useobjimpl.cpp

中文JAVA编程思想第二版,一本很好的JAVA入门书籍!

//: appendixb:UseObjImpl.cpp
//# Tested with VC++ & BC++. Include path must 
//# be adjusted to find the JNI headers. See 
//# the makefile for this chapter (in the 
//# downloadable source code) for an example.
#include <jni.h>
extern "C" JNIEXPORT void JNICALL
Java_UseObjects_changeObject(
JNIEnv* env, jobject, jobject obj) {
  jclass cls = env->GetObjectClass(obj);
  jfieldID fid = env->GetFieldID(
    cls, "aValue", "I");
  jmethodID mid = env->GetMethodID(
    cls, "divByTwo", "()V");
  int value = env->GetIntField(obj, fid);
  printf("Native: %d\n", value);
  env->SetIntField(obj, fid, 6);
  env->CallVoidMethod(obj, mid);
  value = env->GetIntField(obj, fid);
  printf("Native: %d\n", value);
} ///:~