Zooming out for the first time in UIScrollView is not smooth

Question

Hi,

I created UIScrollView and added UIView with lots of tiled UIButtons in the UIView. My problem is, when every time I zoom out the content using zoomToRect method of UIScrollView to the minimum scale I set, the zooming out is not smooth. But zoom-in and zoom-out for the second time is smooth. How can I make the zooming out for the first time to smooth zooming?

Thanks.

Answer 1

The slow initial zoom is obviously due to the phone allocating all the UIButtons the first time it has to draw them. They should be allocated incrementally or before the user starts to interact with them.

What are you doing that requires so much loading and drawing? It doesn't sound like the user would be able to interact with the million or so buttons they might be viewing.

I would suggest adding a pile of code to a UIScrollView Sub Class that makes it aware of it's content size, and it can then init the required UIButtons before the user starts to interact with your UIScrollview, or incrementally as I said.

There is demo code called 'Tiling' that sheds some light on using UIScrollViews to manage large content. It's quite complex, but a very complete demo that I'm sure most projects implement if they handle UIScrollViews with tiled content.