C ++ std :: string到jstring，长度固定 [英] C++ std::string to jstring with a fixed length

问题描述

我正在尝试将C ++ std :: string转换为jstring并返回它。这很容易

I'm trying to turn a C++ std::string into a jstring and return it. This would be easy enough with

JNIEnv*->NewStringUTF(stdString.c_str())

但问题是我正在转换的字符串几乎随机散布了空字符。这是 c_str（）的问题，但不是 std :: string 。 NewStringUTF 只会捕获完整 std :: string 的一部分。有一些希望， std :: string 有一个 length（）函数，它获取全长，忽略有问题的char * \0 字符。

but the problem is that the string I'm converting has almost randomly interspersed null characters in it. This is a problem for the c_str(), but not the std::string. NewStringUTF will only catch a portion of the full std::string. There is some hope in that the std::string has a length() function, which gets the full length, ignoring the problematic char* \0 characters.

有一个单独的函数NewString ，它接受一个jchar *和一个jsize *，所以看起来很有希望，但是我无法将std :: string正确转换为jchar *。我试过把它变成一个字节数组，但我可能做得不对。我有进一步的问题，将 length（）给出的int转换为jsize，这是NewString调用所需要的。

There's a separate function NewString that takes in a jchar* and a jsize*, so that looks promising, but I can't get the std::string converted properly to the jchar*. I tried making it a byte array, but I probably wasn't doing it right. I had further problems converting the int given by the length() into a jsize, which was required by the NewString call.

我已经用 vector< char>做了一些工作。 byteArray（stdString.begin（），stdString.end（）），但这并没有让我走得太远，可能是因为这弄乱了原始字符串是什么。

I have done a bit of work with vector<char> byteArray(stdString.begin(), stdString.end()), but that didn't get me very far, probably because that is messing up what the original string is.

这是我的基本启动函数，它使用没有空字符的字符串：

Here is the basic starter function I have, which worked with strings without null chars:

jstring StringToJString(JNIEnv * env, const std::string & nativeString) {
    return env->NewStringUTF(nativeString.c_str());
}

作为旁注，此函数正在JNI包装器文件中使用返回一个对象的 std :: string 。

As a side note, this function is being used inside a JNI wrapper file for returning an object's std::string.

感谢您提供任何帮助或信息来源！

Thanks for any help or information sources!

推荐答案

我根据RedAlert的建议制定了自己的解决方法。

I made my own workaround solution taking RedAlert's advice.

Java现在需要一个字节[来自本机电话：

Java now expects a byte[] from the native call:

private native byte[] toString(long thiz);

toString方法现在在 std :: string中调用此方法：

The toString method now calls this method inside it on a std::string:

jbyteArray StringToJByteArray(JNIEnv * env, const std::string &nativeString) {
    jbyteArray arr = env->NewByteArray(nativeString.length());
    env->SetByteArrayRegion(arr,0,nativeString.length(),(jbyte*)nativeString.c_str());
    return arr;
}

并且java级别接收如下数据：

And the java level receives the data like this:

byte[] byteArray = toString(mNativeInstance);
String nativeString = "";
try {
    nativeString = new String(byteArray, "UTF-8");
} catch (UnsupportedEncodingException e) {
    Log.e(TAG, "Couldn't convert the jbyteArray to UTF-8");
    e.printStackTrace();
}

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