andorid ndk 各种坑啊 记录下

android jni代码回调java的问题
由于多线程原因会导致找不到java类，无法call函数的问题
问题1找不到java类
在JNI_OnLoad的时候 保存下来

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved){    g_vm = vm;    JNIEnv* env = NULL;    jint result = -1;    if (vm->GetEnv((void**) &env, JNI_VERSION_1_4) != JNI_OK) {        return -1;    }    assert(env != NULL);    register_location_methods(env);    result = JNI_VERSION_1_4;    return result;}int register_location_methods(JNIEnv *env){    jniEnv = env;    jclass clazz;    clazz = env->FindClass("com/TongBan/Chat/NetBilling");    if (clazz == NULL) {        return -1;    }    JNetBilling = clazz;    onReceivedMsgType = env->GetStaticMethodID(clazz,                    "OnReceivedMsgType", "(I)V");//    env->CallStaticVoidMethod(JNetBilling, onReceivedMsgType, 1);    return 0;}

问题2多线程回调call函数
此处生成的JNIEnv无法获取到class 函数 等 需要之前保存好的全局变量

bool isAttacked = false;    JNIEnv* env;    int status = g_vm->GetEnv((void **) &env, JNI_VERSION_1_4);    if (status < 0) {        status = g_vm->AttachCurrentThread(&env, NULL);        if (status < 0) {            return len;        }        isAttacked = true;    }    env->CallStaticVoidMethod(JNetBilling,onReceivedMsgType,iMsgType);    if (isAttacked) {        g_vm->DetachCurrentThread();    }

输出问题由于还是比较喜欢cout就百度了个cout输出到logCat日志的

int iMsgType = MSG_PACKET::GetMsgType(kBuffer);    StreamBuf g_StreamBuf;    std::cout.rdbuf(&g_StreamBuf);    std::cout << iMsgType;//即可显示到logCat

#include <iostream>#include <streambuf>class StreamBuf : public std::streambuf{    enum    {        BUFFER_SIZE = 255,    };public:    StreamBuf()    {        buffer_[BUFFER_SIZE] = '\0';        setp(buffer_, buffer_ + BUFFER_SIZE - 1);    }    ~StreamBuf()    {        sync();    }protected:    virtual int_type overflow(int_type c)    {        if (c != EOF)        {            *pptr() = c;            pbump(1);        }        flush_buffer();        return c;    }    virtual int sync()    {        flush_buffer();        return 0;    }private:    int flush_buffer()    {        int len = int(pptr() - pbase());        if (len <= 0)            return 0;        if (len <= BUFFER_SIZE)            buffer_[len] = '\0';#ifdef ANDROID        android_LogPriority t = ANDROID_LOG_INFO;        __android_log_write(t, "JNI_DEBUG", buffer_);#else        printf("%s", buffer_);#endif        pbump(-len);        return len;    }private:    char buffer_[BUFFER_SIZE + 1];};

到这里 终于可以 互动了 android->服务器->android