pdk/ndk/samples/samplejni/native.cpp

#include <jni.h>
#include <stdio.h>

static jint
add(JNIEnv *env, jobject thiz, jint a, jint b) {
int result = a + b;
    printf("%d + %d = %d", a, b, result);
    return result;
}

static const char *classPathName = "com/example/jniexample/Native";

static JNINativeMethod methods[] = {
  {"add", "(II)I", (void*)add },
};

/*
 * Register several native methods for one class.
 */
static int registerNativeMethods(JNIEnv* env, const char* className,
    JNINativeMethod* gMethods, int numMethods)
{
    jclass clazz;

    clazz = env->FindClass(className);
    if (clazz == NULL) {
        fprintf(stderr, "Native registration unable to find class '%s'", className);
        return JNI_FALSE;
    }
    if (env->RegisterNatives(clazz, gMethods, numMethods) < 0) {
        fprintf(stderr, "RegisterNatives failed for '%s'", className);
        return JNI_FALSE;
    }

    return JNI_TRUE;
}

/*
 * Register native methods for all classes we know about.
 */
static int registerNatives(JNIEnv* env)
{
  if (!registerNativeMethods(env, classPathName,
                 methods, sizeof(methods) / sizeof(methods[0]))) {
    return JNI_FALSE;
  }

  return JNI_TRUE;
}

/*
 * Set some test stuff up.
 *
 * Returns the JNI version on success, -1 on failure.
 */

typedef union {
    JNIEnv* env;
    void* venv;
} UnionJNIEnvToVoid;

jint JNI_OnLoad(JavaVM* vm, void* reserved)
{
    UnionJNIEnvToVoid uenv;
    uenv.venv = NULL;
    jint result = -1;
    JNIEnv* env = NULL;
    
    printf("JNI_OnLoad");

    if (vm->GetEnv(&uenv.venv, JNI_VERSION_1_4) != JNI_OK) {
        fprintf(stderr, "GetEnv failed");
        goto bail;
    }
    env = uenv.env;

    if (!registerNatives(env)) {
        fprintf(stderr, "registerNatives failed");
    }
    
    result = JNI_VERSION_1_4;
    
bail:
    return result;
}