初涉CollectionView

1.初始化一个collectionView

UICollectionViewFlowLayout * layout = [[UICollectionViewFlowLayout alloc] init];
    layout.minimumInteritemSpacing = 5;
    layout.minimumLineSpacing = 5;
    //定义每个item的大小
    layout.itemSize = CGSizeMake(120, 150);
    
    _collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT) collectionViewLayout:layout];
    _collectionView.backgroundColor = [UIColor whiteColor];
    _collectionView.delegate = self;
    _collectionView.dataSource = self;
    
    //注册cell
    [_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cell"];

    [self.view addSubview:_collectionView];

2.实现代理方法

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return _dataArray.count;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    UIImageView * imageV = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
    imageV.image = [UIImage imageNamed:_dataArray[indexPath.row]];
    
    
    UILabel * label = [[UILabel alloc] initWithFrame:CGRectMake(0, 100, 100, 21)];
    label.text = [NSString stringWithFormat:@"第%ld张图", indexPath.row];
    label.textAlignment = NSTextAlignmentCenter;
    //一定要先移除之前的，不然会重叠
    for (UIView * view in cell.contentView.subviews) {
        [view removeFromSuperview];
    }
    [cell.contentView addSubview:imageV];
    [cell.contentView addSubview:label];
    return cell;
    
}