Question

I’m trying to develop a really simple app in xcode 4. It’s a utility app, with one main view and I want to animate a series of photos in the background with a simple alpha fade that loops continuously between 2 or more images.

I found some code in the xcode user documentation, which I’ve modified (below), but I’m new at this and I’m asking how to set the following code into motion in an existing project, where to put what, what outlets to create, etc.:

// This method begins the first animation.

- (IBAction)showHideView:(id)sender

{

    [UIView beginAnimations:@"ShowHideView" context:nil];

    [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];

    [UIView setAnimationDuration:1.0];

    [UIView setAnimationDelegate:self];

    [UIView setAnimationDidStopSelector:@selector(showHideDidStop:finished:context:)];



    // Make the animatable changes.

    secondImageView.alpha = 0.0;



    // Commit the changes and perform the animation.

    [UIView commitAnimations];

}



// Called at the end of the preceding animation.

- (void)showHideDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context

{

    [UIView beginAnimations:@"ShowHideView2" context:nil];

    [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];

    [UIView setAnimationDuration:1.0];

    [UIView setAnimationDelay:1.0];



    secondImageView.alpha = 1.0;



    [UIView commitAnimations];

}

Answer 1

There are really two questions I see, first is the animation code on the right track, and second how to integrate it into an application.

The second part is just basic iPhone 101 stuff for which you’re better off taking a look at the Big Nerd Ranch books for.

For the first part, the way you’re doing animation above is an older style and is more complex than it has to be.

The simplest way is to use animation blocks.

Here is a good introductory post on that, that actually animates alpha of images just as you requested:
http://pragmaticstudio.com/blog/2010/7/28/ios4-blocks-1