JNI调用java自定义类

一，注册java方法和jni方法相对应

 static const JNINativeMethod gMethods[] = {
        //name   //signature   //funcPtr
        {"testObjectJNI","(Lcom/zero/sdk/jnitest/TestMsg;)I",(void *)jni_test},
};


JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved){
    JNIEnv* env = NULL;
    if(vm->GetEnv((void**)&env, JNI_VERSION_1_4) != JNI_OK) //从JavaVM获取JNIEnv，一般使用1.4的版本
        return -1;
    jclass clazz = env->FindClass(JAVA_CLASS_PATH);
    if (!clazz){
        LOGW("cannot get class");
        return -1;
    }
    if(env->RegisterNatives(clazz, gMethods, sizeof(gMethods)/sizeof(gMethods[0])))
    {
        LOGW("register native method failed!");
        return -1;
    }
    return JNI_VERSION_1_4;
}

二，通过接口传递java类
java定义接口

 private native int testObjectJNI(TestMsg responseMsg)

c++定义接口

static jint jni_test(JNIEnv* pEnv, jobject , jobject arg)
{}

三，java层创建对象传递并通过native接口传递到c++层

TestMsg testMsg = new TestMsg();
testMsg.msg = "server is hungry!";
testMsg.subTestMsg = new TestMsg.SubTestMsg();
testObjectJNI(testMsg); //调用native通信接口
System.out.println("=================code:"+testMsg.code+";msg:"+ testMsg.msg+";subMsg:"+testMsg.subTestMsg.subMsg);

四，c++层获取java类以及其成员数据并修改设置

const char* buf  = "code is success";
const char* subBuf  = "sub code is success";

static jint jni_test(JNIEnv* pEnv, jobject , jobject arg)
{
    jclass jcarg =GetClassOrDie(pEnv,arg);
    jfieldID iid = GetFieldIDOrDie(pEnv,jcarg, "code", "I");
    pEnv->SetIntField(arg,iid,200);
    jfieldID strid = GetFieldIDOrDie(pEnv,jcarg, "msg", "Ljava/lang/String;");

    SetChar2JString(pEnv,arg,strid,buf);

    jfieldID subMsgId = GetFieldIDOrDie(pEnv,jcarg,"subTestMsg","Lcom/zero/sdk/jnitest/TestMsg$SubTestMsg;");
    if (!subMsgId){
        LOGW("===========================subMsgId is null");
    }
    jobject subObj = pEnv->GetObjectField(arg, subMsgId);

    if (!subObj){
        LOGW("===========================subObj is null");
    }

    jclass subClass = FindClassOrDie(pEnv,"com/zero/sdk/jnitest/TestMsg$SubTestMsg");
    if (!subClass) {
        LOGW("===========================findClass is null");
    }
    jfieldID subStrid = GetFieldIDOrDie(pEnv,subClass,"subMsg", "Ljava/lang/String;");
    if (!subStrid){
        LOGW("===========================subStrid is null");
    }

    SetChar2JString(pEnv,subObj,subStrid,subBuf);

    return 0;
}

附完整实现code:
c++实现接口

#include <jni.h>
#include <string>
#include <android/log.h>
#include "core_jni_helpers.h"


#define TAG "SceneManager" // 这个是自定义的LOG的标识
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,TAG ,__VA_ARGS__) // 定义LOGD类型
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,TAG ,__VA_ARGS__) // 定义LOGI类型
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN,TAG ,__VA_ARGS__) // 定义LOGW类型
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG ,__VA_ARGS__) // 定义LOGE类型
#define LOGF(...) __android_log_print(ANDROID_LOG_FATAL,TAG ,__VA_ARGS__) // 定义LOGF类型



extern "C" JNIEXPORT jstring JNICALL
Java_com_zero_sdk_jnitest_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject obj) {
    std::string hello = "Hello from C++";
    jstring jstr = env->NewStringUTF(hello.c_str());
    return jstr;
}

const char* SCENE_REMOTE_PROXY_PATH = "com/zero/sdk/jnitest/MainActivity";
const char* buf  = "code is success";
const char* subBuf  = "sub code is success";

static jint jni_test(JNIEnv* pEnv, jobject , jobject arg)
{
    jclass jcarg =GetClassOrDie(pEnv,arg);
    jfieldID iid = GetFieldIDOrDie(pEnv,jcarg, "code", "I");
    pEnv->SetIntField(arg,iid,200);
    jfieldID strid = GetFieldIDOrDie(pEnv,jcarg, "msg", "Ljava/lang/String;");

