Android JNI method - Is the second parameter jclass or jobject?

Question

Folks,

In my Android Java code, I have a declaration as follows:

public class SurfacePanelNative extends SurfaceView implements SurfaceHolder.Callback {
   ...
   private static native void native_render();
}

In my native code, I have the function declared as:

void native_render(JNIEnv *env, jobject javaSurface) {
   ANativeWindow* window = ANativeWindow_fromSurface(env, javaSurface);
   ...
}

Looking at some examples on the net, it appears that the function should be declared as:

void native_render(JNIEnv *env, jclass clazz) {
   ...
}

I am wondering which declaration is the right one.

I am thinking the first one is the right one. Otherwise, I don't have enough information to obtain javaSurface.

I would appreciate it if someone can shed some light on this.

Thank you in advance for your help.

Regards,
Peter

Answer 1

It is jclass if the method is static, otherwise jobject. If you use javah, as the JNI designers intended, you will always get the right answer.