从调用C ++方法Java函数 [英] Call Java function from C++ method

问题描述

我现在面临的麻烦调用从C ++方法的Java函数。下面是我在做什么。

I am facing trouble calling a Java function from C++ method. The following is what I am doing

我的Java类

package com.q.IT;

public class Carv {

public boolean isValidRatio(float a, float b)
{

       //do something
       return True;
    }
}

我的C ++方法

My C++ method

void printAndValidateResults() {

    JNIEnv *env;
jclass ItClass =env->FindClass("com/q/IT/Carv");
jobject object = env->AllocObject(ItClass);
jmethodID isValidRatioID = env->GetMethodID(ItClass,"isValidRatio", "(FF)Z");
    bool retVal = env->CallBooleanMethod(object, isValidRatioID, 1.0f,2.0f);
}

我收到以下错误

06-23 23:35:03.459: A/libc(15758): Fatal signal 11 (SIGSEGV) at 0xe92d43a4 (code=1), thread 16113 (AsyncTask #2)

正如你所看到的，C ++的方法是一个普通的C ++方法，而不是像

As you can see, the C++ method is a normal C++ method and not something like

JNIEXPORT无效JNICALL
Java_com_q_IT_blahblah（JNIEnv的*，jobject）
{

，我想保持这种方式。这次事故发生在这里。

, I'd like to keep it that way. The crash happens here

jclass ItClass =env->FindClass("com/q/IT/Carv");

我不太知道该怎么初始化* ENV来。

I am not quite sure what to initialize *env to.

推荐答案

作为一个例子，检查的创建从C​​ 一个JVM。它显示了一个示例程序创建一个JVM，并调用一个方法。如果JVM已经存在;例如C程序是由Java程序（回调的情况），您可以缓存的JNIEnv *指针调用。

As an example, check Creating a JVM from C. It shows a sample procedure to create a JVM and invoke a method. If the JVM already exists; e.g. your C program is invoked by the Java program (callback situation), you can cache the JNIEnv* pointer.

作为一个建议，要小心缓存指针JVM对C / C ++，有参与，以什么可以缓存，它可在以后调用一些语义。

As an advice, be careful caching pointers to the JVM from C/C++, there are some semantics involved as to what you can cache and it could be invoked later on.

来源：如何从C调用Java函数++

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