(Xamarin) We want to make a .so and dylib framework

Question

We have a .net project (Xamarin) and want to export to a library like .so and dylib, and use it on native iOS and Android application, how to make it?

Answer 1

Hello,

Welcome to our Microsoft Q&A platform!

If you are using Visual Studio, and you are porting to xamarin some JNI-Java code that was already working on Android, follow this Steps:

1.Place your .so files under a lib folder on your Xamarin project, example:

2.Make sure that your .so files are set the Build Action to Android Native Library

3.In C#-Xamarin you can load your libraries in the following way

try  
{  
    JavaSystem.LoadLibrary("SDL2");  
    JavaSystem.LoadLibrary("glib-2.0");  
    JavaSystem.LoadLibrary("gthread-2.0");  
    JavaSystem.LoadLibrary("fluidsynth");  
    JavaSystem.LoadLibrary("sdl_mixer");  
    JavaSystem.LoadLibrary("initmixer");  
}  
catch (UnsatisfiedLinkError e)  
{  
    return e.Message;  
}  

4.the native methods in C# must be declarated in the following way:

[DllImport("initmixer", EntryPoint = "Java_sf2Tools_FluidsynthJNI_loadSong")]  
public static extern int loadSong(IntPtr env, IntPtr thiz, IntPtr songPath, int miliseconds);  
[DllImport("initmixer", EntryPoint = "Java_sf2Tools_FluidsynthJNI_isPlaying")]  
public static extern int isPlaying();  
[DllImport("initmixer", EntryPoint = "Java_sf2Tools_FluidsynthJNI_pauseAudio")]  
public static extern void pauseAudio();  
[DllImport("initmixer", EntryPoint = "Java_sf2Tools_FluidsynthJNI_resumeAudio")]  
public static extern void resumeAudio();  
[DllImport("initmixer", EntryPoint = "Java_sf2Tools_FluidsynthJNI_stopAudio")]  
public static extern void stopAudio();  
[DllImport("initmixer", EntryPoint = "Java_sf2Tools_FluidsynthJNI_setSoundfonts")]  
public static extern void setSoundfonts(IntPtr env, IntPtr thiz, IntPtr js);  

On the "EntryPoint" field you have to put the name of the function exactly as they was in your C/C++ code normally Java_your_package_name_YourClassName_YourMethodName.

For example here is my original C++ code:

void Java_sf2Tools_FluidsynthJNI_setSoundfonts(JNIEnv * env, jobject this, jstring js)  
{  
    //Some code  
}  
void Java_sf2Tools_FluidsynthJNI_pauseAudio(JNIEnv * env, jobject this)  
{  
    //Some code  
}  
void Java_sf2Tools_FluidsynthJNI_resumeAudio(JNIEnv * env, jobject this)  
{  
    //Some code  
}  
int Java_sf2Tools_FluidsynthJNI_isPlaying(JNIEnv * env, jobject this)  
{  
    //Some code  
}  
void Java_sf2Tools_FluidsynthJNI_stopAudio(JNIEnv * env, jobject this)  
{  
    //Some code  
}  

int Java_sf2Tools_FluidsynthJNI_loadSong(JNIEnv * env, jobject this, jstring songPath)  
{  
    //Some code  
}  

Or maybe check the warnings that usually gives Android Studio to know the full name of your native functions:

C/C++

void Java_sf2Tools_FluidsynthJNI_setSoundfonts(JNIEnv * env, jobject this, jstring js)  

C# Xamarin

fluidsynth.setSoundfonts(JNIEnv.Handle, System.IntPtr.Zero, new Java.Lang.String(getCFGPathFiltered()).Handle);  

Refer : https://stackoverflow.com/questions/47433520/load-so-file-in-xamarin-android

And there is similar thead about this, you can check here: https://stackoverflow.com/questions/15896650/xamarin-use-ndk-built-so/15902529#15902529

For dylib , you can check document: https://learn.microsoft.com/en-us/xamarin/ios/platform/native-interop

Best Regards,

Jessie Zhang

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