通过多个 jni 调用保持某种 c++ 对象处于活动状态 [英] keep some sort of c++ object alive over multiple jni calls

问题描述

我的 java 代码将调用现有的 c++ 代码来解析文件.它将生成一个保存许多数据的对象.我将调用jni的第二种方法来访问这些数据，当我调用第二种方法时，我必须再次解析文件.这显然是正确的行为.

My java code will call the exist c++ code to parse the file. it will generate an object which keep many data. I will call the jni's second method to access such data, When I call the second method, I have to parse the file again. it is obviously the right behavior.

有没有办法解决这个问题?顺便说一句:我是 C++ 新手.

Is there a way to handle this ? BTW: I am newly to c++.

推荐答案

我不确定我是否理解你的问题.但我猜你想要做的是让某种 c++ 对象在多个 jni 调用中保持活跃.

I am not sure if I understand your question correct. But I guess what you want to do is to keep some sort of c++ object alive over multiple jni calls.

你可以做很多事情.首先解析您的文件并将您的 c++ 对象存储在全局变量中.这是最简单的解决方案，但不是很好.

You can do multiple things. First parse your file and store your c++ object in a global variable. This is the simplest solution but not a nice one.

您还可以将 c++ 对象的生命周期移到 java 中.

You can also move the life cycle of your c++ object into java.

jlong java_some_class_jni_method(...)
{
    .... parse your text file ....
    MyParseclass* cls = new MyParseclass(...);
    ....
    return (jlong) cls;
}

但请记住，您需要再次删除这个原生 c++ 类.所以你需要一个 jni 方法，并且一定要调用它.

But keep in mind that you need to delete this native c++ class again. So you need a jni method to this and be sure to call it.

void java_some_calls_jni_method(..., jlong clsPtr)
{
    MyParseclass* cls = (MyParseclass*)clsPtr;
    ... do maybe do something with cls and access the data...
    delete cls; // do not use the jlong again in any call
}

顺便说一句:如果您发布一些代码会更有帮助.但我希望这里的伪代码能有所帮助.

BTW: It would be much more helpful if you would post some code. But I hope this pseudo code here helps a little.

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