通過點擊來實現collectionView的滑動
有系統的方法可以實現
scrollToItemAtIndexPath: atScrollPosition: animated:

scrollPosition這個參數控制cell具體停留在上下左右中到底哪個位置

UICollectionViewScrollPositionNone                 = 0,
    
// The vertical positions are mutually exclusive to each other, but are bitwise or-able with the horizontal scroll positions.
// Combining positions from the same grouping (horizontal or vertical) will result in an NSInvalidArgumentException.
    UICollectionViewScrollPositionTop                  = 1 << 0,
    UICollectionViewScrollPositionCenteredVertically   = 1 << 1,
    UICollectionViewScrollPositionBottom               = 1 << 2,
    
// Likewise, the horizontal positions are mutually exclusive to each other.
    UICollectionViewScrollPositionLeft                 = 1 << 3,
    UICollectionViewScrollPositionCenteredHorizontally = 1 << 4,
    UICollectionViewScrollPositionRight                = 1 << 5

例如我寫的collectionView為橫向滑動,需要點擊兩邊cell都可以左右滑動,代碼如下

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    
    [collectionView scrollToItemAtIndexPath:indexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:YES];
    
}

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