Animation is slow on iPhone
- by Anthony Chan
I'm developing an app that would display images and change them according to the user's action. I've created a subclass of UIView to contain an image, an index number and an array of image names. The code is like this:
@interface CustomPic : UIView {
UIImageView *pic;
NSInteger index;
NSMutableArray *picNames; //<-- an array of NSString
}
And in the implementation part, it has a method to change the image using a dissolve effect.
- (void)nextPic {
index++;
if (index >= [picNames count]) {
index = 0;
}
UIImageView *temp = pic;
pic.image = [UIImage imageNamed:[picNames objectAtIndex:index]];
temp.alpha = 0;
[UIView beginAnimations:nil context:nil];
[UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
[UIView setAnimationDuration:0.25];
pic.alpha = 0;
temp.alpha = 1;
[UIView commitAnimations];
}
In the viewController, there are several CustomPic which would change the images depends on users' choice. The images would change as expected with the fade in/out effect, but the animation performance is really bad. I've tested it on an iPhone 3G, the Instruments shows that the animation is only 2-3FPS! I tried many methods to simplify and modify the codes but with no hope. Is there something wrong in my code or in my concept? Thanks for any help.
P.S. all the images are 320*480 PNGs with a max size of 15KB.
