/**

 * 把一个jstring转换成一个c语言的char* 类型.

 */

char* _JString2CStr(JNIEnv* env, jstring jstr) {

    char* rtn = NULL;

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

    jstring strencode = (*env)->NewStringUTF(env, "GB2312");

    jmethodID mid = (*env)->GetMethodID(env, clsstring, "getBytes",

            "(Ljava/lang/String;)[B");

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

            strencode); // String .getByte("GB2312");

    jsize alen = (*env)->GetArrayLength(env, barr);

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

    if (alen > ) {

        rtn = (char*) malloc(alen + ); //"\0"

        memcpy(rtn, ba, alen);

        rtn[alen] = ;

    }

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

    return rtn;

}

/*

 * Class:     com_wuyudong_javapassdata_JNI

 * Method:    sayHelloInC

 * Signature: (Ljava/lang/String;)Ljava/lang/String;

 */
JNIEXPORT jstring JNICALL Java_com_wuyudong_javapassdata_JNI_sayHelloInC(

        JNIEnv * env, jobject clazz, jstring jstr) {

    //调用工具方法把java中的string类型转换成C语言中的char×

    char* cstr = _JString2CStr(env, jstr);

    int len = strlen(cstr);

    int i;

    for (i = ; i < len; i++) {

        *(cstr + i) += ;

    }

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

}

    public void passString(View v) {

        Toast.makeText(getApplicationContext(), jni.sayHelloInC("hello yudong"), 0).show();

    }