Question

So I am just beginning recently developing some simple apps for the iphone. I will say that I am fairly sure I don’t have a strong understanding of programming for multiple views yet, but I am trying to learn as I go.

I have a program that started as a plain window based application so i could hand write everything in hopes of learning more about what i am doing. I have a single view controller that acts to load and release views as requested from each of the other view controllers. No elements persist from one view to the other.

I have that working fine currently, but I wanted to add animations to the view changing. A simple push animation was my goal. One view pushes out as the new view pushes in.

Looking into CATransitions and trying that, I have a working version (currently for pushing top/bottom)

        [thisView.view removeFromSuperview];
        [thisView release];
        thisView = [[MenuViewController alloc] initWithNibName:@"MenuView" bundle:nil];
        [self.view addSubview:thisView.view];   

        CATransition *animation = [CATransition animation];
        [animation setDuration:6.3];
        [animation setType:kCATransitionPush];
        [animation setSubtype:kCATransitionFromTop];
        [animation setRemovedOnCompletion:YES];
        [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];
        [[self.view layer] addAnimation:animation forKey:nil];

as far as I can tell this is pretty standard code for using CATransition and it works to do what I need, one view gets pushed up as the other view comes in. However my problem is that there seems to be a fade that happens to each view as they come in or go out respectively.

As such – in this example; as the menu pushes up from the bottom, it will very slowly fade in from white, and as the previous view leaves the screen it will slowly fade to white.

Note that the duration is set to 6 so that the fading is dramatic.

Is there a way to remove the fading here so that each view remains solid on the way in and the way out? Or have I missed the mark completely in this route that I am taking?

I appreciate any help. Apologies I have been long winded.

Answer 1

I have never been able to find a solution to this problem, but I can offer a reasonable workaround. What’s happening is it isn’t fading to white, but fading to transparent, and the window background (or whatever view is behind) is white. There are a couple ways to get around this:

1. Change the window background color. If both views you’re fading between have the same solid background color, then this will look pretty good.

2. Don’t render a background in each view (“MenuView,” for example), but rather have a shared background view that’s under those views at all times.

Note that this will not work in all circumstances — grouped UITableViews, for example, are always completely opaque.

(As I side note, I assume that you aren’t build a navigation-based application, in which case all the animation should be handled automatically.)

You also might want to consider the looking into the UIView method setAnimationTransition:forView:cache: if you haven’t already as another way to transition between views (although it cannot do a sliding animation, if you are set on that).