问题描述

我试图将字符阵列从爪哇传递到c.我已经搜索了实施它的方法.但是，当我尝试访问数组的值时，值不正确.

实际上，我试图给数组一个角色.就像buffer[i]=’z’一样，结果在Android中是正确的.

btw，我想要的值是RS232发送的值. RS232的值还可以.

有人告诉我使用bytearray.它可以工作吗?我担心RS232的价值无法存储到bytearray中.

Java

public native int OpenPort(int portnum,int brates);
public native int ClosePort(int portnum);
public native int READ(char[] databuffer);

public char[] buffer=new char[40];

int i;

for(i=0;i<40;i++)
    buffer[i]='s';  //initialization

OpenPort(16,9600); // A function to open the rs232 port

while (i<1000)
{
    READ(buffer);
    i++;
}

JNI.c

JNIEXPORT jint JNICALL Java_com_example_ndk_Vehicles_READ(JNIEnv *env, jclass
cls,jcharArray databuffer)
{

    char tmp[40];
    jchar *buffer=(*env)->GetCharArrayElements(env,databuffer,0);    memset(tmp,0,sizeof(tmp));
    PollComport(16,tmp,40); //will the problem here ? This function need a unsigned char[]
                            //,but in the c program I wrote , char[] was ok for this.
    memcpy(buffer,tmp,40);

    (*env)->ReleaseCharArrayElements(env, databuffer, buffer, 0);

    return 0;
}

推荐答案

这是一个快速示例

public native int play(String filename_main, String filename_prev, int main_x, int main_y, int main_width, int main_height, int preview_x, int preview_y, int preview_width, int preview_height);

映射到

int play(char* filename_main, char* filename_preview, int main_x, int main_y, int main_width, int main_height, int preview_x, int preview_y, int preview_width, int preview_height)

使用此JNI调用.

JNIEXPORT jint JNICALL Java_com_rtrk_demo_PELib_play(JNIEnv *env, jobject obj, jstring main_video, jstring prev_video, jint main_x, jint main_y, jint main_width, jint main_height, jint prev_x, jint prev_y, jint prev_width, jint prev_height)
{
LOGI("JNICALL - Java_com_rtrk_demo_PELib_play(filename)\n");

const char* utf_main_video = env->GetStringUTFChars(main_video, 0);
const char* utf_prev_video = env->GetStringUTFChars(prev_video, 0);
char* file_main_video = (char*) malloc(strlen(utf_main_video) * sizeof(char) +1);
char* file_prev_video = (char*) malloc(strlen(utf_prev_video) * sizeof(char) +1);
strcpy(file_main_video, utf_main_video);
strcpy(file_prev_video, utf_prev_video);
LOGI("JNICALL - filenames: %s\t%s\n", file_main_video, file_prev_video);
env->ReleaseStringUTFChars(main_video, utf_main_video);
env->ReleaseStringUTFChars(prev_video, utf_prev_video);
LOGI("###JNICALL RET - Java_com_rtrk_demo_PELib_play(%s, %s)\n", file_main_video, file_prev_video);

int retVal = play(file_main_video, file_prev_video, (int)main_x, (int)main_y, (int)main_width, (int)main_height, (int)prev_x, (int)prev_y, (int)prev_width, (int)prev_height);
free(file_main_video);
free(file_prev_video);
return retVal;
}

其他推荐答案

因为允许getChararRayelements()制作Java数组的副本，并将您的指针交给副本.在您的代码中，您将通过Null进行指针到树杆的参数，该论点会告诉您是否制作了副本:

jchar *buffer=(*env)->GetCharArrayElements(env,databuffer,0);

因此，您可能正在操作完成后被丢弃的副本.而不是getChararRayElements()，而是在C ++中的本地阵列上操作并使用SetChararRayregion()复制它们.

以上所述是小编给大家介绍的Android Java JNI和C的Char数组 无法识别数值,希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对77isp云服务器技术网的支持！