WatchOS 背景色动画

Question

I'm trying to make a simple animation in WatchKit. I want to blink the specific color, and then come back to black background. It all works fine... once. After this first blink nothing will happen. I've tried searching but couldn't find relevant answer. My guess it that I should somehow reset the state of the animation, but couldn't find any way to do that.

This is the code I'm using for the animation:

animate(withDuration: 0.2, animations: {
    //set first color
    //mainGroup is a WKInterfaceGroup
    self.mainGroup.setBackgroundColor(color)
    //set back black color
    self.mainGroup.setBackgroundColor(UIColor.black)
})

Answer 1

I've researched a bit more. There are no options in animate function in WatchKit, and that is what makes it harder (can't use autoreverse). The solution is not perfect, but it more or less works. You need to first set the desired 'blink' color, and after that animate the transition to black.

self.mainGroup.setBackgroundColor(color)
animate(withDuration: 0.2, animations: {
    self.mainGroup.setBackgroundColor(UIColor.black)
})

Answer 2

If you want a more complicated timing, eg smooth "in" animation, you can use delayed execution:

animate(withDuration: 0.2) {
    self.mainGroup.setBackgroundColor(color)
} 
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.21) {
    animate(withDuration: 0.2) {
        self.mainGroup.setBackgroundColor(.black)
    }
}