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Problem:
Sometimes, I made the collectionview reloaded its data source to call [collectionView reloadData] and it did reload the cell and data in itself;however,
it didn't update its view(its contentsize isn't updated) immediately (might update in next run loop, so it looked like cropped at some time). How to fixed it?
My Way:
I just used [collectionView layoutIfNeeded] after calling [collectionView layoutIfNeeded] immediately.
Quotes from objc.io's post:
You can trigger this pass by calling
setNeedsLayout, which does not actually go ahead and apply the layout immediately, but takes note of your request for later.
To force the system to update the layout of a view tree immediately, you can call
layoutIfNeeded/layoutSubtreeIfNeeded(on iOS and OS X respectively)