通过JNI从C调用Java方法时，异常NOSUCHMETHODERROR

Question

I have a problem sharing a stream between Java and C with JNI. I am trying to call a Java method from C, but I am getting a nosuchmethodfound exception when I am trying to get GetObjectMethodID .

C Code:

jclass cls = (*env)->GetObjectClass(env, obj);
jmethodID aMethodID = (*env)->GetMethodID(env, cls, "callbackmethod", "(I)V");
if (aMethodID == 0) { 
    log("Unable to get methodID"); //Always getting aMethodID as 0
}
int myvar = 7;
(*env)->CallVoidMethod(env, obj, aMethodID, myvar);

Java Code:

public class myclass extends activity {
    private void callbackmethod(int i) {
        Log.d("Tag", "In Java code");
    }

    -------
    more code
}

Now I am always getting an error Ljava/lang/NoSuchMethodError;: callbackmethod .

Everything looks fine, but my code doesn't work. What is the problem?

Answer 1

Is the JNI method static by any chance? If so, its second parameter is the class, not the this pointer of the current object.

Also, is the method in question in the current class or in its base? Judging by the fact that you spelled activity in all lower case, this is not a copy/paste of your actual code, but a rewrite. It's easier to find errors in real code.

Answer 2

It was my mistake. I was calling the native function from the java static function. I removed the static key word. It's working fine now.