On Mar 20, 2012, at 10:10 AM, Hänke, Maik wrote:
I suspect that the problem is that your native method wants `int lIdentifier`:
> public static native int Msg_UpdateOptions(int lIdentifier, boolean bEnabled,
> boolean bQueue, String functionName, int convention, Object callBackObj);
>
> I import the method with this code:
> public static int Msg_UpdateOptions(uint lIdentifier, bool bEnabled, bool
> bQueue, String functionName, int convention, Java.Lang.Object callBackObj)
Yet you declared the parameter as `uint`. Java doesn't support uint, so when
you construct a JValue around it:
> new JValue(lIdentifier),
it will probably be invoking the JValue(long) constructor, not the JValue(int)
constructor. The result, presumably, is that you're passing a long when an int
is expected, and screwing up the stack.
I would suggest that you instead do:
using (var _functionName = new Java.Lang.String(functionName))
return JNIEnv.CallStaticIntMethod(mAlkClass, methodId, new
JValue[] {
new JValue((int) lIdentifier), // cast uint to
int, so we don't implicitly convert uint to long
new JValue(bEnabled),
new JValue(bQueue),
new JValue(_functionName),
new JValue(convention),
new JValue(callBackObj)
});
The `using` is so that we don't retain a gref for the string longer than
necessary.
> In the Java sample the method is used in this way:
> Msg_UpdateOptions(AlkMsg.MSG_ID_TurnInstructions, true, false,
> "OnTurnInstructionReceived", 0, this );
>
> Where ‚this‘ is an activity and OnTurnInstructionReceived is a method of the
> actvity.
This will be problematic, as what your Java library will have access to is the
generated Android Callable Wrapper, which will not have a declaration for
OnTurnInstructionReceived(). The result is that the method lookup will fail,
presumably resulting in an exception at runtime.
The forthcoming (alpha!) 4.1 release will provide an [Export] custom attribute
to support this scenario. In the meantime, you're probably looking at a painful
world of declaring a Java-side interface and hand-writing a C# binding to that
Java interface. For an example, see:
https://github.com/xamarin/monodroid-samples/blob/master/SanityTests/Adder.java
https://github.com/xamarin/monodroid-samples/blob/master/SanityTests/ManagedAdder.cs
For example, you'd need to add a TurnInstructionReceived.java file to your
project, setting its build action to AndroidJavaSource:
package demo;
public interface TurnInstructionReceived {
void OnTurnInstructionReceived(int buffer, int len);
}
Then add a "fleshed out" version of a C# binding for the above Java interface:
// see
https://github.com/xamarin/monodroid-samples/blob/master/SanityTests/ManagedAdder.cs#L82
[Register("demo/TurnInstructionReceived", DoNotGenerateAcw=true)]
interface ITurnInstructionReceived : Android.Runtime.IJavaObject {
// Note: TODO_AQN is the AssemblyQualifiedName of the assembly
containing this type.
[Register ("OnTurnInstructionReceived", "(II)V",
"GetOnTurnInstructionReceivedHandler: ITurnInstructionReceivedInvoker,
TODO_AQN")]
void OnTurnInstructionReceived(int buffer, int len);
}
class ITurnInstructionReceivedInvoker : Java.Lang.Object,
ITurnInstructionReceived {
// ...lots of stuff omitted...
static Delegate cb_OnTurnInstructionReceived;
static Delegate GetOnTurnInstructionReceivedHandler ()
{
if (cb_OnTurnInstructionReceived == null)
cb_OnTurnInstructionReceived =
JNINativeWrapper.CreateDelegate((Action<IntPtr, IntPtr, int, int>)
n_OnTurnInstructionReceived);
return cb_OnTurnInstructionReceived;
}
static void n_OnTurnInstructionReceived(IntPtr jnienv, IntPtr
lrefThis, int buffer, int len)
{
ITurnInstructionReceived __this =
Java.Lang.Object.GetObject<ITurnInstructionReceived >(lrefThis,
JniHandleOwnership.DoNotTransfer);
__this.OnTurnInstructionReceived(buffer, len);
}
}
With the above two files, you could then modify your activity to implement
ITurnInstructionReceived, allowing Msg_UpdateOptions() to invoke the
OnTurnInstructionReceived() method.
- Jon
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