how get jni acces?

[MatejMagat305]

well I try to open my copy libOpenCL.so in apk (systems libs reject access) and I need location of ..., I try

//go:build android

package openCL

/*
#include <jni.h>
#include <stdlib.h>
#include <string.h>

extern struct android_app *GetAndroidApp();
const char* GetNativeLibraryDir() {
    const char* result = NULL;
    struct android_app* app = GetAndroidApp();
    if (!app) {
        goto cleanup;
    }
    JNIEnv* env = app->activity->env;
    jclass contextClass = (*env)->GetObjectClass(env, app->activity->clazz);
    if (!contextClass) {
        goto cleanup;
    }
    jmethodID getApplicationContextMethod = (*env)->GetMethodID(
        env, contextClass, "getApplicationContext", "()Landroid/content/Context;");
    if (!getApplicationContextMethod) {
        goto cleanup;
    }
    jobject contextObject = (*env)->CallObjectMethod(env, app->activity->clazz, getApplicationContextMethod);
    if (!contextObject) {
        goto cleanup;
    }
    jmethodID getApplicationInfoMethod = (*env)->GetMethodID(
        env, contextClass, "getApplicationInfo", "()Landroid/content/pm/ApplicationInfo;");
    if (!getApplicationInfoMethod) {
        goto cleanup;
    }
    jobject applicationInfoObject = (*env)->CallObjectMethod(
        env, contextObject, getApplicationInfoMethod);
    if (!applicationInfoObject) {
        goto cleanup;
    }
    jfieldID nativeLibraryDirField = (*env)->GetFieldID(
        env, (*env)->GetObjectClass(env, applicationInfoObject),
        "nativeLibraryDir", "Ljava/lang/String;");
    if (!nativeLibraryDirField) {
        goto cleanup;
    }
    jstring nativeLibraryDirString = (*env)->GetObjectField(
        env, applicationInfoObject, nativeLibraryDirField);
    if (!nativeLibraryDirString) {
        goto cleanup;
    }
    const char* nativeLibraryDir = (*env)->GetStringUTFChars(env, nativeLibraryDirString, NULL);
    if (!nativeLibraryDir) {
        goto cleanup;
    }
    result = strdup(nativeLibraryDir);
    (*env)->ReleaseStringUTFChars(env, nativeLibraryDirString, nativeLibraryDir);

cleanup:
    if (contextClass) (*env)->DeleteLocalRef(env, contextClass);
    if (contextObject) (*env)->DeleteLocalRef(env, contextObject);
    if (applicationInfoObject) (*env)->DeleteLocalRef(env, applicationInfoObject);
    if (nativeLibraryDirString) (*env)->DeleteLocalRef(env, nativeLibraryDirString);
    return result;
}
*/
import "C"
import (
	"unsafe"
        ".../purego"
)

func init() {
	cStr := C.GetNativeLibraryDir()
	if uintptr(cStr) != uintptr(0) {
		dir := C.GOString(cStr)
		C.free(unsafe.Pointer(cStr))
		purego.Dlopen(dir+"/libOpenCL")
	}
}

but I have no luck...

please give me advise

[gen2brain]

No idea, but it is not related in any way to raylib, sorry. This is not the best place for questions and discussions, it is for issues with raylib-go.

[gen2brain]

Why even try to use something like purego on Android, how is it going to find the library there? Does it even support Android? You anyway need C for shared library so why not just use C?

[gen2brain]

I just looked at this, and still am not sure what you are trying to do here. JNI is used to access Java from C, of C from Java, you don't even have Java here. You just should use C, i.e. include headers you need, call what you want, and link with that library. How is JNI even related to this?

[MatejMagat305]

well, sometime I need jni to call something extra ...,

I was able to run my OpenCL purego wrapper on termux(android enviroment), so I would like to try in apk ...

So my question is whether is android_app *GetAndroidApp(); available outside internal library

[gen2brain]

You can see for yourself that it is not exposed.
So how is your example related to JNI then? I still don't understand why you even go with all that trouble with purego, just use cgo, link the library, and put the library in android/libs, what do jni and purego have to do with that? There is nothing to gain here, you must use C anyway.

[MatejMagat305]

so, purego is primary to avoid cgo, but it is also good to avoid complicate link with headers ..., so if I (in my wrapper) create var somename func(...); porego.RegisterFunc(handle, "...", &somename) I do not have to write other version for cgo version, it will work even in cgo (yes, if you have cgo which has good link, it is useless, because cgo is litle bit faster, but if c headers in f.e. in android is coplicate purego still can be usefull)

[gen2brain]

But you cannot avoid cgo if you want to compile library as c-shared. You must use it on Android no matter what else you are doing, so how do you avoid cgo?

[gen2brain]

In my experience, purego and cgo have exactly the same performance (i.e. I use it for some image decoders). And if I already must use cgo, I just really don't see a point to use experimental library that doesn't even work if function receives or returns a plain struct.

[MatejMagat305]

well, I was found

raylib-go/raylib/utils_android.go

Line 37 in c3665eb

func HomeDir() string {

I am NOT trying avoid cgo in android, compile headers to android in Go is hard, so I was try use purego as "cheap wrapper" with many options of paths (androids are very variable with path shared lib) as I have in https://github.com/opencl-pure/pureCL/blob/9bd3c662ac677f6f25beb12282d1e267b5babade/purego_library_unix.go#L25
similar to https://github.com/krrishnarraj/libopencl-stub/blob/4a235674884fcb75886142dd4ce2f9aa08117037/src/libopencl.c#L82 ...

as I notice android libOpenCL.so is not public ..., so I was try copy to internal lib ...