FWCollectionViewDialLayout根据Dial degree布局UICollectionViewCell，cell的中心点是对dial degree的平均。如何使用拨号布局覆盖布局实例方法：

  • (UICollectionViewLayoutAttributes t)layoutAttributesForItemAtIndexPath:(NSIndexPath )indexPath;

FWCollectionViewDialLayout *layout = [[FWCollectionViewDialLayout alloc] initWithDegree:120 cellSize:CGSizeMake(50, 50)];

[self.collectionView setCollectionViewLayout:layout];