Java native 接口(interface) GetStringUTFChars fatal error

Question

我有一个名为“Robotic Arm Edge”的机器人和 USB 接口(interface)。我正在尝试制作自定义软件，但这涉及到 Java native 接口(interface)。我选择 Java 是因为它比用于 C/C++ 的 ATK+ 库更容易制作 gui 界面。我需要 Java Native 接口(interface)的原因是 libusb，我已经有一个我自己编写的工作 Controller 。现在，我需要做的就是编写一个 Java 包装器，但我需要将 jstring 转换为 c 字符串。 GetStringUTFChars JNI 方法总是导致 fatal error ，我已经尝试了几乎所有可能的方法变体。这是 Java 类:

RoboController.java:

package arm.robot;

import arm.robot.enums.*;


public class RoboController {


    static {
        System.loadLibrary("robojava");
        sendToRobo0("");
    }

    static Pinchers m1 = Pinchers.stopped;
    static Joint    m2 = Joint.stopped;
    static Joint    m3 = Joint.stopped;
    static Joint    m4 = Joint.stopped;
    static Base     m5 = Base.stopped;
    static Light    l  = Light.off;

    private static native boolean sendToRobo0(String cmds);

    public static void sendToRobo(){
        StringBuilder sb = new StringBuilder("");
        boolean first = true;

        if(m1.equals(Pinchers.opening)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m1o");
        }
        else if(m1.equals(Pinchers.closing)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m1c");
        }

        if(m2.equals(Joint.up)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m2u");
        }
        else if(m2.equals(Joint.down)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m2d");
        }

        if(m3.equals(Joint.up)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m3u");
        }
        else if(m3.equals(Joint.down)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m3d");
        }

        if(m4.equals(Joint.up)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m4u");
        }
        else if(m4.equals(Joint.down)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m4d");
        }

        if(m5.equals(Base.clockwise)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m5cw");
        }
        else if(m5.equals(Base.counterclockwise)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("m5ccw");
        }

        if(l.equals(Light.on)) {
            if(!first){
                sb.append(" ");
            }
            else first = false;
            sb.append("lon");
        }
        sendToRobo0(sb.toString());
    }
}

来自 javah 的 header :

arm_robot_RoboController.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class arm_robot_RoboController */

#ifndef _Included_arm_robot_RoboController
#define _Included_arm_robot_RoboController
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     arm_robot_RoboController
 * Method:    sendToRobo0
 * Signature: (Ljava/lang/String;)Z
 */
JNIEXPORT jboolean JNICALL Java_arm_robot_RoboController_sendToRobo0
  (JNIEnv *, jclass, jstring);

#ifdef __cplusplus
}
#endif
#endif

最后是发生 fatal error 的实现:

arm_robot_RoboController.cpp

#include <jni.h>
#include <string>
#include <iostream>
#include "arm_robot_RoboController.h"

using namespace std;


JNIEXPORT jboolean JNICALL Java_arm_robot_RoboController_sendToRobo0(JNIEnv* env, jclass c, jstring args){
    const char *str= env->GetStringUTFChars(args,(jboolean*)0); //FATAL ERROR HERE
    //string s(str);
    //cout << s;
    return true;
}

错误日志:

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0xb676a978, pid=2912, tid=2842113136
#
# JRE version: Java(TM) SE Runtime Environment (7.0_40-b43) (build 1.7.0_40-b43)
# Java VM: Java HotSpot(TM) Client VM (24.0-b56 mixed mode linux-arm )
# Problematic frame:
# V  [libjvm.so+0x262978]  jni_GetStringUTFChars+0x74
#
# Core dump written. Default location: /home/pi/robotic arm/gui/core or core.2912
#
# An error report file with more information is saved as:
# /home/pi/robotic arm/gui/hs_err_pid2912.log
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.sun.com/bugreport/crash.jsp
#
Aborted (core dumped)

我使用的构建命令行:

g++ -c -I"/usr/lib/jvm/jdk-7-oracle-armhf/include" -I"/usr/lib/jvm/jdk-7-oracle-armhf/include/linux" robo.cpp
g++ -I"/usr/lib/jvm/jdk-7-oracle-armhf/include" -I"/usr/lib/jvm/jdk-7-oracle-armhf/include/linux" -olibrobojava.so -shared -Wl,-soname,robojava.so arm_robot_RoboController.cpp robo.o

我使用的是运行接近最新 Raspbian Wheezy 的 Raspberry Pi Model B。我无法找出我做错了什么。

Answer 1

正如在 EJP 评论中一样，我之前的建议是由于缺少 &isCopy 而导致错误，我只留下 ReleaseStringUTFChars 部分。我只能建议在看起来可疑的调用之前和之后添加日志记录，你也应该查看 logcat，当 native 代码中的 jni 发生错误时，android 有时会在那里输出提示。

---

你还必须调用:

ReleaseStringUTFChars

使用str后