UICollectionView 简单的使用和注意事项

UICollectionView 在创建的时候，要给它一个UICollectionViewFlowLayout (不然会崩溃)，就像tableview一样，也要为它注册自定义的cell。

 UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc]init];
    [flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
    //cell间距
    flowLayout.minimumInteritemSpacing = 10.0f;
    //cell行距
    flowLayout.minimumLineSpacing = 20.0f;
    //1.添加FlowLayout
    UICollectionView *collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 64, 320, [UIScreen mainScreen].bounds.size.height - 64) collectionViewLayout:flowLayout];

    //2.为collection 注册cell（自定义的cell）
    [collectionView registerNib:[UINib nibWithNibName:@"CarCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:@"CarCollectionViewCell"];

还要为它设置代理和实现代理方法：

collectionView.backgroundColor = [UIColor whiteColor];
    self.collectionView = collectionView;
    self.collectionView.delegate = self;
    self.collectionView.dataSource = self;
    [self.view addSubview:self.collectionView];

设置cell的大小：

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    CGSize size = CGSizeMake(, );
    return size;
}

设置整体cell在collection中的上下左右边距：

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
    return UIEdgeInsetsMake(30, 20, 0, 20);
}

在cellForItemAtIndexPath中使用自定义的cell，注意自定义cell的xib文件时，要加上identifier：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

    CarCollectionViewCell *cell = (CarCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"CarCollectionViewCell" forIndexPath:indexPath];
 ...
 ...
 ...
return cell;
}