I am writing some code to get a spawned thread to call a Java static method from C ++.
The bits that call the method work fine if placed in a native call from Java, but not from a thread with JNIEnv attached.
I installed JavaVM * as follows:
jint JNI_OnLoad(JavaVM* jvm, void* reserved) { LOGI("Setting Java Virtual Machine"); ThreadJNIEnvironment::javaVM = jvm; return JNI_VERSION_1_6; }
It is caused.
Then I create another thread and from this thread I do the following:
JNIEnv* env; jint ret = ThreadJNIEnvironment::javaVM->AttachCurrentThread(&env, NULL); LOGI("AttachCurrentThread returned %d", ret); jclass interfaceClass = env->FindClass("com/ecmsys/mcb/model/McbInterface"); jmethodID testMethod = env->GetStaticMethodID(interfaceClass, "Test", "()V"); env->CallStaticVoidMethod(interfaceClass, testMethod);
AttachCurrentThread returns 0.
GetStaticMethod explodes, although with the following error:
Fatal signal 11 (SIGSEGV) at 0x0000002c (code=1).....
I just don’t see what I did to upset him ... oh wait ... you cannot access Java application classes from the spawned thread without doing some settings ...
jint JNI_OnLoad(JavaVM* jvm, void* reserved) { LOGI("Setting Java Virtual Machine"); ThreadJNIEnvironment::javaVM = jvm; JNIEnv* env; jvm->AttachCurrentThread(&env, NULL); jclass mcbInterface = env->FindClass("com/ecmsys/mcb/model/McbInterface"); ThreadJNIEnvironment::interfaceClass = env->NewGlobalRef(mcbInterface); return JNI_VERSION_1_6; }
Then do the following:
JNIEnv* env; jint ret = ThreadJNIEnvironment::javaVM->AttachCurrentThread(&env, NULL); LOGI("AttachCurrentThread retured %d", ret); if(ThreadJNIEnvironment::interfaceClass) { jmethodID testMethod = env-->GetStaticMethodID(static_cast<jclass>ThreadJNIEnvironment::interfaceClass), "Test", "()V"); env->CallStaticVoidMethod(static_cast<jclass>(ThreadJNIEnvironment::interfaceClass), testMethod); } ThreadJNIEnvironment::javaVM->DetachCurrentThread();
You live and study!