iOS 11 animated gif display in UIImageView

问题

I thought iOS 11 was supposed to bring, at long last, native support for animated gifs? But I tried this, and I didn't see any animation:

let im = UIImage(named:"wireframe.gif")!
let iv = UIImageView(image:im)
iv.animationImages = [im] // didn't help
iv.frame.origin = CGPoint(0,100)
iv.frame.size = im.size
self.view.addSubview(iv)
delay(2) {
    iv.startAnimating() // nope
}

How is this supposed to work?

回答1:

iOS 11 does bring a native understanding of animated gifs, but that understanding, infuriatingly, is not built into UIImageView. It is still up to you to translate the animated gif into a sequence of UIImages. Apple now provides sample code, in terms of the ImageIO framework:

https://developer.apple.com/library/content/samplecode/UsingPhotosFramework/Listings/Shared_AnimatedImage_swift.html

That code implements an AnimatedImage class, which is essentially a collection of CGImages extracted from the original animated gif. Thus, using that class, we can display and animate the animated gif in a UIImageView as follows:

let url = Bundle.main.url(forResource: "wireframe", withExtension: "gif")!
let anim = AnimatedImage(url: url)!
var arr = [CGImage]()
for ix in 0..<anim.frameCount {
    arr.append(anim.imageAtIndex(index: ix)!)
}
var arr2 = arr.map {UIImage(cgImage:$0)}
let iv = UIImageView()
iv.animationImages = arr2
iv.animationDuration = anim.duration
iv.frame.origin = CGPoint(0,100)
iv.frame.size = arr2[0].size
self.view.addSubview(iv)
delay(2) {
    iv.startAnimating()
}

回答2:

Unfortunately, the inter-frame timing of a GIF can vary between frames, so answers that use ImageIO to load the frames and then set them as the animatedImages on a UIImageView need to properly extract the timings and take them into account.

I recommend Flipboard's FLAnimatedImage, which handles GIFs correctly. https://github.com/Flipboard/FLAnimatedImage.

来源：https://stackoverflow.com/questions/45745432/ios-11-animated-gif-display-in-uiimageview