如何在xamarin.android？

Question

我在xamarin android下面遇到异常。我相信它是由proguard引起的，但我无法弄清楚如何保留这个渲染器。

    [ERROR] FATAL UNHANDLED EXCEPTION: System.NotSupportedException: Unable to activate instance of type Com.Syncfusion.Gauges.SfCircularGauge.PointerRenderer from native handle 0xbef9193c (key_handle 0x2eddf05). ---> System.MissingMethodException: No constructor found for 
Com.Syncfusion.Gauges.SfCircularGauge.PointerRenderer::.ctor(System.IntPtr, Android.Runtime.JniHandleOwnership) ---> Java.Interop.JavaLocationException:
 Exception of type 'Java.Interop.JavaLocationException' was thrown.
    11-14 00:16:18.378 E/mono-rt (19328):    --- End of inner exception stack trace ---

我试过以下。我做错了什么或错过了什么？

-keep class com.syncfusion.** { *; }
-keep class * extends com.syncfusion.** { *; }
-keep class Com.Syncfusion.Gauges.SfCircularGauge.PointerRenderer** { *; }  
-keepclassmembers class Com.Syncfusion.Gauges.SfCircularGauge.PointerRenderer** { *; }