Java 调 C 中遇到的字符串转换

（1）java 中的String(jstring) 转换成C的 char * 类型 ：

JNIEXPORT jint JNICALL Java_com_example_libdemo_类名_Init  (JNIEnv *jenv, jclass jc, jstring jdevName) {char* devName = (char *)(jenv->GetStringUTFChars(jdevName, 0));chargDevName2[128] = {0};strcpy(gDevName2, devName);jenv->ReleaseStringUTFChars(jdevName, devName);return 0;}

（2）C的unsigned char转换成Java的jbyteArray类型：

JNIEXPORT jbyteArray JNICALL Java_com_example_libdemo_类名_func  (JNIEnv *jenv, jclass jc) {unsigned charres[3074] = {0x10, 0x0a,0x0b,0x0c,0x0e, 0x0f};unsigned intresLen = 6;jbyteArrayjres = NULL;jres =  jenv->NewByteArray(resLen);jenv->SetByteArrayRegion(jres, 0, resLen, (jbyte*)res);return jres;}

（3）java中调用func

byte[] recvData = 类名.func();if (recvData != null){// 在文本框中显示EditText editText3 =(EditText)findViewById(R.id.editText3); editText3.setText(byteArrayToHex(recvData).toCharArray(), 0, byteArrayToHex(recvData).length());}

Java byteArrayToHex实现：

public static String byteArrayToHex(byte[] a) {        StringBuilder sb = new StringBuilder();        for(byte b: a)           sb.append(String.format("%02x", b&0xff));        return sb.toString();   }

C 字符串转成十六进制，例如字符串“0084000008”转换成 十六进制 00 84 00 00 08

static void tohex(char *hh, unsigned char *dd,int len){    int i = 0;    char h1,h2;    unsigned char s1,s2;    for (i=0;i<len;i++){        h1 = hh[2*i];        h2 = hh[2*i+1];        s1 = toupper(h1) - 0x30;        if (s1 > 9) s1 -= 3;        s2 = toupper(h2) - 0x30;        if (s2 > 9) s2 -= 3;        dd[i] = s1*16 + s2;    }}

//用EditText前，请先:import android.widget.EditText;        //获取文本框1的文本        String str1="";        EditText editText1 =(EditText)findViewById(R.id.editText1);        str1=editText1.getText().toString();                //将文本框1的文本赋给文本框2        EditText editText2 =(EditText)findViewById(R.id.editText2);         editText2.setText(str1.toCharArray(), 0, str1.length());