Move toolbar items with priority = 0 to LeftBarButtonItems on iOS with Xamarin Forms. Originally written by Murally at http://forums.xamarin.com/discussion/21004/navigation-bar-left-toolbar-button

ExtendedPageRenderer.cs

[assembly: ExportRenderer(typeof(ContentPage), typeof(ExtendedPageRenderer))]

public class ExtendedPageRenderer : PageRenderer
{
    public override void ViewWillAppear(bool animated)
    {
        base.ViewWillAppear(animated);

        var contentPage = this.Element as ContentPage;
        if (contentPage == null || NavigationController == null)
        {
            return;
        }

        var itemsInfo = contentPage.ToolbarItems;

        var navigationItem = this.NavigationController.TopViewController.NavigationItem;
        var leftNativeButtons = (navigationItem.LeftBarButtonItems ?? new UIBarButtonItem[] { }).ToList();
        var rightNativeButtons = (navigationItem.RightBarButtonItems ?? new UIBarButtonItem[] { }).ToList();

        rightNativeButtons.ForEach(nativeItem =>
        {
            // [Hack] Get Xamarin private field "item"
            var field = nativeItem.GetType().GetField("item", BindingFlags.NonPublic | BindingFlags.Instance);
            if (field == null)
            {
                return;
            }

            var info = field.GetValue(nativeItem) as ToolbarItem;
            if (info != null && info.Priority != 0)
            {
                return;
            }

            rightNativeButtons.Remove(nativeItem);
            leftNativeButtons.Add(nativeItem);
        });

        navigationItem.RightBarButtonItems = rightNativeButtons.ToArray();
        navigationItem.LeftBarButtonItems = leftNativeButtons.ToArray();
    }

}

To prevent the Collection Modified Exception, simply do a ToList before the ForEach, like so:

rightNativeButtons.ToList().ForEach(nativeItem =>

This works because now you're iterating over a copy of the list.

Just started using XF-2.2.0* and noticed the private field has been renamed to _item.
So, on line 24 rename "item" to "_item". Then it's working fine again.

And by the way, thanks for this peace of code! It's the best way to move the toolbaritem so far!

How about this such as render for Android ? is possible to Arranged toolbar item to Left even order as secondary ?

@vahidkadivar +1