Not sure (didn't actually try), but the only wrong thing I've noticed is the return type of your method declarations.
Java-side
public native int getString()
NDK-side
JNIEXPORT jstring JNICALL Java_app_cloudstringers_Completed_getString(JNIEnv* env, jobject thiz)
In Java, you have an int
. On the C-side, you have a jstring
.