    SetChar2JString(pEnv,arg,strid,buf);

    jfieldID subMsgId = GetFieldIDOrDie(pEnv,jcarg,"subTestMsg","Lcom/zero/sdk/jnitest/TestMsg$SubTestMsg;");
    if (!subMsgId){
        LOGW("===========================subMsgId is null");
    }
    jobject subObj = pEnv->GetObjectField(arg, subMsgId);

    if (!subObj){
        LOGW("===========================subObj is null");
    }

    jclass subClass = FindClassOrDie(pEnv,"com/zero/sdk/jnitest/TestMsg$SubTestMsg");
    if (!subClass) {
        LOGW("===========================findClass is null");
    }
    jfieldID subStrid = GetFieldIDOrDie(pEnv,subClass,"subMsg", "Ljava/lang/String;");
    if (!subStrid){
        LOGW("===========================subStrid is null");
    }

    SetChar2JString(pEnv,subObj,subStrid,subBuf);

    return 0;
}


static const JNINativeMethod gMethods[] = {
        //name   //signature   //funcPtr
        {"testObjectJNI","(Lcom/zero/sdk/jnitest/TestMsg;)I",(void *)jni_test},
};


JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved){
    JNIEnv* env = NULL;
    if(vm->GetEnv((void**)&env, JNI_VERSION_1_4) != JNI_OK) //从JavaVM获取JNIEnv，一般使用1.4的版本
        return -1;
    jclass clazz = env->FindClass(SCENE_REMOTE_PROXY_PATH);
    if (!clazz){
        LOGW("cannot get class SceneRemoteProxy");
        return -1;
    }
    if(env->RegisterNatives(clazz, gMethods, sizeof(gMethods)/sizeof(gMethods[0])))
    {
        LOGW("register native method failed!");
        return -1;
    }
    return JNI_VERSION_1_4;
}

java调用

    // Used to load the 'native-lib' library on application startup.
    static {
        System.loadLibrary("native-lib");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Example of a call to a native method
        TextView tv = findViewById(R.id.sample_text);
        TestMsg testMsg = new TestMsg();
        testMsg.msg = "server is hungry!";
        testMsg.subTestMsg = new TestMsg.SubTestMsg();
        // ResponseMsg resMsg = returnRespose();
        testObjectJNI(testMsg);
        System.out.println("=================code:"+testMsg.code+";msg:"+ testMsg.msg+";subMsg:"+testMsg.subTestMsg.subMsg);
    }

    /**
     * A native method that is implemented by the 'native-lib' native library,
     * which is packaged with this application.
     */
    public native String stringFromJNI();

    private native int testObjectJNI(TestMsg responseMsg);

java数据结构

package com.zero.sdk.jnitest;

public class TestMsg {
    public String msg;
    public int code;
    public SubTestMsg subTestMsg;
    public static class SubTestMsg{
        public String subMsg;
    }
}

jni 方法封装类

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef CORE_JNI_HELPERS
#define CORE_JNI_HELPERS

// Defines some helpful functions.

#ifdef NDEBUG
#define REG_JNI(name)      { name }
    struct RegJNIRec {
        int (*mProc)(JNIEnv*);
    };
#else
#define REG_JNI(name)      { name, #name }
struct RegJNIRec {
    int (*mProc)(JNIEnv*);
    const char* mName;
};
#endif

static inline jclass FindClassOrDie(JNIEnv* env, const char* class_name) {
    jclass clazz = env->FindClass(class_name);
    return clazz;
}

static inline jclass GetClassOrDie(JNIEnv* env, jobject arg) {
    jclass jcarg = env->GetObjectClass(arg);
    return jcarg;
}

static inline jfieldID GetFieldIDOrDie(JNIEnv* env, jclass clazz, const char* field_name,
                                       const char* field_signature) {
    jfieldID res = env->GetFieldID(clazz, field_name, field_signature);
    return res;
}

static inline jmethodID GetMethodIDOrDie(JNIEnv* env, jclass clazz, const char* method_name,
                                         const char* method_signature) {
    jmethodID res = env->GetMethodID(clazz, method_name, method_signature);
    return res;
}

static inline jfieldID GetStaticFieldIDOrDie(JNIEnv* env, jclass clazz, const char* field_name,
                                             const char* field_signature) {
    jfieldID res = env->GetStaticFieldID(clazz, field_name, field_signature);
    return res;
}

static inline jmethodID GetStaticMethodIDOrDie(JNIEnv* env, jclass clazz, const char* method_name,
                                               const char* method_signature) {
    jmethodID res = env->GetStaticMethodID(clazz, method_name, method_signature);
    return res;
}

static inline void SetChar2JString(JNIEnv* env,jobject obj,jfieldID id, const char* value) {
    jstring strBuf = env->NewStringUTF(value);
    env->SetObjectField(obj, id, strBuf);
}

template <typename T>
static inline T MakeGlobalRefOrDie(JNIEnv* env, T in) {
    jobject res = env->NewGlobalRef(in);
    return static_cast<T>(res);
}




#endif  // CORE_JNI_HELPERS