Question

我是对UIImageView进行子类化，因此每次设置图像属性时都会发生动画。以下是成功的：

   .card:nth-child(n+1):nth-child(-n+4) {
     @include span(4 of 20);  }
    .card:nth-child(5) {
    @include span(4 of 20 last);  }

这并不奇怪。我将UIImageView子类化并添加了一个名为＆＃39; img＆＃39;的全新变量，后者又修改了UIImageView的图像＆＃39;属性。

问题是最终用户可能会改变AnimatedImageView的图像＆＃39;属性。

import UIKit

class AnimatedImageView: UIImageView {

var img: UIImage! {
    get {
        return self.image
    }
    set {
        self.image = newValue

        UIView.animateWithDuration(0.5, delay: 0.4, usingSpringWithDamping: 0.2, initialSpringVelocity: 5.0, options: .CurveEaseIn, animations: {_ in

            self.transform = CGAffineTransformMakeScale(1.1, 1.1);

            }, completion: {_ in
                self.transform = CGAffineTransformIdentity;
        })
    }
}

这确实会导致堆栈溢出，因为当我调用import UIKit class AnimatedImageView: UIImageView { override var image: UIImage! { get { return self.image } set { self.image = newValue UIView.animateWithDuration(0.5, delay: 0.4, usingSpringWithDamping: 0.2, initialSpringVelocity: 5.0, options: .CurveEaseIn, animations: {_ in self.transform = CGAffineTransformMakeScale(1.1, 1.1); }, completion: {_ in self.transform = CGAffineTransformIdentity; }) } }时，它会反复调用我在子类中重写的setter方法。那么，什么是覆盖＆＃39;图像＆＃39;的getter / setter方法的正确方法。 UIImageView上的属性

Answer 1

只需使用super.image代替，这将阻止循环播放。

Answer 2

使用super.image的另一种方法是通过ivar _image引用图像。它直接引用它，而不调用getter，并避免循环。

import UIKit

class AnimatedImageView: UIImageView {

override var image: UIImage! {
 get {
     return _image
 }
 set {
    _image = newValue

    UIView.animateWithDuration(0.5, delay: 0.4, usingSpringWithDamping: 0.2, initialSpringVelocity: 5.0, options: .CurveEaseIn, animations: {_ in

        self.transform = CGAffineTransformMakeScale(1.1, 1.1);

        }, completion: {_ in
            self.transform = CGAffineTransformIdentity;
    })
 }

覆盖UIImageView的图像getter / setter方法

2 个答案: