UILabel animating number change

Question

I've got an UILabel that displays users score. And score changes from time to time, is there a way to animate this change, to slowly increment this number from its current value to its result value? Something like http://josheinstein.com/blog/index.php/2010/02/silverlight-animated-turbotax-number-display/ but for objective-c.

I found that might be helpful http://stackoverflow.com/questions/3073520/setting-new-text-to-uilabel-and-animation **First look for answer** — wczekalski, Oct 17 '11 at 20:08

Jason Harwig · Accepted Answer · 2011-10-18T18:05:00.830

18

Use a CADisplayLink to change the text property of custom subclass of UILabel over some period of time. You'll probably want to use a NSNumberFormatter for prettier output.

// Create instance variables/properties for: `from`, `to`, and `startTime` (also include the QuartzCore framework in your project)

- (void)animateFrom:(NSNumber *)aFrom toNumber:(NSNumber *)aTo {
    self.from = aFrom; // or from = [aFrom retain] if your not using @properties
    self.to = aTo;     // ditto

    self.text = [from stringValue];

    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(animateNumber:)];

    startTime = CACurrentMediaTime();
    [link addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
}

- (void)animateNumber:(CADisplayLink *)link {
    static float DURATION = 1.0;
    float dt = ([link timestamp] - startTime) / DURATION;
    if (dt >= 1.0) {
        self.text = [to stringValue];
        [link removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
        return;
    }

    float current = ([to floatValue] - [from floatValue]) * dt + [from floatValue];
    self.text = [NSString stringWithFormat:@"%i", (long)current];
}

edited Oct 18 '11 at 18:05

answered Oct 17 '11 at 20:35

Jason Harwig

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Note, if you do use an `NSNumberFormatter`, create one of them and re-use it for every formatting job that uses the same format. Creating a new `NSNumberFormatter` is quite expensive, but re-using an existing one is cheap. – Lily Ballard Oct 17 '11 at 20:50
I keep getting EXC_BAD_ACESS at `float current = ([to floatValue] - [from floatValue]) * dt + [from floatValue]`; – Drabuna Oct 18 '11 at 10:37
are you using properties for the `from` and `to` variables? and is it set to `retain`? If you're not using properties do `from = [aFrom retain]` – Jason Harwig Oct 18 '11 at 18:02
It works great on simulator, but on iphone, it doesn't. It displays 1 number between "from" and "to", and then "to" number. Seems like it lags. Any advice? – Drabuna Oct 21 '11 at 14:59
works great on both simulator and device. awesome Jason. you rock! – JAHelia Mar 17 '12 at 10:37

score 4 · Answer 2 · answered Oct 17 '11 at 20:19

4

AUIAnimatedText has all you was asking for. That is replacement for UILabel with reach text animating possibilities ,

answered Oct 17 '11 at 20:19

wczekalski

720
4
19

UILabel animating number change

2 Answers2

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