JNI Demo

jnidemo.cpp

#include <jni.h>
#include "platform/android/jni/JniHelper.h"
 
void CppToJava(const char* str, bool flag)
{
	cocos2d::JniMethodInfo t;
 
	if (cocos2d::JniHelper::getStaticMethodInfo( t, 
	                                             // package and class name with slashes rather than dots
	                                             "com/my/package/JNIExample",
	                                             // name of java function called
	                                             "JavaFromCpp", 
	                                             // this corresponds to the arguments and return value of the called Java function in reverse.
	                                             // http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/types.html
	                                             "(Ljava/lang/String;[Ljava/lang/String;Z)V")) 
  {
		jstring java_str = 						t.env->NewStringUTF	(str);
		
    // create an array of strings
    jclass jStringCls = t.env->FindClass("java/lang/String");
    jobjectArray str_array = t.env->NewObjectArray( 2, jStringCls, NULL);
      
    jstring keyString1 = t.env->NewStringUTF("one");
    jstring keyString2 = t.env->NewStringUTF("two");
    
    t.env->SetObjectArrayElement(result, 0, keyString1);
    t.env->SetObjectArrayElement(result, 1, keyString2);
		
		t.env->CallStaticVoidMethod		(t.classID, t.methodID, java_str, str_array, (jboolean)flag);
		t.env->DeleteLocalRef					(t.classID);
		t.env->DeleteLocalRef					(java_str);
		t.env->DeleteLocalRef					(str_array);
	}
}
 
extern "C" {
  // The function name here follows a stict naming convention and must be correct in order to recieve call from Java
  // First two arguments are always (JNIEnv* env, jclass clazz) the following are those passed from Java function.
  JNIEXPORT void JNICALL Java_com_my_package_JNIExample_CppFromJava(JNIEnv* env, jclass clazz, jstring str, jfloat num)
  {
    std::string cpp_str = cocos2d::JniHelper::jstring2string(str);
    float cpp_float = (float)jprice;
  }
}