Comment appeler l'API Java à partir du thread NDK C ++?

Je tiens à appeler l'API Java de NDK C++ thread, mais env->FindClass() retourne 0. Mais quand je l'appelle API Java dans le thread principal, il fonctionne bien. J'ai déjà appeler AttachCurrentThread() dans le fil, quelqu'un peut-il m'aider?

Voici le code source:

DE CODE JAVA:

public class simple_test extends Activity {
    ...
    //This functin will be called in C++
    public void PrintNdkLog(String slog) {
        Log.e(logTagNDK, slog);
        return;
    }
}

CODE C++:

static JavaVM* g_JavaVM = NULL;
jobject getInstance(JNIEnv *env, jclass obj_class)
{
jmethodID  c_id = env->GetMethodID(obj_class, "<init>", "()V");
jobject obj = env->NewObject(obj_class, c_id);
return obj;
}
//JNI OnLoad
JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved)
{
g_JavaVM = jvm;
return JNI_VERSION_1_6;
}
//Call JAVA API "PrintNdkLog" in this function
void PrintNdkLog(char *lpLog)
{
if (g_JavaVM == NULL)
return;
JNIEnv *env = NULL;
g_JavaVM->GetEnv((void**)&env, JNI_VERSION_1_6);
if (env == NULL)
return;
jclass cls = env->FindClass("com/myndk/simple_test");
if (cls != 0) //**cls will be 0 when PrintNdkLog() is called in thread**
{
LOGE("FindClass error %p", cls);
}
else
{
jmethodID mid;
jobject obj;
obj = getInstance(env, cls);
mid = env->GetMethodID(cls, "PrintNdkLog", "(Ljava/lang/String;)V");
if (mid != 0)
{
jstring jstrMSG = env->NewStringUTF(lpLog);
env->CallVoidMethod(obj, mid, jstrMSG);
}
}
}
//Call JAVA API in thread
static void* thread_test(void* ptr)
{
JNIEnv *envLocal;
int status = g_JavaVM->GetEnv((void **) &envLocal, JNI_VERSION_1_6);
if (status == JNI_EDETACHED)
{
status = g_JavaVM->AttachCurrentThread(&envLocal, NULL);
if (status != JNI_OK)
LOGE("AttachCurrentThread failed %d",status);
}
PrintNdkLog("bbb"); //This JAVA callback failed, and printed "FindClass error"
}
//Create thread
int NdkThread(AFX_THREADPROC pfnThreadProc, LPVOID pParam, int nPriority)
{
PrintNdkLog("aaa"); //This JAVA callback runs well
pthread_t pid;
pthread_create(&pid, NULL, thread_test, pParam);
}

source d'informationauteur airun

  1. 5

    J'ai résolu maintenant.
    Dans NDK natif des threads, uniquement peut appeler statique de l'API Java. Si vous appelez env->FindClass(), il déclenche une exception.
    http://android.wooyd.org/JNIExample a donné l'info en détail.

  2. 0

    Suggère de prendre un coup d'oeil sur AttachCurrentThread.

    Voici un exemple de code pour faire ça:

    //Global variable
JavaVM *g_jvm = NULL;  //Get g_jvm from jni main thread use env->GetJavaVM(&g_jvm);
jobject g_obj = NULL;  //Where the java function exist. (some activity)
//Get env in thread function and attach the env
JNIEnv *env;
if(g_jvm->AttachCurrentThread(&env, NULL) != JNI_OK)
{
LOGD("%s: AttachCurrentThread() failed", __FUNCTION__);
}
const char * fnName ="somFunctionInYourJava"; //which should be "pulic void somFunctionInYourJava(String input);"
jstring retStr = env->NewStringUTF(str);
jclass cls = env->GetObjectClass(thiz);
jmethodID messageMe = env->GetMethodID(cls, fnName, "(Ljava/lang/String;)V");
env->CallVoidMethod(thiz, messageMe, retStr);
//Detach thread and release related resource    
if(g_jvm->DetachCurrentThread() != JNI_OK)
{
LOGD("%s: DetachCurrentThread() failed", __FUNCTION__);
}