[mono-android] Help with .so and java source
goncalo at minkan.net
Sat Feb 18 14:11:11 UTC 2012
Thanks for the reply Jon. It's most likely option 2. I tried the
dllimport route, and I managed to invoke a few methods. Do you believe
this way is better than using jni? I'm just a little rusty with the
linux mangling stuff, that's why I started with jni in the first place.
Sent from my Windows Phone
From: Jonathan Pryor
Sent: 17-02-2012 20:27
To: Discussions related to Mono for Android
Subject: Re: [mono-android] Help with .so and java source
On Feb 17, 2012, at 11:41 AM, Goncalo Oliveira wrote:
> So, here's what I did
> 1. Added the .so library to the project under /NativeLibraries/armeabi/libsdk.so
> 2. Set the library's build action to AndroidNativeLibrary
> 3. Added the java source file under /JavaSources/libmsg.java
> 4. Set the file's build action to AndroidJavaSource
Sanity check: unzip the apk and make sure that lib/armeabi/libsdk.so
is inside the .apk.
> I compile the whole thing, deploy to device and start debugging. When I click the button that calls the LibAPI.HasStarted() I get an Java.Lang.UnsatisfiedLinkError.
Can you provide the full stack trace for the UnsatisfiedLinkError?
I can think of three different reasons for the UnsatisfiedLinkError:
1. The native library is compiled for an architecture that your device
doesn't support. For example, if the .so is an armeabi-v7a library and
you try to load it on an armeabi device, this can fail. I don't think
this is the case here, but it's otherwise possible.
2. The com.alk.sdk.AlkMsg type doesn't have a static constructor which
calls System.loadLibrary("sdk"), and instead requires that "external"
code call System.loadLibrary(). If this is the case, then you should
add a call to Java.Lang.JavaSystem.LoadLibrary("sdk") during your
startup code, sometime before you call AlkMsg.Msg_HasStarted().
3. The native library has been improperly linked, and dlopen() refuses
to load the library. This requires NDK tools to validate.
I would hope that (2) is the problem, and that the
JavaSystem.LoadLibrary() call would fix it.
If (2) doesn't fix it, you could try using the C API that they provide
via P/Invoke and [DllImport]. This would still fail if the problem is
due to (3).
Using a P/Invoke interface would also allow skipping the Java class
and JNIEnv use, so it may be preferable, but without knowing _why_ the
UnsatisfiedLinkError is being thrown, it's difficult to know what the
actual reason is.
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