Android studio 中JNI JAVA和C++互调

android 中java调用C++ 定义接口类

package test.simulateapp;/** * Created by zhu on 17-6-22. */public class JniInfence {    public static native void init(JNICallJava jniCallJava,String user,String passwd,String addr,int port);    public static native void sendSet(int index,String str,String s);    static {        System.loadLibrary("native-lib");    }}

通过javah编译生成对应C头文件，但这种方式由于函数名太长，一般修改还要编译我不是很喜欢，就不介绍了，这里介绍的是JVM的隐式注册，JNI_OnLoad和JNI_OnUnload。在android 启动时会调用JNI_OnLoad函数通过他注册上面接口类的两个函数入口，使用如下：

jint JNI_OnLoad(JavaVM *vm,void *reserved);void JNI_OnUnload(JavaVM *vm,void *reserved);void InitParameter(JavaVM *vm);void init(JNIEnv *env, jobject,jobject,jstring ip,jstring i,jstring p,jint);//void send_set(JNIEnv *env, jobject,jint,jstring str,jstring ip);#define FUNCTIONS (2)JNINativeMethod ParameterSetFunctions[FUNCTIONS] = {        { "init","(Ltest/simulateapp/JNICallJava;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;I)V",(void*) init },        { "sendSet","(ILjava/lang/String;Ljava/lang/String;)V",(void*) send_set },};jint JNI_OnLoad(JavaVM *vm,void *reserved){    __android_log_print(ANDROID_LOG_ERROR,"JNI_OnLoad","JNI_OnLoad初始化[%d].", __LINE__);    __g_jvm = vm;    InitParameter(__g_jvm);    return JNI_VERSION_1_4;}void JNI_OnUnload(JavaVM *vm,void *reserved){    __android_log_print(ANDROID_LOG_ERROR,"JNI_OnUnload","JNI 结束 [%d].", __LINE__);}void InitParameter(JavaVM *vm){    JNIEnv* env = 0; //注册时在JNIEnv中实现的，所以必须首先获取它    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 ;    jclass clazz = env->FindClass( "test/simulateapp/JniInfence"); //这里可以找到要注册的类，前提是这个类已经加载到java虚拟机中。 这里说明，动态库和有native方法的类之间，没有任何对应关系。    if(clazz == 0)    {        return ;    }    g_parameter_class = (jclass)env->NewGlobalRef(clazz);    if(env->RegisterNatives( g_parameter_class,ParameterSetFunctions, FUNCTIONS)!= JNI_OK) //这里就是关键了，把本地函数和一个java类方法关联起来。不管之前是否关联过，一律把之前的替换掉！    {        return ;    }    g_server_class = env->FindClass( "test/simulateapp/JNICallJava");    if(g_server_class == 0)    {        return ;    }    g_severeCid = env->GetMethodID(g_server_class, "update_data", "(IILjava/lang/String;I)V");//C调JAVA注册    if (g_severeCid == 0) {        __android_log_print(ANDROID_LOG_ERROR,"Android_Play",                            "%s: could not get g_severeCid ID", __FUNCTION__);    }    return;}/* C++调JAVA */void update_data(int index,int cmd,string ss,int strategy_id){    if (__g_jvm)    {        bool isAttached = false;        JNIEnv* env = NULL;        if (__g_jvm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {            // try to attach the thread and get the env            // Attach this thread to JVM            jint res = __g_jvm->AttachCurrentThread(&env, NULL);            // Get the JNI env for this thread            if ((res < 0) || !env) {                __android_log_print(ANDROID_LOG_DEBUG,"Android_Play",                                    "%s: Could not attach thread to JVM (%d, %p)",                                    __FUNCTION__, res, env);                env = NULL;            } else {                isAttached = true;            }        }        if(env)        {            if (g_severeCid)            {                env->CallVoidMethod((jobject)g_call_java_handler, g_severeCid,index,cmd,env->NewStringUTF(ss.c_str()),strategy_id);            }        }        if (isAttached) {            if (__g_jvm->DetachCurrentThread() < 0) {            }        }    }    return;}

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