问题描述
如何使用 jstring (JNI)转换为 std :: string
(c ++) > utf8 个字符?
How to convert jstring
(JNI) to std::string
(c++) with utf8
characters?
这是我的代码。
std::string jstring2string(JNIEnv *env, jstring jStr){
const char *cstr = env->GetStringUTFChars(jStr, NULL);
std::string str = std::string(cstr);
env->ReleaseStringUTFChars(jStr, str);
return str;
}
推荐答案
经过很多时间后才找到解。我找到了一种方法:
After a lot time to find solution. i was found a way:
在Java中,Unicode字符将使用2个字节( utf16
)进行编码。因此 jstring
将包含字符 utf16
。 c ++中的 std :: string
本质上是一个字节字符串,而不是字符,因此,如果我们要从中传递 jstring
JNI
到 c ++
,我们已经将 utf16
转换为字节。
In java, a unicode char will be encoded using 2 bytes (utf16
). so jstring
will container characters utf16
. std::string
in c++ is essentially a string of bytes, not characters, so if we want to pass jstring
from JNI
to c++
, we have convert utf16
to bytes.
在文档,我们有2个函数可从jstring中获取字符串:
in document JNI functions, we have 2 functions to get string from jstring:
// Returns a pointer to the array of Unicode characters of the string.
// This pointer is valid until ReleaseStringchars() is called.
const jchar * GetStringChars(JNIEnv *env, jstring string, jboolean *isCopy);
// Returns a pointer to an array of bytes representing the string
// in modified UTF-8 encoding. This array is valid until it is released
// by ReleaseStringUTFChars().
const char * GetStringUTFChars(JNIEnv *env, jstring string, jboolean *isCopy);
GetStringUTFChars
,它将返回。
GetStringChars
将返回jbyte *,我们将从jbytes中读取char代码并将其转换为c ++中的char
GetStringChars
will return jbyte *, we will read char code from jbytes and convert it to char in c++
this是我的解决方案(与 ascii
和 utf8
字符配合良好):
this is my solution (worked well with ascii
and utf8
characters):
std::string jstring2string(JNIEnv *env, jstring jStr) {
if (!jStr)
return "";
const jclass stringClass = env->GetObjectClass(jStr);
const jmethodID getBytes = env->GetMethodID(stringClass, "getBytes", "(Ljava/lang/String;)[B");
const jbyteArray stringJbytes = (jbyteArray) env->CallObjectMethod(jStr, getBytes, env->NewStringUTF("UTF-8"));
size_t length = (size_t) env->GetArrayLength(stringJbytes);
jbyte* pBytes = env->GetByteArrayElements(stringJbytes, NULL);
std::string ret = std::string((char *)pBytes, length);
env->ReleaseByteArrayElements(stringJbytes, pBytes, JNI_ABORT);
env->DeleteLocalRef(stringJbytes);
env->DeleteLocalRef(stringClass);
return ret;
}
这篇关于从utf8字符将jstring(JNI)转换为std :: string(c ++)的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!