UIPageViewController如何访问不可见页面

Question

I'm using UIPageViewController to implement infinite horizontal scroll between pages with some data. Transition type is set to Scroll.

As soon as user starts horizontal scroll I'm giving back detail view controllers for previous and next pages via viewControllerAfterViewController and viewControllerBeforeViewController delegates.

And at any given time the pageViewController will have a scroll view and three pages inside this scroll view (I can confirm that using Xcode Debug View Hierarchy). How do I get access to invisible pages? .viewControllers property contains only one element corresponding to the visible page.

Answer 1

The default behavior of the UIPageViewController is to dispose of pages not currently visible. Its sort of like a UITableView but the cells are view controllers. The only way to get access to the invisible vcs is to keep strong pointers to them after you build them (probably unwise for an infinite number of pages) or to build a particular one as you need it.

That should make you think about what you plan to do with an invisible vc. If you're thinking about changing how it looks, think again: it doesn't exist. Again, this is a little analogous to a UITableView , where we don't usually change cells directly. Instead, we change our model and the cell changes because it is configured in reaction to the model in cellForRowAtIndexPath :.

Same idea here. Keep a model around that's independent of the page vcs. When they get viewWillAppear , they can configure their views according to the model.