C/C++和Java的交互详解

package com.example.testjni;

public class TextJni {
  // support to c
  static {
    System.loadLibrary("jniinterface");
  }
  public static native int getInt();
  public static native String getString();
}

  javah com.example.testjni.TextJni
  # 注意如果要有Android SDK的类需要指定classpath, 如
  javah -classpath /Users/Richard/dev/android/sdk/platforms/android-19/android.jar:./bin/classes com.togic.gameengine.GFRenderer

com_example_testjni_TextJni.cpp:

#include <stdio.h>
#include <stdlib.h>
#include "com_example_testjni_TextJni.h"

int sum ()
{
  int x,y;
  x = 100 ;
  y = 1000;
  x += y;
  return x;
}

//实现 com_example_textjni_textJNI.h 的方法
JNIEXPORT jint JNICALL Java_com_example_testjni_TextJni_getInt(JNIEnv * env, jclass cls)
{
  return sum();
}

JNIEXPORT jstring JNICALL Java_com_example_testjni_TextJni_getString(JNIEnv * env, jclass cls)
{
  return env->NewStringUTF("HelloNDK!");
}

Android.mk:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE := jniinterface
LOCAL_SRC_FILES := com_example_testjni_TextJni.cpp

#LOCAL_C_INCLUDES := $(LOCAL_PATH)
include $(BUILD_SHARED_LIBRARY)

JNIEXPORT jstring JNICALL Java_com_togic_testjni2_TextJni_getString(JNIEnv * env, jclass cls)
{
  jclass TextJni;
  jobject instTextJni;
  jmethodID getCurrInt;

  JNIEnv* jniEnv = env;

  TextJni = jniEnv->FindClass("com/togic/testjni2/TextJni");

  jmethodID construction_id = jniEnv->GetMethodID(TextJni, "init", "()V");
  instTextJni = jniEnv->NewObject(TextJni, construction_id);

  getCurrInt = jniEnv->GetStaticMethodID(TextJni, "getCurrInt","()I");

  // call java static method
  jint jiref = jniEnv->CallStaticIntMethod(TextJni, getCurrInt);

  // clean
  jniEnv->DeleteLocalRef(TextJni);
  jniEnv->DeleteLocalRef(instTextJni);

  std::string strRef = "HelloNDK!" + view->getStaticString();
  return env->NewStringUTF(strRef.c_str());
}

jclass clazz = env->FindClass(classname);

jclass clazz = (*env)->FindClass(env, classname);