使用 reloadData 方法重新加载 UICollectionView 会在重新加载数据之前立即返回 [英] Reloading a UICollectionView using reloadData method returns immediately before reloading data

问题描述

我需要知道何时重新加载 UICollectionView 以便之后配置单元格(因为我不是单元格的数据源 - 否则已经完成了......)

I need to know when reloading a UICollectionView has completed in order to configure cells afterwards (because I am not the data source for the cells - other wise would have done it already...)

我尝试过诸如

[self.collectionView reloadData];
[self configure cells]; // BOOM! cells are nil

我也尝试过使用

[self.collectionView performBatchUpdates:^{
  [self.collectionView reloadData];
    } completion:^(BOOL finished) {
        // notify that completed and do the configuration now
  }];

但是当我重新加载数据时，我遇到了崩溃.

but when I reload the data I am getting crashes.

如何将数据重新加载到集合中，并且仅在完成重新加载后 - 执行特定的完成处理程序

How can I reload the data into the collection, and only when it has finished reloading - do a particular completion handler

推荐答案

这是由于在 layoutSubviews 期间添加的单元格不在 reloadData 处.由于 layoutSubviews 在 reloadData 之后的下一个运行循环传递期间执行，因此您的单元格为空.尝试这样做:

This is caused by cells being added during layoutSubviews not at reloadData. Since layoutSubviews is performed during next run loop pass after reloadData your cells are empty. Try doing this:

[self.collectionView reloadData];
[self.collectionView layoutIfNeeded];
[self configure cells]; 

我有类似的问题，并以这种方式解决.

I had similar issue and resolved it this way.

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