UICollection视图更新回调

Question

I have been googling about this but is there an easy way to catch the event when data in collection has been added or removed? I have collection view containing list of images in one line horizontally and user can scroll right or left to see the images. I want to bring the scroll position to the first image from the right when another image is added. I can do that by using scrollRectToVisible but I am not sure where I can call this function to scroll. I was trying to find an event fired when the collection view is modified.

Answer 1

And how exactly are you adding the image? Are you adding a new cell? If yes then you must be updating the layout parameters and invalidating the layout, you can add your scroll there. And if you are just adding an image on the already existing cell, then on what gesture are you doing it? Gesture Handler is a good place in that case.

Answer 2

This is bad architecture. Instead of the relevant parts of your controller communicating with one another, you're trying to bounce the information off your view layer. Don't do this. This is not what the view layer is for. When you have new information and update the collection view, update its scroll position as well.