小开

Here is the reference:

animations A block object containing the changes to commit to the views. This is where you programmatically change any animatable properties of the views in your view hierarchy. This block takes no parameters and has no return value. This parameter must not be NULL

What I understand about this is when your view call the animation block, then your view label background color is commited to be green since that time. Then, if you don't change the label background color to something else, then it will always be green. This is what I guess

小开

最佳答案

I can't find it documented anywhere, but it appears the backgroundColor property of UILabel is not animatable, as your code works fine with a vanilla UIView. This hack appears to work, however, as long as you don't set the background color of the label view itself:

#import <QuartzCore/QuartzCore.h>


...


theLabel.layer.backgroundColor = [UIColor whiteColor].CGColor;


[UIView animateWithDuration:2.0 animations:^{
theLabel.layer.backgroundColor = [UIColor greenColor].CGColor;
} completion:NULL];

小开

Do the color animation manually, based off of an NSTimer or CADisplayLink callback at some reasonable frame rate (say 20 fps). You will have to calculate your own color change curve in RGB or HSV based on the fractional elapsed time over the full animation time (2.0 seconds in your example), or use an array of 40 intermediate colors.

小开

it says in the docs that backgroundColor is animatable

http://developer.apple.com/library/ios/#documentation/uikit/reference/UIView_Class/UIView/UIView.html#//apple_ref/doc/uid/TP40006816-CH3-SW131

Don't really know since when.

小开

If you don't want to dip down into Quartz, per answer one of the prev answers, create an empty UIView of same size as UILabel and position it in same spot as the UILabel (and in Z order, under it) and you can animate that UIView's background color (I've tried this, and it works for me).

小开

You CAN animate it, but I had to first set it (programmatically) to clearColor for some reason. Without that, the animation either didn't work or wasn't visible.

I am animating the background color of a UILabel in a custom table cell. Here is the code in the willDisplayCell method. I wouldn't try to set the animation in cellForRow, since a lot of the layout gets tinkered with by the table.

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
((RouteListCell *)cell).name.backgroundColor = [UIColor clearColor];
[((RouteListCell *)cell).name backgroundGlowAnimationFromColor:[UIColor whiteColor] toColor:[UIColor redColor] clearAnimationsFirst:YES];
}

Here's my animation routine:

-(void) backgroundGlowAnimationFromColor:(UIColor *)startColor toColor:(UIColor *)destColor clearAnimationsFirst:(BOOL)reset;
{
if (reset)
{
[self.layer removeAllAnimations];
}


CABasicAnimation *anAnimation = [CABasicAnimation animationWithKeyPath:@"backgroundColor"];
anAnimation.duration = 1.00;
anAnimation.repeatCount = HUGE_VAL;
anAnimation.autoreverses = YES;
anAnimation.fromValue = (id) startColor.CGColor; // [NSNumber numberWithFloat:1.0];
anAnimation.toValue = (id) destColor.CGColor; //[NSNumber numberWithFloat:0.10];
[self.layer addAnimation:anAnimation forKey:@"backgroundColor"];
}

小开

Please try this,

[UIView transitionWithView:yourView duration:0.2 options:UIViewAnimationOptionTransitionNone animations:^{


[yourView setBackgroundColor:[UIColor colorWithRed:0.8588 green:0.8588 blue:0.8588 alpha:1]];
}completion:^(BOOL finished) {


}];

It works for me.

小开

I recently came across this problem once again and after some research I figured that basically nothing changed (and probably won't in foreseeable future), so I ended up using Facebook POP framework (not only) for that.

You can easily do animations of basic properties on both view and layer, but in addition, it provides smooth transition between colors (and basically whatever you want, even your custom types, with some additional coding). So for background color, you would do something like this:

   // Create spring animation (there are more types, if you want)
let animation = POPSpringAnimation(propertyNamed: kPOPViewBackgroundColor)


// Configure it properly
animation.autoreverses = false
animation.removedOnCompletion = true
animation.fromValue = UIColor.yourBeginningColor()
animation.toValue = UIColor.yourFinalColor()


// Add new animation to your view - animation key can be whatever you like, serves as reference
label.pop_addAnimation(animation, forKey: "YourAnimationKey")

Viola, now you can animate background colors on everything that has that property!

小开

Swift

(important) Set the UILabel's background color to clear (either in IB or in code). For example:

override func viewDidLoad() {
super.viewDidLoad()


myLabel.backgroundColor = UIColor.clear
}

Animate the layer background color.

@IBAction func animateButtonTapped(sender: UIButton) {


UIView.animate(withDuration: 1.0, animations: {
self.myLabel.layer.backgroundColor = UIColor.red.cgColor
})
}

Note that CGColor is added after the UIColor.

Result

小开

Swift 3

To animate your label background color from white to green, set up your label like this:

self.labelCorrection.backgroundColor = UIColor.clear
self.labelCorrection.layer.backgroundColor = UIColor.white.cgColor

Animate like this:

UIView.animate(withDuration: 2.0) {
self.labelCorrection.layer.backgroundColor = UIColor.green.cgColor
}

To go back to the original state, so you can animate again, make sure you remove animations:

self.labelCorrection.layer.backgroundColor = UIColor.white.cgColor
self.labelCorrection.layer.removeAllAnimations()

小开

Swift 4.1 UILabel Extension:

Add this extension to your code:

extension UILabel {


/** Animates the background color of a UILabel to a new color. */
func animateBackgroundColor(to color : UIColor?, withDuration : TimeInterval, completion : ((Bool) -> Void)? = nil) {
guard let newColor = color else { return }
self.backgroundColor = .clear
UIView.animate(withDuration: withDuration, animations: {
self.layer.backgroundColor = newColor.cgColor
}, completion: completion)
}


}

You should use it like this:

myUILabel.animateBackgroundColor(to: .red, withDuration: 0.5)

Now, if you want to restore the original color, use it like this:

// Storing the orignal color:
let originalColor = myUILabel.backgroundColor


// Changing the background color:
myUILabel.animateBackgroundColor(to: .red, withDuration: 0.5)


// ... Later:


// Restoring the original color:
myUILabel.animateBackgroundColor(to: originalColor, withDuration: 0.5, completion: {
(value: Bool) in
myUILabel.backgroundColor = originalColor
})

How to animate the background color of a UILabel?

Swift