jni的jstring转为char指针和jni中使用logcat

• jni的jstring转为char指针

  #include <jni.h>
  #include <stdlib.h>
  #include <android/log.h>
  #define LOG_TAG "System.out"
  #define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
  /**
   * 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 > 0) {
              rtn = (char*)malloc(alen+1); //"\0"
              memcpy(rtn, ba, alen);
              rtn[alen]=0;
        }
        (*env)->ReleaseByteArrayElements(env, barr, ba,0);
        return rtn;
  }