAtIndexPath中控制。（和UITableView差不多吧！O(∩_∩)O~）
    cell.backgroundColor = [UIColor greenColor];
}

//返回这个UICollectionView是否可以被选择
-(BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

// 两个cell之间的最小间距，是由API自动计算的，只有当间距小于该值时，cell会进行换行
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
    return ;
}

// 两行之间的最小间距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return ;
}

@end

注意：

1.定义collectionView的头文件的时候，需要先注册。

2.collectionView每一行显示几个cell是根据cell 的宽度自动显示的。如：scrollerview的宽度为320，cell宽度为 90， 3 * 90 = 270 < 320 , 4 * 90 = 360 > 320,这个时候就显示3个cell。

3.每一行cell的位置的微调可以通过代理方法进行调整。