android - geting no result from GetStringUTFChars JNI -

android ndk android application. stuck on starting lines , not compiling further. following code. doest not compile after "str = (*env)->getstringutfchars(env, filename, null);". please check java , c code

the java code:

public class myffmpegactivity extends activity {  private static native int logfileinfo(string filename);  static {     log.i("heha", "hoha");     system.loadlibrary("mylib"); }  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_myffmpeg);     string path=environment.getexternalstoragedirectory().getpath();     path=path+"/test.mp4";     log.i("name returned ", ":"+path); int x=logfileinfo(path);   } 

the c code

jint java_com_example_myffmpegtest_myffmpegactivity_logfileinfo(jnienv * env, jobject  this, jstring filename) {  av_register_all();    avformatcontext *pformatctx;    const jbyte *str;    str = (*env)->getstringutfchars(env, filename, null);  if(av_open_input_file(&pformatctx, str, null, 0, null)!=0)  {     loge("can't open file '%s'\n", str);     return 1; } else {      logi("file opened\n");     logi("file '%s', codec %s",         pformatctx->filename,         pformatctx->iformat->name     ); } return 0;} 

here correct syntax:

const char *str; str = (*env)->getstringutfchars(env, filename, null); 

also, looks trying develop created solution for. check out ffmpegmediametadataretriever.