How did they do this? [iPhone layout]

checkout this app:

If you swipe left in main image (the black shoes) you can see another image.

Can anyone try this app (Fashiolista, it's free and signup isn't required) and say me ho开发者_C百科w can I do an effect like that?

Thank you guys.

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I've not tried the app, but the way you usually accomplish that is with UIScrollView. In order to get the swiping-action to work as expected, you have to set pagingEnabled to YES.

The hardest part of implementing something like this is handling limited system resources: you'll run out of memory really quick. So you have to implement a queuing system rather like that used in UITableView. There are a few projects of this sort on GitHub, but I recommend checking out Apple's dev resources on this; I don't remember the link, but I believe in the last WWDC materials, they had info on how to build this properly.

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They seem to be using Core Animation to modify the images' alpha and animate the images out and in.

Check out Introduction to Core Animation Programming Guide.

*edit:

They could also be using UIViews animation API. This is probably even simpler. View Programming Guide - Animations

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Looks like they are lowering the opacity of the content as it scrolls of using core animation and ease out transition