I am trying to implement a custom ImageRenderer in iOS subclassing the native UIImageView, but I am having some problems with CreateNativeControl.
In the older Xamarin.Forms version (like 4.2) the custom native class that I initialized with protected override UIImageView CreateNativeControl() { return new NativeImage(); }
looks like it never get called (the message I log in the constructor is not shown). The Custom Renderer is correctly initialized (the right message is logged).
In the latest stable version (like 4.4) in overriding of CreateNativeControl the return type it is said that has to be a FormsUIImageView, never heard of it, anyway I also tried to subclass that but same problem as before, it seems it never get called as the constructor message is not logged. The Custom Renderer is correctly initialized (the right message is logged).
Here the code I used:
public class IOSImageView : ImageRenderer
{
public IOSImageView()
{
}
protected override void OnElementChanged(ElementChangedEventArgs<Image> e)
{
base.OnElementChanged(e);
if(Control == null)
{
return;
}
Console.WriteLine("PIPPO created from Custom Renderer"); //this message is correctly logged
}
protected override UIImageView CreateNativeControl() //FormsUIImageView in XF 4.4
{
return new NativeImage();
}
}
public class NativeImage : UIImageView //FormsUIImageView in XF 4.4
{
public NativeImage() : base()
{
Console.WriteLine("PIPPO created from native IOS"); //this message is NOT logged
}
public override void TouchesBegan(NSSet touches, UIEvent evt)
{
base.TouchesBegan(touches, evt);
Console.WriteLine("PIPPO touched"); //this (of course because no NativeImage is shown and there is no image to touch) is NOT logged
}
}
FormsUIImageView is new after XF 4.4 which you can check Xamarin.Forms release notes
In your case , you seems want to set the Image Renderer as your custom ImageView, right?
You should invoked SetNativeControl()
protected override void OnElementChanged(ElementChangedEventArgs<Image> e)
{
base.OnElementChanged(e);
if(Control!=null)
{
SetNativeControl(new NativeImage());
}
}
public class NativeImage : FormsUIImageView
{
public NativeImage() : base()
{
this.UserInteractionEnabled = true;
}
public override void TouchesBegan(NSSet touches, UIEvent evt)
{
base.TouchesBegan(touches, evt);
Console.WriteLine("PIPPO touched"); //this (of course because no NativeImage is shown and there is no image to touch) is NOT logged
}
}