Por desgracia, el color no se animan con animaciones UIView. Las respuestas a this question brindan algunas buenas soluciones sin usar Core Animation.
Si no les importa usar un CATextLayer en lugar de un UILabel, entonces el color (y la escala en su ejemplo) puede ser animado como esto:
#import <QuartzCore/QuartzCore.h>
//Also need to add QuartzCore framework to project (as well as the import).
//
-(void)animateTextLayer {
CGFloat animationDuration = 5;
CATextLayer *textLayer = [CATextLayer layer];
[textLayer setString:@"Hello World"];
[textLayer setForegroundColor:[UIColor purpleColor].CGColor];
[textLayer setFontSize:30];
[textLayer setFrame:CGRectMake(20, 200, 300, 40)];
[[self.view layer] addSublayer:textLayer];
CABasicAnimation *colorAnimation = [CABasicAnimation
animationWithKeyPath:@"foregroundColor"];
colorAnimation.duration = animationDuration;
colorAnimation.fillMode = kCAFillModeForwards;
colorAnimation.removedOnCompletion = NO;
colorAnimation.fromValue = (id)[UIColor purpleColor].CGColor;
colorAnimation.toValue = (id)[UIColor greenColor].CGColor;
colorAnimation.timingFunction = [CAMediaTimingFunction
functionWithName:kCAMediaTimingFunctionLinear];
CAKeyframeAnimation *scaleAnimation = [CAKeyframeAnimation
animationWithKeyPath:@"transform"];
NSArray *scaleValues = [NSArray arrayWithObjects:
[NSValue valueWithCATransform3D:CATransform3DScale(textLayer.transform, 1, 1, 1)],
[NSValue valueWithCATransform3D:CATransform3DScale(textLayer.transform, 1.5, 1.5, 1)],
[NSValue valueWithCATransform3D:CATransform3DScale(textLayer.transform, 0.5, 0.5, 1)], nil];
[scaleAnimation setValues:scaleValues];
scaleAnimation.fillMode = kCAFillModeForwards;
scaleAnimation.removedOnCompletion = NO;
CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
animationGroup.duration = animationDuration;
animationGroup.timingFunction = [CAMediaTimingFunction
functionWithName:kCAMediaTimingFunctionLinear];
animationGroup.fillMode = kCAFillModeForwards;
animationGroup.removedOnCompletion = NO;
animationGroup.animations =
[NSArray arrayWithObjects:colorAnimation, scaleAnimation, nil];
[textLayer addAnimation:animationGroup forKey:@"animateColorAndScale"];
}
aunque sólo habría una manera de establecer una alineación vertical en CATextLayer – bioffe
He aquí una _mucho_ mejor solución utilizando sólo el propio UILabel el original: http: // stackoverflow .com/questions/6442774/is-uilabels-backgroundcolor-not-animatable/6442868 # 6442868 – Anna
@AnnaKarenina El enlace que apuntó es para animar el color de fondo. – xhan