Xamarin Forms ToolbarItem icons missed

Good evening!
I have a trouble with android: icons on my toolbaritems not showing up (on iOS everything OK). Toolbar items have just text.

I add toolbar items by this xaml code (c# I have tried, the result is the same):

<views:FeedPageXaml.ToolbarItems>
    <ToolbarItem x:Name="SearchButton" Text="Search" Icon="search.png"/>
</views:FeedPageXaml.ToolbarItems>

In runtime I have warnings:
01-12 17:27:37.554 I/mono-stdout( 9485): Could not load image named: {0}: search.png
[0:] Could not load image named: {0}: search.png

My environment:
- Xamarin Forms 2.0.0.64.90
- icons have png extension (png-20 format)
- icons have BuildAction AndroidResource
- I have done this https://blog.xamarin.com/material-design-for-your-xamarin-forms-android-apps/
- no any errors in Resource.Designer.cs
- my icons are in folders Resources/drawable and Resources/drawable-...

I hope you will help me, because I am fighting with this issue the second day long