Question

我正在尝试在更改自定义属性时触发CALayer的动画。当我改变圆的半径时，我希望图层自动触发它的动画。在Objective-C中，可以通过将@dynamic属性设置为属性并覆盖actionForKey:方法来实现（like in this example），这样就可以设置动画。

public class MyCircle : CALayer
{
    [Export ("radius")]
    public float Radius { get; set; }

    public MyCircle ()
    {
        Radius = 200;
        SetNeedsDisplay ();
    }

    [Export ("initWithLayer:")]
    public MyCircle (CALayer other) : base (other) 
    { }

    public override void Clone (CALayer other)
    {
        base.Clone (other);
        MyCircle o = other as MyCircle;
        Radius = o.Radius;
    }

    public CABasicAnimation MakeAnimationForKey (String key)
    {
        CABasicAnimation animation = CABasicAnimation.FromKeyPath (key);
        animation.From = PresentationLayer.ValueForKey (new NSString (key));
        animation.Duration = 1;
        return animation;
    }

    [Export ("actionForKey:")]
    public override NSObject ActionForKey (string key)
    {
        switch (key.ToString ())
        {
            case "radius":
                return MakeAnimationForKey (key);
            default:
                return base.ActionForKey (key);
        }
    }

    [Export ("needsDisplayForKey:")]
    static bool NeedsDisplayForKey (NSString key)
    {
        switch (key.ToString ())
        {
            case "radius":
                return true;
            default:
                return CALayer.NeedsDisplayForKey (key);
        }
    }

    public override void DrawInContext (CGContext ctx)
    {
        // draw circle based in radius
    }
}

但是，在我的C＃/ Monotouch代码中，当值更改时，“radius”永远不会发送到ActionForKey。在上一个问题（Animate a custom property using CoreAnimation in Monotouch?）中，答案和提供的示例代码基于手动调用的自定义属性动画（我不希望这样）。

Monotouch是否支持（由我）所需的行为？我做错了什么？

Answer 1

您在代码中缺少构造函数：

[Export ("initWithLayer:")]
public MyCircle (CALayer other)
    : base (other)
{
}

我不确定它能解决你的问题，但值得一试：）

更改自定义属性时动画CALayer

1 个答案: