Xamarin Forms:如何将contentPage工具栏图像居中对齐？

<ContentPage.ToolbarItems>
    <ToolbarItem Icon="your_icon_image.png" />
</ContentPage.ToolbarItems>

[assembly: ExportRenderer(typeof(ContentPage), typeof(CustomContentPageRenderer))]
namespace YourApp.Droid
{
    public class CustomContentPageRenderer : PageRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Page> e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null && this.Element.ToolbarItems.Count > 0)
            {
                var toolbar = this.FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar);

                if (toolbar != null)
                {
                    var toolbarItems = ((ContentPage)e.NewElement).ToolbarItems;

                    for (int i = 0; i < toolbarItems.Count; i++)
                    {
                        var toolbarItem = toolbarItems[i];

                        if (!string.IsNullOrEmpty(toolbarItem.Icon))
                        {
                            var drawable = ContextCompat.GetDrawable(Context, toolbarItem.Icon);

                            if (drawable != null)
                            {
                                var toolbarChild = toolbar.GetChildAt(i);
                                if (toolbarChild != null && toolbarChild is ImageButton)
                                {
                                    var imageButton = (ImageButton)toolbarChild;
                                    imageButton.SetImageDrawable(drawable);
                                    imageButton.SetScaleType(ImageView.ScaleType.Center);
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}