尝试使用以编程方式创建的图像为UIImageView设置动画时抛出错误

Question

我正在尝试用我以编程方式创建的图像来为UIImageView设置动画。每当我调用startAnimating()时，我都会得到这个错误

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'

我知道当imageView.animationImages中的一个图像为空，而我的图像都不为空时，就会抛出这个错误。

创建一个新的单视图iOS-9应用程序，并将以下代码粘贴到视图控制器的viewDidLoad()中，以查看发生了什么。

    super.viewDidLoad()


    //Create an imageview and add it to the view

    let imageView = UIImageView()

    imageView.translatesAutoresizingMaskIntoConstraints = false

    view.addSubview(imageView)

    imageView.leftAnchor.constraintEqualToAnchor(view.leftAnchor).active = true

    imageView.rightAnchor.constraintEqualToAnchor(view.rightAnchor).active = true

    imageView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor).active = true

    imageView.topAnchor.constraintEqualToAnchor(view.topAnchor).active = true



    //Create an image

    let solidColorFilter = CIFilter(name: "CIConstantColorGenerator")!

    solidColorFilter.setValue(CIColor(color: UIColor.redColor()), forKey: "inputColor")

    let cropFilter = CIFilter(name: "CICrop")!

    cropFilter.setValue(CIVector(CGRect: CGRectMake(0, 0, 300, 300)), forKey: "inputRectangle")

    cropFilter.setValue(solidColorFilter.outputImage, forKey: "inputImage")



    //Create animation images

    var animationImages = [UIImage]()

    let hueAdjustFilter = CIFilter(name: "CIHueAdjust")!

    hueAdjustFilter.setValue(cropFilter.outputImage, forKey: "inputImage")

    for (var i: CGFloat = 0; i < 10; i++) {

        hueAdjustFilter.setValue(-CGFloat(M_PI) + CGFloat(i/10.0) * 2.0 * CGFloat(M_PI), forKey: "inputAngle")

        let hueAdjustedImage = UIImage(CIImage: hueAdjustFilter.outputImage)

        animationImages.append(hueAdjustedImage)

    }


    print("Break here to inspect images in animationImages array. None are nil")


    //Try to animate the images using imageview animationImages

    imageView.animationImages = animationImages

    imageView.animationDuration = 4.0

    imageView.startAnimating() //ERROR THROWN HERE

请帮帮我！谢谢!

Answer 1

我想通了。当从CIImage创建UIImage时，UIImage的CGImage属性为nil。我猜UIImageView的背景层使用CGImage来呈现它自己。无论如何，要从CIImage获取CGImage，我必须创建一个CIContext，然后调用CIContext.createCGImage:FromRect:，然后使用CGImage创建一个UIImage……以下是代码

    //Create a context
    let myEAGLContext = EAGLContext(API: EAGLRenderingAPI.OpenGLES2)

    let options = [kCIContextWorkingColorSpace: NSNull()]

    let myContext = CIContext(EAGLContext: myEAGLContext, options: options)


    //Create animation images

    var animationImages = [UIImage]()

    let hueAdjustFilter = CIFilter(name: "CIHueAdjust")!

    hueAdjustFilter.setValue(cropFilter.outputImage, forKey: "inputImage")

    for (var i: CGFloat = 0; i < 10; i++) {

        hueAdjustFilter.setValue(-CGFloat(M_PI) + CGFloat(i/10.0) * 2.0 * CGFloat(M_PI), forKey: "inputAngle")

        let hueAdjustedCGImage = myContext.createCGImage(hueAdjustFilter.outputImage, fromRect: CGRectMake(0, 0, 300, 300))

        let finalImage = UIImage(CGImage: hueAdjustedCGImage)

        animationImages.append(finalImage)

    }