Question

我有一个处理位图并返回String的Java方法。当我从JNI（VS 2010）调用此方法时，它可以工作，但如果我多次调用此方法，这个过程的记忆长大直到崩溃。使用大量内存的指令是：

jbyteArray jBuff = _env->NewByteArray(b->Length);

我的代码：

static jobject staticArray=0;

System::String^ MyClass::ExecuteJavaMethod(System::Drawing::Bitmap^ bmp)
{
    JNIEnv *_env;
    System::String^ out;
    unsigned const char * buff;

    int res = jvm->AttachCurrentThread((void **)&_env, NULL);

    if (jvm->GetEnv((void**) &_env, JNI_VERSION_1_6) != JNI_OK)
    {
        return "GetEnv ERROR";
    }

    //save the bitmap in the stream
    MemoryStream^ ms = gcnew MemoryStream();
    bmp->Save(ms, ImageFormat::Bmp);

    //get the bitmap buffer
    array<unsigned char>^b = ms->GetBuffer() ;

    //unmanaged conversion
    buff = GetUnmanaged(b,b->Length);


    //fill the buffer
    jbyteArray jBuff = _env->NewByteArray(b->Length);       
    _env->SetByteArrayRegion(jBuff, 0, b->Length, (jbyte*) buff);

    //call the java method
    jstring str = (jstring) _env->CallStaticObjectMethod (  Main,
                                javaMethod,
                                jBuff);



    // _env->ReleaseByteArrayElements(jBuff,(jbyte*)buff), 0); //NOT WORKING

    //staticArray= _env->NewGlobalRef(jBuff);  NOT
    //_env->DeleteLocalRef(jBuff);             WORKING  


    //return the string result of the java method
    return gcnew String(env->GetStringUTFChars(str, 0));

}

Answer 1

答案是：_env->DeleteLocalRef(jBuff);

Answer 2

您没有为Java Native Interface Specification中请求的每个DetachCurrentThread()致电AttachCurrentThread()。这使得本地引用（jBuff和str）无法自动释放。此外，需要释放通过const char*获取的GetStringUTFChars()。

正确的方法是改变

return gcnew String(env->GetStringUTFChars(str, 0));

到

const char* cstr = env->GetStringUTFChars(str, 0);
System::String^ retstr = gcnew String(cstr);
env->ReleaseStringUTFChars(str, cstr);
jvm->DetachCurrentThread();
return retstr;

JNI NewByteArray内存泄漏

2 个答案: