动画化CALayer子类的自定义属性 [英] Animating a custom property of CALayer subclass

问题描述

我有一个CALayer子类MyLayer，它有一个名为myInt的NSInteger属性。我真的想通过CABasicAnimation为这个属性设置动画，但似乎CABasicAnimation只适用于所谓的动画属性（边界，位置等）。有什么我可以覆盖以使我的自定义myInt属性可动画吗？

I have a CALayer subclass, MyLayer, that has a NSInteger property called myInt. I'd really like to animate this property via CABasicAnimation, but it seems CABasicAnimation only works on so-called "animatable" properties (bounds, position, etc). Is there something I can override to make my custom myInt property animatable?

推荐答案

是的，它是可能的（仅在最新的Core动画中）我相信，即iPhone 3.0+和OS X 10.6 +版本。

Yes, it's possible (only in the latest Core Animation releases though, I believe, i.e. iPhone 3.0+ and OS X 10.6+).

1. 让你的财产动态，以便CA实现你的访问者：

1. Make your property dynamic so that CA implements the accessors for you:

@dynamic myInt;

告诉图层属性的更改需要重绘：

Tell the layer that changes of the property require redrawing:

+ (BOOL)needsDisplayForKey:(NSString*)key {
    if ([key isEqualToString:@"myInt"]) {
        return YES;
    } else {
        return [super needsDisplayForKey:key];
    }
}

使用<$ c $的值c> myInt 在 drawInContext：方法中。现在，当您为 myInt 设置动画时，Core Animation将为动画的每个步骤插值，并反复让图层自行绘制。

Use the value of myInt in your drawInContext: method. Now, when you animate myInt, Core Animation will interpolate the values for each step of the animation and repeatedly ask the layer to draw itself.

如果您还想为此属性启用隐式动画，还要覆盖 actionForKey：。

If you also want to enable implicit animations for this property, also override actionForKey:.

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