How to use JNI registerNatives inside c++ class?

I have a c++ class called androidGPS with public methods and variables. Inside this class I am using JNI to calls some java code. But I am stuck in the registerNatives function.

My c++ class has this void method:

void LocationChanged(JNIEnv* env, jobject object, jstring paramsString);

Implemented in this way:

void androidGPS::LocationChanged(JNIEnv*, jobject, jstring paramsString)
{
    const char * nativeString = currEnv->GetStringUTFChars(paramsString, 0);

    QString qstring(nativeString);
    QStringList res;
    res << qstring;
    emit newReadAvailable(res);
}

The Java class that I try to link to has the following method:

public static native void sndonLocationChanged(String currLocation);

I am declaring the JNINativeMethods as a local variable before calling the register natives like:

JNINativeMethod methods[] =
{
    {
         "sndonLocationChanged",
         "(Ljava/lang/String;)V",
         (void *)&androidGPS::LocationChanged
    }
};

The register natives call is this:

int numMethods;
    numMethods = sizeof(methods) / sizeof(methods[0]);
    if (currEnv->RegisterNatives(listenerClass, methods, numMethods) < 0)
    {
        if (currEnv->ExceptionOccurred())
        {
            classError = true;
            emit error("JNI--Error running RegisterNatives");
            stopGPSService();
            return false; //Return with error
        }
        else
        {
            emit error("JNI--Error running RegisterNatives");
            stopGPSService();
            return false; //Return with error
        }
    }

The compiler gives 开发者_如何学Cme the warning:

warning: converting from 'void (androidGPS::)(JNIEnv, _jobject*, _jstring*)' to 'void*'

The c++ application crashes when I call the function sndonLocationChanged() in the class through JNI. I cannot see the error in the c++, but the Dalvik does not generate an error.

I guess is because I am not calling properly registerNatives or not declaring properly the methods (hence the warning).

If I declare LocationChanged static as:

static jboolean LocationChanged(JNIEnv* env, jobject object, jstring paramsString);

It does not fail but I cannot pass paramsString into class members!

Any idea how can I fix this?

Many thanks,

Carlos.

One option is that you give your Java code a means of getting a pointer to your native androidGPS object and passing it down to the non-class-function LocationChanged(), and it calls androidGPS::LocationChanged().

Callbacks into non-static C++ objects are problematic and typically are solved using a static helper function coupled with either a pointer to the object that the callback should be invoked on, or use of a static pointer to a singleton object.