记录下JNI常用类型转换:
string转jstring
std::string hello = "Hello from C++";
jstring jHello=env->NewStringUTF(hello.c_str());
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char*转jstring
jstring util_char_to_jstring(JNIEnv *env, const char *pat) {
//定义java String类 strClass
jclass strClass = (env)->FindClass("java/lang/String");
//获取String(byte[],String)的构造器,用于将本地byte[]数组转换为一个新String
jmethodID ctorID = (env)->GetMethodID(strClass, "<init>", "([BLjava/lang/String;)V");
//建立byte数组
jbyteArray bytes = (env)->NewByteArray(strlen(pat));
//将char* 转换为byte数组
(env)->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte *) pat);
// 设置String, 保存语言类型,用于byte数组转换至String时的参数
jstring encoding = (env)->NewStringUTF("utf-8");
//将byte数组转换为java String,并输出
return (jstring) (env)->NewObject(strClass, ctorID, bytes, encoding);
}
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jstring转char*:
void util_jstring_to_char(JNIEnv *env, jstring jstr, char *result) {
if (env == NULL || jstr == NULL) {
return;
}
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) {
memcpy(result, ba, alen);
result[alen] = 0;
}
env->ReleaseByteArrayElements(barr, ba, 0);
}
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而char*
是可以直接赋值给string
的:
string s;
char *p = "hello";//直接赋值
s = p;
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int转string
string util_int_to_string(unsigned int n) {
string sResult;
stringstream ssTmp;
ssTmp << n;
ssTmp >> sResult;
return sResult;
}
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JByteArray转char*
char *convertJByteArrayToChar(JNIEnv *env, jbyteArray byYUV1_) {
jbyte *bytes = env->GetByteArrayElements(byYUV1_, 0);
int arrayLength = env->GetArrayLength(byYUV1_);
char *chars = new char[arrayLength + 1];
memset(chars, 0x0, arrayLength + 1);
memcpy(chars, bytes, arrayLength);
chars[arrayLength] = 0;
env->ReleaseByteArrayElements(byYUV1_, bytes, 0);
return chars;
}
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char*转JByteArray
jbyteArray util_char_to_jbyteArray(JNIEnv *env, char *data, int length) {
jbyte *by = (jbyte *) data;
jbyteArray jarray = env->NewByteArray(length);
env->SetByteArrayRegion(jarray, 0, length, by);
return jarray;
}
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