Changing Background Color of UIView - objective-c

Question

See where that ugly yellow is? I need that color to be changing... a lot. Kind of like a trippy kalidascope thing, but with one color the entire time. A lot like the default OS X Spectrum screensaver. How should I go about doing this? Objective-C would seem like a huge CPU hog. Would it be possible for me to put an OpenGL background into something like this? Would love a push in the right direction.

Answer 1

Well you can schedule a function call for like half a second and then change the background color there like this
[NSTimer scheduledTimerWithTimeInterval:0.3f target:self selector:#selector(someMethod) userInfo:nil repeats:YES];
- (void)someMethod
{
self.view.backgroundColor = [UIColor redColor];
}
But this will change the color your background view to only red, so in order to change the color to something else you can declare a class variable or more than one to change the your background color. And in the selector method you can change their value to get some cool effects. You can do something like this.
self.view.backgroundColor = [UIColor colorWithRed:x green:y blue:z alpha:1.0f];
x += 0.01f;
y += 0.02f;
z += 0.04f;
if(x >= 1)
x = 0.01f;
if(y >= 1)
y = 0.02f;
if(z >= 1)
z = 0.04f;

Answer 2

Try the simplest thing first: just set the backgroundColor property on that view and then use performSelector:withObject:afterDelay: to change to the next color after a suitable delay.
Unless you're doing the whole screen with OpenGL, it's not likely to be any faster that way. The bottleneck is most likely compositing the "ball" image and text over the background rather than the creation of a solid-color background. Profile it, instead of guessing or relying on my guessing.

Answer 3

Let's assume the foreground material has transparency. Then we can have a solid view behind it that occupies the entire screen, and we see that view's color thru the foreground material. Then it suffices to change that background view's color. If you wish to animate this change in background color, change the view's layer's backgroundColor (to a CGColor); the effect will automatically be animated. You'll need to link to QuartzCore.framework and import <QuartzCore/QuartzCore.h>, and then you'll be able to say:
theView.layer.backgroundColor = [[UIColor redColor] CGColor];
You can modify this color animation; for example, you can dictate its duration (how fast or slow the color changes) by setting the animation duration for CATransaction (see the CATransaction class methods). I can imagine you'd have a repeating NSTimer, where every time the timer fires you'd do another color-change animation.