Question

I’m designing the interface for an iOS app in which there are both hierarchical navigation modes and arbitrary view-swapping modes. The layout of any given view in one mode is distinct from that of the corresponding view in the other mode.

I want the user to be able to switch back and forth between these modes. Say an isolated subview has a corresponding detail view that is 2 levels down in the UINavigationController’s hierarchy. The user should be able to switch directly to that navigation detail view. From there, he should be able either to navigate up and down the UINavigationController hierarchy or to switch back to the isolated subview from which he came.

UINavigationController has a method popToViewController:animated: that will let you skip levels as you navigate back up the hierarchy, but it has no corresponding pushToViewController:animated: that would let you jump directly to a lower level in the hierarchy. That makes sense — the nav controller must push the intervening view/s onto the stack before it displays the target view. But the regular push methods display the intervening view/s, which I assume will cause a visual flash as well as exacting a performance hit.

If I simulate pushToViewController by calling pushViewController twice consecutively, with animated:NO for the intervening view and with the intervening view set temporarily to be transparent, will I get reasonable performance? Or, when the nav mode is requested, should I place the nav controller’s stack behind the isolated views, do the multiple calls to pushViewController, and then move the nav controller to the front? Or should I forgo the use of UINavigationController altogether and do all the table-view-style navigation manually via UIView’s add/remove/insert/exchangeSubview?

Answer 1

I believe setViewControllers:animated: is going to help you do what you want.

When you want to add several view controllers to the stack and directly go to the last one, you can explicitly set the entire stack and have the UINavigationController animate navigation directly to the last one.

NSMutableArray* controllers = [NSMutableArray arrayWithArray:[self.navigationController viewControllers]];
[controllers addObject:newController1];
[controllers addObject:newController2];
[self.navigationController setViewControllers:controllers animated:YES];

This will push newController1 and newController2 to your view stack and animate a transition to newController2.