an example code of GetMethodID
Gabriel Huie
function in java being called from C. I looked up some examples online
but when I'm doing it my GetMethodID is returning 0 so i guess it
can't find the method I was hoping someone had an example using the
Android stuff in Eclipse maybe Im just not including a path or
something simple like that but just wondering if anyone has a simple
example so i can compare and see if im missing a step.
Onur Cinar
The signature should match, so that might be the issue. You may need
to use javap on command line:
javap -s -private com.my.Object
This should print the signatures for the methods in your class. After
you have the right signature, in JNI you can do the following:
jclass clazz = env->GetObjectClass(obj);
jmethodID myMethod = env->GetMethodID(clazz, "myMethod", "(III)V");
This should return a valid method id. If it doesn't, then could you
copy/paste the portion of your code, so we can troubleshoot?
Regards,
-onur
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Gabriel Huie
basically because I dont get how to use javap. I did what u said wtih
javap-s -private com.my.object
but basicaly it keeps saying it cant find that package or class
Where in the directory do u do for the eclipse like i really cant
figure this out
Onur Cinar
Hi Gabriel,
You need to run javap at the root level of your class files directory (the bin directory on Eclipse I believe). Or you can use the -classpath argument to specify the classpath.
Regards,
-onur
Gabriel Huie
in eclipse
public void callbacks(){
song_label.setText("jni");
}
this is the java code
then
this is my jni code
jstring
Java_com_bfrx_Bfrx_SSHDPlayFile( JNIEnv* env, jobject thiz, jstring
str){
char *nativeStr = (char*)env->GetStringUTFChars(str, 0);
jclass cls = env->GetObjectClass(thiz);
jmethodID mid = env->GetMethodID( cls, "callbacks", "()V");
//printf("%d the mid \n", cls);
env->CallVoidMethod( thiz, mid);
//printf("%s here in jni first \n", nativeStr);
//fclose (stdout);
return str;
}
the signature and method name is correct after doing the javap thing
soo the only thing i could think would be a reason for it not working
is maybe i need to do like
"Java_com_bfrx_Bfrx_callbacks"
I mean iono cuz i stll get a 0 in mid
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Igor R
> in eclipse
> public void callbacks(){
> song_label.setText("jni");
> }
> this is the java code
>
> then
> this is my jni code
> jstring
> Java_com_bfrx_Bfrx_SSHDPlayFile( JNIEnv* env, jobject thiz, jstring
> str){
> char *nativeStr = (char*)env->GetStringUTFChars(str, 0);
> jclass cls = env->GetObjectClass(thiz);
> jmethodID mid = env->GetMethodID( cls, "callbacks", "()V");
> //printf("%d the mid \n", cls);
>
> env->CallVoidMethod( thiz, mid);
> //printf("%s here in jni first \n", nativeStr);
> //fclose (stdout);
> return str;
> }
>
> the signature and method name is correct after doing the javap thing
> soo the only thing i could think would be a reason for it not working
> is maybe i need to do like
> "Java_com_bfrx_Bfrx_callbacks"
> I mean iono cuz i stll get a 0 in mid
The GetMethodID parameters seem to be correct, but are you sure you
get the correct class with GetObjectClass? What do you see in logcat
output, does it say something when you call
GetObjectClass/GetMethodID?