In earlier versions an android XML drawables can be used as toolbar icons.
For example: https://bugzilla.xamarin.com/show_bug.cgi?id=25661#c12
Please note - there is no other way to show different icons for enabled/disabled toolbar items.
In 2.3.4, after merging https://github.com/xamarin/Xamarin.Forms/pull/437, this functionality was broken - now only PNG files can be used. Attempt to use XML drawables causes errors in android log like this:
E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException: /ic_delete_white: open failed: ENOENT (No such file or directory)
And corresponded toolbar item contains text only.
Please, restore possibility to use XML drawables in XF.Android.
Should be fixed in 2.3.4-pre6. Thank you!