package com.aruba.ndkapplication;
public class JniUtils {
static {
System.loadLibrary("native-lib");
}
public static native String stringFromJNI();
}
JNIEXPORT jstring JNICALL native_stringFromJNI(JNIEnv *env, jclass type) {
return env->NewStringUTF("C++");
}
static const JNINativeMethod gMethods[] = {
{
"stringFromJNI", "()Ljava/lang/String;", (void *) native_stringFromJNI
}
};
static int registerNatives(JNIEnv* env)
{
LOGI("registerNatives begin");
jclass clazz;
//找到java的类
clazz = env -> FindClass("com/aruba/ndkapplication/JniUtils");
if (clazz == NULL) {
LOGI("clazz is null");
return JNI_FALSE;
}
if (env->RegisterNatives(clazz, gMethods, NELEM(gMethods)) < 0) {
LOGI("RegisterNatives error");
return JNI_FALSE;
}
return JNI_TRUE;
}
JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved){
LOGI("jni_OnLoad begin");
JNIEnv* env = NULL;
if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {
LOGI("ERROR: GetEnv failed\n");
return -1;
}
assert(env != NULL);
registerNatives(env);
return JNI_VERSION_1_4;
}
#include <jni.h>
#include <string>
#include <android/log.h>
#include <assert.h>
#define TAG "C++"
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, TAG, __VA_ARGS__)
#define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0])))
extern "C"
JNIEXPORT jstring JNICALL native_stringFromJNI(JNIEnv *env, jclass type) {
return env->NewStringUTF("C++");
}
static const JNINativeMethod gMethods[] = {
{
"stringFromJNI", "()Ljava/lang/String;", (void *) native_stringFromJNI
}
};
static int registerNatives(JNIEnv* env)
{
LOGI("registerNatives begin");
jclass clazz;
//找到java的类
clazz = env -> FindClass("com/aruba/ndkapplication/JniUtils");
if (clazz == NULL) {
LOGI("clazz is null");
return JNI_FALSE;
}
if (env->RegisterNatives(clazz, gMethods, NELEM(gMethods)) < 0) {
LOGI("RegisterNatives error");
return JNI_FALSE;
}
return JNI_TRUE;
}
JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved){
LOGI("jni_OnLoad begin");
JNIEnv* env = NULL;
if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {
LOGI("ERROR: GetEnv failed\n");
return -1;
}
assert(env != NULL);
registerNatives(env);
return JNI_VERSION_1_4;
}
静态注册: 每个class都需要使用javah生成一个头文件,并且生成的名字很长书写不便;初次调用时需要依据名字搜索对应的JNI层函数来建立关联关系,会影响运行效率 用javah 生成头文件方便简单 动态注册: 使用一种数据结构JNINativeMethod来记录java native函数和JNI函数的对应关系 移植方便(一个java文件中有多个native方法,java文件的包名更换后)