JNI FindClass没找到课程？

Question

将此dll注入java程序时，程序立即停止响应。当我打开调试器时，它说我试图用env-> FindClass找到的类等于0x000000000000（NULL）。无法弄清楚为什么我确定给出的路径是正确的......

以下是我的测试项目的MainThread代码：

#include <Windows.h>
#include <jni.h>

DWORD WINAPI Main_Thread(LPVOID lpParam)
{
HMODULE m_hDllInstance = LoadLibraryA("jvm.dll");
JavaVM *jvm;
JNIEnv *env;

typedef jint(JNICALL * GetCreatedJavaVMs)(JavaVM**, jsize, jsize*);

GetCreatedJavaVMs jni_GetCreatedJavaVMs = (GetCreatedJavaVMs)GetProcAddress(m_hDllInstance, "JNI_GetCreatedJavaVMs");

jint size = 1;
jint vmCount;

jint ret = jni_GetCreatedJavaVMs(&jvm, size, &vmCount);
jint rc = jvm->AttachCurrentThread((void **)& env, NULL);

//NULL?
jclass PlayerControllerMP = env->FindClass("net/minecraft/client/multiplayer/PlayerControllerMP"); //NULL?

jmethodID constructor = env->GetStaticMethodID(PlayerControllerMP, "<init>", "(Minecraft, NetHandlerPlayClient)PlayerControllerMP");

jobject pcmpObj = env->NewObject(PlayerControllerMP, constructor);
jmethodID getReach = env->GetMethodID(PlayerControllerMP, "getBlockReachDistance", "()F");

while (!GetAsyncKeyState(VK_END))
{
    env->CallFloatMethod(pcmpObj, getReach);
}

jvm->DetachCurrentThread();
return S_OK;
}

感谢您的帮助，抱歉，如果代码看起来有点搞笑，则无法粘贴它。