How to animate incrementing number in UILabel in swift
I have a label showing a number and I want to change it to a higher number, however, I'd like to add a bit of flare to it. I'd like to have the number increment up to the higher number with an ease-in-out curve so it speeds up then slows down. Please, how to implement this in swift, Here is my code. Thanks.
let newValue : Double = 1000
let oldValue : Double = 500
timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: Selector("countAnimation:"), userInfo: ["oldValue":oldValue, "newValue": newValue], repeats: true)
func countAnimation(timer: NSTimer)
{
let dict = timer.userInfo as? [String:AnyObject]
var OldTotalValue : Double = (dict!["oldValue"] as? Double)!
let newTotalValue : Double = (dict!["newValue"] as? Double)!
OldTotalValue = OldTotalValue + 10
if newTotalValue < OldTotalValue
{
timer.invalidate()
}
else
{
mylabel.text = String(OldTotalValue)
}
}
I am not entirely familiar with swift. But I have implemented this previously using a parabolic curve.
In detail more or less what is happening is basic algebra. You have a graph with a value x on one axis and then y in the time axis. You want the time delay between each animation to increase until it reaches a plateau.
For example:
x=1 delay= 100ms, x=2 delay =200ms, x=3 delay=310ms, x=4 delay=430ms
notice that every increase is more than the previous.
Mathematically to get such a slope, you could sit in front of a formula such as:
y = -x + x^2
and play around with it until you get an output such that for every increment of x your delay corresponds to a nice slow down that will look clean on an animation.
Thankfully Apple as included libraries that will do this, I found it with a quick search:
UIViewAnimationOptions.CurveEaseOut
This library will give you a curve that starts quickly then slows down, here is the rest of the Apple Documentation
请检查这一点：
func countAnimation(timer: NSTimer)
{
UIView.transitionWithView(label,
duration: 1.0,
options: [.CurveEaseInOut],
animations: { () -> Void in
// Write your code here
}, completion: nil)
}