jni和java之间字符串的转换

 jni和java之间字符串的转换方法。

　　C的实现:

　　JNIEXPORT jstring JNICALL Java_Android123_CwjC (JNIEnv *env, jobject obj, jstring string)

　　{

　　　char szBuffer[255];

　　　return (*env)->NewStringUTF(env, szBuffer);

　　}

　　C++的实现:

　　JNIEXPORT jstring JNICALL Java_Android123_CwjCpp (JNIEnv *env, jobject obj, jstring string)

　　{

　　const char *strUTF = env->GetStringUTFChars(string, 0);

　　char szBuffer[255];

　　strcpy(szBuffer, strUTF);

　　env->ReleaseStringUTFChars(string, strUTF);

　　return env->NewStringUTF(szBuffer);

　　}

java中string与byte[]的转换  

1.string 转 byte[]

byte[] midbytes=isoString.getBytes("UTF8");

//为UTF8编码

byte[] isoret = srt2.getBytes("ISO-8859-1");

//为ISO-8859-1编码

其中ISO-8859-1为单字节的编码

2.byte[]转string

String isoString = new String(bytes,"ISO-8859-1");

String srt2=new String(midbytes,"UTF-8");

 

//jbytearray转c++byte数组

jbyte * arrayBody = env->GetByteArrayElements(data,0);

3

jsize theArrayLengthJ = env->GetArrayLength(data);

4

BYTE * starter = (BYTE *)arrayBody;

 

1

//jbyteArray 转 c++中的BYTE[]

//jbytearray array

jbyte * olddata = (jbyte*)env->GetByteArrayElements(array, 0);

jsize  oldsize = env->GetArrayLength(array);

BYTE* bytearr = (BYTE*)olddata;

int len = (int)oldsize;

//C++中的BYTE[]转jbyteArray

//nOutSize是BYTE数组的长度 BYTE pData[]

jbyte *by = (jbyte*)pData;

jbyteArray jarray = env->NewByteArray(nOutSize);

env->SetByteArrayRegin(jarray, 0, nOutSize, by);

//jbyteArray 转 char *

char* data = (char*)env->GetByteArrayElements(strIn, 0);

//char* 转jstring

jstring WindowsTojstring(JNIEnv* env, char* str_tmp)

{

    jstring rtn=0;

    int slen = (int)strlen(str_tmp);

    unsigned short* buffer=0;

    if(slen == 0)

    {

        rtn = env->NewStringUTF(str_tmp);

    }

11

    else

    {

        int length = MultiByteToWideChar(CP_ACP, 0, (LPCSTR)str_tmp, slen, NULL, 0);

        buffer = (unsigned short*)malloc(length*2+1);

        if(MultiByteToWideChar(CP_ACP, 0, (LPCSTR)str_tmp, slen, (LPWSTR)buffer, length) > 0)

        {

            rtn = env->NewString((jchar*)buffer, length);

        }

    }

    if(buffer)

 {

     free(buffer);

 }

 return rtn;

}

 

1

//jstring 转 char* 或者 const char*

// jstring str

const char *key = env->GetStringUTFChars(str, 0);

//jboolean isOffer

jsClient->modify(key, isOffer);

//需要释放，否则容易内存泄露

env->ReleaseStringUTFChars(str, key);

//JNI 返回 jbyteArray

JNIEXPORT jbyteArray JNICALL Java_Test_getByteArray(JNIEnv *env, jobject obj)

{

    jbyteArray firstMacArray = env->NewByteArray( 6 );

    jbyte *bytes = env->GetByteArrayElements( firstMacArray, 0);

    for ( int i = 0; i < sizeof( pAdapterInfo->Address ); i++ )

{

       bytes[ i ] = pAdapterInfo->Address[ i ];

}

    env->SetByteArrayRegion(firstMacArray, 0, 6, bytes );

    return firstMacArray;

}

//jstring to char*

char* jstringTostring(JNIEnv* env, jstring jstr)

{       

    char* rtn = NULL;

    jclass clsstring = env->FindClass("java/lang/String");

    jstring strencode = env->NewStringUTF("utf-8");

    jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");

    jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);

    jsize alen = env->GetArrayLength(barr);

    jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);

    if (alen > 0)

{

        rtn = (char*)malloc(alen + 1);

        memcpy(rtn, ba, alen);

        rtn[alen] = 0;

    }

    env->ReleaseByteArrayElements(barr, ba, 0);

    return rtn;

}

char* to jstring

jstring stoJstring(JNIEnv* env, const char* pat)

{

    jclass strClass = env->FindClass("Ljava/lang/String;");

    jmethodID ctorID = env->GetMethodID(strClass, "", "([BLjava/lang/String;)V");

    jbyteArray bytes = env->NewByteArray(strlen(pat));

    env->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat);

    jstring encoding = env->NewStringUTF("utf-8");

    return (jstring)env->NewObject(strClass, ctorID, bytes, encoding);

}

//将jstring类型转换成windows类型

char* jstringToWindows( JNIEnv *env, jstring jstr )

{

    int length = (env)->GetStringLength(jstr );

  const jchar* jcstr = (env)->GetStringChars(jstr, 0 );

  char* rtn = (char*)malloc( length*2+1 );

  int size = 0;

  size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr, length, rtn,(length*2+1), NULL, NULL );

    if( size <= 0 )

return NULL;

(env)->ReleaseStringChars(jstr, jcstr );

rtn[size] = 0;

return rtn;

}

//将windows类型转换成jstring类型

jstring WindowsTojstring( JNIEnv* env, char* str )

{

    jstring rtn = 0;

    int slen = strlen(str);

    unsigned short * buffer = 0;

    if( slen == 0 )

        rtn = (env)->NewStringUTF(str );

    else

    {

        int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, NULL, 0 );

        buffer = (unsigned short *)malloc( length*2 + 1 );

        if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, (LPWSTR)buffer, length ) >0 )

            rtn = (env)->NewString( (jchar*)buffer, length );

    }

    if( buffer )

        free( buffer );

    return rtn;

}

//从传进来的对象中取出byte[]

jfieldID byteData = (env)->GetFieldID(clazz,"bData","[B");

jbyteArray pDataIn = (jbyteArray) (env)->GetObjectField(objDataIn, byteData);

jsize theArrayLeng = env->GetArrayLength(pDataIn);

//byte[]转为BYTE[]

jbyte * arrayBody = env->GetByteArrayElements(pDataIn,0);

BYTE * jDataIn = (BYTE *)arrayBody;

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//将BYTE数组转为jarray

jbyte* byte = (jbyte*)jDataOut;   

jbyteArray jarray = env->NewByteArray(theArrayLeng);

env->SetByteArrayRegion(jarray, 0, theArrayLeng, byte);

//给每一个实例的变量付值

(env)->SetObjectField(objDataIn,byteData,jarray);

(env)->SetIntField(objDataIn,pDataInLen,jDataInLen);

(env)->ReleaseByteArrayElements(pDataIn, arrayBody, 0);

文章来源: blog.csdn.net，作者：网奇，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/jacke121/article/details/61419570