CollectionView添加头尾部

//上下拉头尾部

self.collectionView.footer = [MJRefreshBackNormalFooter footerWithRefreshingTarget:self refreshingAction:@selector(footRequestMore)];

self.collectionView.header = [MJRefreshNormalHeader headerWithRefreshingTarget:self refreshingAction:@selector(headRefreshData)];

//头尾部刷新

[collectionView.header beginRefreshing];//系统自带