UICollectionView must be initialized with a non-nil layout parameter

UICollectionView must be initialized with a non-nil layout parameter

UICollectonView必须传入不为空的layout参数来初始化
解决方法：重写init方法

-(id)init{

    UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayoutalloc]init];

    if (self=[superinitWithCollectionViewLayout:layout])
{

    }

    return
self;

}