Animate a custom property using CoreAnimation in Monotouch? - iphone

Question

This is essentially the same question as posted here: Animating a custom property in a CALayer
over a year ago and hasn't been answered.
Im creating a custom layer and drawing a circle on it. I'd like to be able to animate the radius of the circle (and other properties later). From what i've read, i've set it up like so:
public class CircleLayer : CALayer
{
//[Export("radius")]
//public float Radius { get;set; }
//EDIT: I've now changed the radius field to what is coded below
public float Radius;
[Export("radius")]
public float getRadius()
{
return Radius;
}
[Export("setRadius:")]
public void setRadius(float val)
{
Radius = val;
}
public float Thickness {get;set;}
public CGColor Color {get;set;}
public float GlowAmount {get;set;}
private SizeF GlowOffset {get;set;}
[Export ("needsDisplayForKey:")]
static bool NeedsDisplayForKey (NSString key)
{
Console.WriteLine(key.ToString());
if(key.Equals("radius"))
{
return true;
}
else
return false;
}
public CircleLayer ()
{
if(GlowAmount == 0.0f)
GlowAmount = 10f;
GlowOffset = new SizeF(0f,0f);
//CALayer.NeedsDisplayForKey("radius");
}
public override void DrawInContext (CGContext context)
{
base.DrawInContext (context);
Console.WriteLine("drawing...........");
PointF centerPoint = new PointF(125,125);//this.Frame.Width/2,this.Frame.Height/2);
//Outer circle
context.AddEllipseInRect(new RectangleF(centerPoint.X - Radius,
centerPoint.Y - Radius,
Radius * 2,
Radius * 2));
//Inner circle
context.AddEllipseInRect(new RectangleF(centerPoint.X - InnerRadius,
centerPoint.Y - InnerRadius,
InnerRadius * 2,
InnerRadius * 2));
//Fill in circle
context.SetFillColor(Color);
context.SetShadowWithColor(GlowOffset,GlowAmount,GlowColor);
context.EOFillPath();
}
}
But it just doesn't work. I never get the radius key reported when NeedsDisplayForKey gets called (and prints them to the console). I can animate standard properties no problem (eg: scale)
Edit: Note that I can now successfully modify the value of the property Radius using SetValueForKey. If I do this I need to call SetNeedsDisplay() to update the screen, however i still cannot get the animation to work at all.
Edit #2: Sample attached: http://dl.dropbox.com/u/8617393/GraphicsTest1.zip

Answer 1

This has unfortunately been impossible to do with MonoTouch - but we've fixed it for the next beta (5.3.3) which will hopefully be released soon.
Once 5.3.3 has been released you can use this sample: https://github.com/xamarin/monotouch-samples/tree/monotouch-5.4/CustomPropertyAnimation to see how to do it.