Question

I m brand new in iPhone animation feature. I wrote a simple testing program to spin a red rectangle; however, the animation doesn t act at all. What s wrong with my code? Thanks a lot...

//.h
#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>

#define DegreesToRadians(X) (M_PI*X/180.0)

//.m
- (void)viewDidLoad {
    [super viewDidLoad];
    CGRect theRect = CGRectMake(0,0,100,100);
    UIView *theBox = [[UIView alloc] initWithFrame:theRect];
    theBox.backgroundColor = [UIColor redColor];
    [self.view addSubview:theBox];
    CALayer *theLayer = [theBox layer];
    [self spinLayer:theLayer];

}

-(CAAnimation *)animationForSpinning{
    float radians = DegreesToRadians(360);
    CATransform3D theTransform = CATransform3DMakeRotation(radians, 0, 0, 1.0);
    CABasicAnimation *theAnimation = [CABasicAnimation animationWithKeyPath:@"transform"];
    theAnimation.toValue = [NSValue valueWithCATransform3D:theTransform];
    theAnimation.duration = 2;  // 2 seconds
    theAnimation.repeatCount = 10000;
    theAnimation.cumulative = YES;

    return theAnimation;    
}

-(void)spinLayer:(CALayer *)theLayer{
    CAAnimation *spinningAnimation = [self animationForSpinning];
    [theLayer addAnimation:spinningAnimation forKey:@"opacity"];

    // trigger the animation
    theLayer.opacity = 0.99;
}

Answer 1

Your animation is not running because Core Animation sees a transform of 360 degrees being the same as your original image, so it does nothing.

The easiest way to handle a 360 degree rotation is described in this answer to this question, where you set up your CABasicAnimation to animate the transform.rotation.z property from 0 to 2 * pi radians.

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