Xamarin Forms iOS Renderer - ToolBar Standard Icons - ios

Question

I can create a simple Tab Renderer which will update my Forms ToolBarItems to use the built in iOS icons like below.
NavigationController is only NOT NULL in ViewWillAppear If I try it in ViewDidLoad, it is NULL.
The problem with this is you get a flash of the TabBar Item text before it gets replaced with the actual icon.
Is there a different place I should be intercepting the ToolBar behavior?
[assembly: ExportRenderer(typeof(TabbedPage), typeof(TabRenderer))]
namespace Cellar.iOS.Renders
{
public class TabRenderer : TabbedRenderer
{
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
var list = new List<UIBarButtonItem>();
foreach (var item in NavigationController.TopViewController.NavigationItem.RightBarButtonItems)
{
if (string.IsNullOrEmpty(item.Title))
{
continue;
}
if (item.Title.ToLower() == "add")
{
var newItem = new UIBarButtonItem(UIBarButtonSystemItem.Add)
{
Action = item.Action,
Target = item.Target
};
list.Add(newItem);
}
if (list.Count > 0)
NavigationController.TopViewController.NavigationItem.RightBarButtonItems = list.ToArray();
}
}
}
}

Answer 1

override OnElementChanged method:
protected override void OnElementChanged(VisualElementChangedEventArgs e)
{
base.OnElementChanged(e);
if(e.NewElement!= null)
{
var list = new List<UIBarButtonItem>();
// Your code goes here
}
}

Answer 2

Yes, you should override the PushViewController and inherit from NavigationRenderer method. Here is what I am using in my application:
public class CustomToolbarRenderer : NavigationRenderer
{
public override void PushViewController(UIViewController viewController, bool animated)
{
base.PushViewController(viewController, animated);
List<UIBarButtonItem> newItems = new List<UIBarButtonItem>();
foreach (UIBarButtonItem i in TopViewController.NavigationItem.RightBarButtonItems)
{
if (i.Title != null)
{
if (i.Title.Equals(Constants.Toolbar.Add))
{
var newItem = new UIBarButtonItem(UIBarButtonSystemItem.Add);
newItem.Action = i.Action;
newItem.Target = i.Target;
newItems.Add(newItem);
}
else if (i.Title.Equals(Constants.Toolbar.Camera))
{
var newItem = new UIBarButtonItem(UIBarButtonSystemItem.Camera);
newItem.Action = i.Action;
newItem.Target = i.Target;
newItems.Add(newItem);
}
else if (i.Title.Equals(Constants.Toolbar.Delete))
{
var newItem = new UIBarButtonItem(UIBarButtonSystemItem.Trash);
newItem.Action = i.Action;
newItem.Target = i.Target;
newItems.Add(newItem);
}
else
newItems.Add(i);
}
else
newItems.Add(i);
}
TopViewController.NavigationItem.RightBarButtonItems = newItems.ToArray();
}
}

Answer 3

Try the below code at the end or after the execution of the required code block...
return base.ViewWillAppear(animated);