JNI动态注册封装C++版

JNIEXPORT jstring JNICALL Java_com_biumall_jni_one_Hello_hello
  (JNIEnv * env , jclass jclazz){
    return (*env)->NewStringUTF(env, "Hello World !---from JNI");
};

JNIEXPORT jstring JNICALL Java_com_biumall_jni_one_Hello_hello
  (JNIEnv * env , jclass jclazz){
    return env->NewStringUTF("Hello World !---from JNI");
};

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_LDLIBS := -llog
LOCAL_MODULE    := Hello
​
# C语言
LOCAL_SRC_FILES := Hello.c
# C++ 
LOCAL_SRC_FILES := Hello.cpp
​
include $(BUILD_SHARED_LIBRARY)

public class Hello {
    private final String TAG = "from_dynamic_java_";
    //1. load Hello.so
    static {
        System.loadLibrary("Hello");
    }
    // 2. define native computer()
    public static native int computer(String type, int a, int b);
    
    public int add(int x, int y) {
        return x + y;
    }
    public int sub(int x, int y) {
        return x - y;
    }
}

#include <android/log.h>
​
//定义TAG日志打印
#define LOG_TAG "from_dynamic_jni_"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)

#include <jni.h>
​
//获取数组大小
#define ARRAY_LENGTH(x) ((int)(sizeof(x) / sizeof((x)[0])))
​
//注册本地方法
int registerNativeMethods(JNIEnv *env, const char *className, JNINativeMethod *methods,
                          int methods_size) {
    jclass clazz = env->FindClass(className);
    if (!clazz) {
        return JNI_ERR;
    }
    int result = env->RegisterNatives(clazz, methods, methods_size);
    if (result < 0) {
        return JNI_ERR;
    }
    return JNI_OK;
}

#include "JNICommon.h"
#include "Log.h"
#include<string.h>
​
/**
 * ---------------------------第一步 start ---------------------------
 * 定义Hello.java类路径[包名+类名，只不过.换成了/]
 * 包名+类名：com.biumall.dynamic.one.Hello
 */
#define DYNAMIC_CLASS "com/biumall/dynamic/one/Hello"
/**
 * ---------------------------第一步  end  ---------------------------
 */
​
/**
 * ---------------------------第二步 start ---------------------------
 * c_add()用于调用Java方法
 * @param env env
 * @param jclazz jclazz
 * @param x x
 * @param y y
 * @return
 */
int c_add(JNIEnv *env, jclass jclazz, int x, int y) {
    jmethodID methodID = env->GetMethodID(jclazz, "add", "(II)I");
    jobject object = env->AllocObject(jclazz);
    return env->CallIntMethod(object, methodID, x, y);
}
​
/**
 * c_sub()用于调用Java方法
 * @param env env
 * @param jclazz jclazz
 * @param x x
 * @param y y
 * @return
 */
int c_sub(JNIEnv *env, jclass jclazz, int x, int y) {
    jmethodID methodID = env->GetMethodID(jclazz, "sub", "(II)I");
    jobject object = env->AllocObject(jclazz);
    return env->CallIntMethod(object, methodID, x, y);
}
​
/**
 * 本地方法computer实现
 */
JNIEXPORT jint JNICALL native_computer(JNIEnv *env, jclass jclazz, jstring type, jint a, jint b) {
    const char *charType = env->GetStringUTFChars(type, 0);
    LOGD("native_computer : %s ", charType);
    int count;
    if (!strcmp(charType, "-")) {
        count = c_sub(env, jclazz, a, b);
    } else if (!strcmp(charType, "+")) {
        count = c_add(env, jclazz, a, b);
    }
    env->ReleaseStringUTFChars(type, charType);
    return count;
}
/**
 * ---------------------------第二步  end  ---------------------------
 */
​
/**
 * ---------------------------第三步 start ---------------------------
 * 定义Java和JNI函数的绑定表
 * 方法数组，分别为：(native方法 ， 方法签名 ， 函数指针[JNI中需要实现的方法名])
 * 通过javac和javap 获取 方法签名
 */
JNINativeMethod method_table[] = {
        {"computer", "(Ljava/lang/String;II)I", (void *) native_computer},
};
/**
 * ---------------------------第三步  end  ---------------------------
 */
​
/**
 * ---------------------------第四步 start ---------------------------
 * 注册本地方法
 */
JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved ){
    JNIEnv *env = NULL;
    int result = vm->GetEnv((void **) &env, JNI_VERSION_1_6);
    LOGD("JNI_OnLoad 1 result : %d", result);
    if(result != JNI_OK){
        return JNI_ERR;
    }
    result = registerNativeMethods(env, DYNAMIC_CLASS, method_table, ARRAY_LENGTH(method_table));
    LOGD("JNI_OnLoad 2 result : %d", result);
    if(result != JNI_OK){
        return JNI_ERR;
    }
    return JNI_VERSION_1_6;
}
/**
 * ---------------------------第四步  end  ---------------------------
 */

APP_ABI := arm64-v8a

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_LDLIBS := -llog
LOCAL_MODULE    := Hello
LOCAL_SRC_FILES := Hello.cpp
include $(BUILD_SHARED_LIBRARY)