AndroidJavaObject / JNI with float arrays

I have a particular piece of Android JNI code that I just can't get to work.

Code (CSharp):

1.     public float[] getOrientation()
2.     {
3.         const int matrix_size = 16;
4.         float[] R = new float[matrix_size];
5.         float[] I = new float[matrix_size];
6.         float[] values = new float[3];
7.  
8.         if (map[Sensor.Type.Accelerometer].sensor != null && map[Sensor.Type.MagneticField].sensor != null)
9.         {
10.             SensorManager.getRotationMatrix(R, I, map.get(Sensor.TYPE_ACCELEROMETER).values, map.get(Sensor.TYPE_MAGNETIC_FIELD).values);
11.             SensorManager.getOrientation(R, values);
12.         }
13.  
14.         return values;
15.     }

The part about the map / sensor stuff is easy and works, but I can't get the in/out array creation to work. The main issue is that I don't seem to be able to construct AndroidJavaObjects that hold R, I and "values". There's a constructor for AndroidJavaObject that sounded promising

Code (CSharp):

1. _R = new AndroidJavaObject(new object[] { R });

, but only exists in the Editor (??) and throws a compiler error saying the signature should be (string, params object[]).

What's the right way to create those arrays and pass them into the function? Do I have to resort to raw JNI methods for calling it with IntPtr arguments?

 

I have done this to pass Color32[] blobs over to a native plugin, basically pinning the object and passing it over. This approach works well with iOS, Android (the C code was JNI-compiled into an AAR), MacOSX and Win32, all same-same on the C# side (except for subtle naming differences in the DLLImport decorator of the extern declarations).

Here is the codelets I used, first the calling site:

Code (csharp):

1.     public static void PinTextureAndCallNativeRenderColor( Texture2D t2d, int span, bool clean = false)
2.     {
3.         if (clean || (pixels == null) || (span != pixelSpan))
4.         {
5.             pixelSpan = span;
6.             pixels = new Color32[ pixelSpan * pixelSpan];
7.         }
8.  
9.         GCHandle handle = GCHandle.Alloc(pixels, GCHandleType.Pinned);
10.         try
11.         {
12.             dispatcher1_rendercolor( handle.AddrOfPinnedObject(), span, 0);
13.         }
14.         finally
15.         {
16.             if (handle.IsAllocated)
17.             {
18.                 handle.Free ();
19.             }
20.         }
21.      
22.         t2d.SetPixels32( pixels);
23.         t2d.Apply();
24.     }

And then the C# interop declaration was:

Code (csharp):

1.     [DllImport ("vanilib")]
2.     private static extern void dispatcher1_rendercolor ( System.IntPtr pixels, int span, int flags);