JNI_onLoad 动态注册函数

#include
#include
#include
#include
#include
#include


#define JNIREG_CLASS "com/example/hellojni/HelloJni"
JNIEXPORT jstring JNICALL native_printf(JNIEnv *env, jclass clazz)
{
    __android_log_print(ANDROID_LOG_ERROR, "tag", "call in java");
    return (*env)->NewStringUTF(env,"this is a test for Jni_onload");
}


static JNINativeMethod gMethods[] = {
    {"native_printf", "()Ljava/lang/String;", (void*)native_printf},
};


static int registerNativeMethods(JNIEnv* env, const char* className,
                                 JNINativeMethod* gMethods, int numMethods)
{
    jclass clazz;
    clazz = (*env)->FindClass(env, className);
    if (clazz == NULL) {
        return JNI_FALSE;
    }
    if ((*env)->RegisterNatives(env, clazz, gMethods, numMethods) < 0) {
        return JNI_FALSE;
    }
    return JNI_TRUE;
}


static int registerNatives(JNIEnv* env)
{
    if (!registerNativeMethods(env, JNIREG_CLASS, gMethods,
        sizeof(gMethods) / sizeof(gMethods[0])))
        return JNI_FALSE;


    return JNI_TRUE;
}


JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved)
{
    JNIEnv* env = NULL;
    jint result = -1;


    if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
        __android_log_print(ANDROID_LOG_ERROR, "tag", "load library error 1");
        return JNI_ERR;
    }
    assert(env != NULL);


    if (!registerNatives(env)) {
        __android_log_print(ANDROID_LOG_ERROR, "tag", "load library error 2");
        return JNI_ERR;
    }
    result = JNI_VERSION_1_4;
    __android_log_print(ANDROID_LOG_ERROR, "tag", "load library success: %d", result);
    return result;
}


JNIEXPORT void JNICALL JNI_OnUnload(JavaVM* vm, void* reserved)
{
    __android_log_print(ANDROID_LOG_ERROR, "tag", "library was unload");
}