android JNI 多线程 C函数回调

JNIEnv *env指针不可为多个线程共用,但是java虚拟机的JavaVM指针是整个jvm公用的，我们可以通过JavaVM来得到当前线程的JNIEnv指针.

示例代码：

#include

static JavaVM* g_vm = NULL;
static jclass g_mainActivityClass = NULL;
static jmethodID g_ID = NULL;

jint JNI_OnLoad(JavaVM* vm, void* reserved)
{
   JNIEnv * env = NULL;
   if(g_vm == NULL){
      g_vm = vm;
   }
    if ( (*g_vm)->GetEnv(vm,(void**)&env, JNI_VERSION_1_2) != JNI_OK) {
        LOGD("ERROR: GetEnv failed");
        return -1;
    };
   jclass mainActivityClass = (*env)->FindClass(env,"com/ht/htvideodemo/activity/MainActivity");
   if( mainActivityClass == NULL){
      return -2;
   }
   g_mainActivityClass = (*env)->NewGlobalRef(env,mainActivityClass);
    return JNI_VERSION_1_2;
}

//C函数的回调

static void CallBack(HANDLE hHandle, DATA *pData, void *pUser) {
   jint result;
   JNIEnv * env = NULL;
   if(g_vm == NULL){return;}
   result = (*g_vm)->AttachCurrentThread(g_vm,&env, NULL);
   if(result == JNI_OK) {
       if (g_mainActivityClass != NULL){
          jclass clazz = (*env)->GetObjectClass(env,g_mainActivityClass);
          if(mpkt->nMediaType == HTC_MEDIA_VIDEO){
           int size = mpkt->nSize;
           jbyteArray bytearray;
           bytearray = (*env)->NewByteArray(env,size);
           (*env)->SetByteArrayRegion(env,bytearray,0,size,mpkt->pBuffer);
           g_ID = (*env)->GetStaticMethodID(env,g_mainActivityClass,"test","([B)V");
           (*env)->CallStaticVoidMethod(env,g_mainActivityClass,g_ID,bytearray);
          }
       }

}

(*g_vm)->DetachCurrentThread(g_vm); //释放线程，否则会导致内存泄漏

}

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