android - Calling a method in a Java object from JNI returns error -

i know there many questions asked before, cannot figure out why code not working. have simple class stores string:

public class jnistring {     private string mstring;      public jnistring() {}      public string getstring() {         return mstring;     }      public void setstring(string s) {         mstring = s;     } } 

my jni code (in c), supposed take jnistring object argument, call setstring() function store data, , return integer:

jniexport jint         jnicall java_com_sample_myclass_test(jnienv *env, jobject thiz, jobject jnistring) {     jclass clazz = (*env)->findclass(env, "com/sample/jnistring");     jmethodid methodid = (*env)->getmethodid(env, clazz, "setstring", "(ljava/lang/string;)v");      jstring placeholder = (*env)->newstringutf(env, "placeholder");     (*env)->callvoidmethod(env, clazz, methodid, placeholder);      return 1; } 

and java code:

jnistring jnistring = new jnistring(); // call test() jni function jnistring argument 

but reason, keeps failing following error message:

05-24 23:27:23.099    7575-7575/? a/art﹕ art/runtime/java_vm_ext.cc:410] jni detected error in application: can't call void com.sample.jnistring.setstring(java.lang.string) on instance of java.lang.class<com.sample.jnistring> 05-24 23:27:23.099    7575-7575/? a/art﹕ art/runtime/java_vm_ext.cc:410]     in call callvoidmethod 

i read having call newglobalref() or since ics (i'm running app on kitkat+) on here: http://android-developers.blogspot.ie/2011/11/jni-local-reference-changes-in-ics.html

but can't understand blog post saying, or put in code. appreciated. thanks!

edit: modified jni code following:

jniexport jint             jnicall java_com_sample_myclass_test(jnienv *env, jobject thiz, jobject jnistring) {         jclass clazz = (*env)->getobjectclass(env, jnistring);         jmethodid methodid = (*env)->getmethodid(env, clazz, "setstring", "(ljava/lang/string;)v");          jstring placeholder = (*env)->newstringutf(env, "placeholder");         (*env)->callvoidmethod(env, jnistring, methodid, placeholder);          return 1;     } 

but i'm getting different error:

05-25 19:11:02.832    8802-8802/com.sample e/art﹕ jni error (app bug): attempt use stale local reference 0x1 (should 0x100001) 05-25 19:11:02.850    8802-8802/com.sample a/art﹕ art/runtime/java_vm_ext.cc:410] jni detected error in application: use of deleted local reference 0x1 

you're trying call instance method via class instead of via instance. second parameter needs object instance of jnistring, in case jnistring.