JNI与C/C++数据类型的转换

字符数组与jbyteArray

jbyteArray转字符数组

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int byteSize = (int) env->GetArrayLength(jbyteArrayData); //jbyteArrayData是jbyteArray类型的数据 unsigned char* data = new unsigned char[byteSize + 1]; env->GetByteArrayRegion(jbyteArrayData, 0, byteSize, reinterpret_cast(data)); data[byteSize] = '\0';

字符数组转jbyteArray

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jbyte *jb = (jbyte*) data; //data是字符数组类型 jbyteArray jarray = env->NewByteArray(byteSize); //byteSize是字符数组大小 env->SetByteArrayRegion(jarray, 0, byteSize, jb);

字符数组与jstring

jstring转字符数组

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char* JstringToChar(JNIEnv* env, jstring jstr) { if(jstr == NULL) { return NULL; } 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; }

字符数组转jstring

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jstring StrtoJstring(JNIEnv* env, const char* pat) { jclass strClass = env->FindClass("java/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); }

或者直接使用NewStringUTF方法：

1	jstring jstr = env->NewStringUTF(str);

int与jint

jint与int的互转都可以直接使用强转，如：

1	jint i = (jint) 10;