NewObject的上呼叫无效的间接引用

问题描述

好了，我有天然code以下。我试图返回FilePermissionInfo从一个数组，填充（）由stat返回的一些数据。问题是，我得到以下错误，当被NewObject的第一次调用：

OK, so I have the native code below.I'm trying to return an array of FilePermissionInfo from it, populated with some data returned by stat().The problem is that I get the following error when NewObject is called the first time:

06-15 20：25：17.621：W / dalvikvm（2287）：无效的间接引用  0x40005820在德codeIndirectRef 06-15 20：25：17.621：E / dalvikvm（2287）：  VM终止执行

这是奇怪的，因为只有参考对象我是JC​​LASS（对于FilePermissionInfo），我把它转化为一个全球性的参考。

It's odd, because the only reference object I have is the jclass (for FilePermissionInfo) and I turn it to a global reference.

在code是：

JNIEXPORT jobjectArray JNICALL
Java_com_mn_rootscape_utils_NativeMethods_getFilesPermissions( JNIEnv* env, jobject thizz, jobjectArray filePathsArray )
{
jobjectArray result;
int size = (*env)->GetArrayLength(env, filePathsArray);
jboolean isCopy;

jclass filePermInfoCls = (*env)->FindClass(env, kFilePermissionInfoPath);
if(!filePermInfoCls)
{
    LOGE("getFilesPermissions: failed to get class reference.");
    return NULL;
}

gFilePermInfoClass = (jclass)(*env)->NewGlobalRef(env, filePermInfoCls);
LOGI("got gFilePermInfoClass");

jmethodID filePermInfoClsConstructor = (*env)->GetMethodID(env, gFilePermInfoClass, "<init>", kFilePermInfoConstructorSig);
if(!filePermInfoClsConstructor)
{
    LOGE("getFilesPermissions: failed to get method reference.");
    return NULL;
}

struct stat sb;

LOGI("starting...");
result = (jobjectArray)(*env)->NewObjectArray(env, size, gFilePermInfoClass, NULL);
for(int i = 0; i != size; ++i)
{
    jstring string = (jstring) (*env)->GetObjectArrayElement(env, filePathsArray, i);
const char *rawString = (*env)->GetStringUTFChars(env, string, &isCopy);

    if(stat(rawString, &sb) == -1)
    {
        LOGE("stat error for: %s", rawString);
    }

    LOGI("%ld %ld %ld %ld %ld %ld %ld %ld", sb.st_dev, sb.st_mode, sb.st_nlink, sb.st_uid, sb.st_gid, sb.st_atime, sb.st_mtime, sb.st_ctime);

    jobject permInfo = (*env)->NewObject(env,
                            gFilePermInfoClass,
                            filePermInfoClsConstructor,
                            (long)sb.st_dev,
                            (long)sb.st_mode,
                            (long)sb.st_nlink,
                            (long)sb.st_uid,
                            (long)sb.st_gid,
                            (long)sb.st_atime,
                            (long)sb.st_mtime,
                            (long)sb.st_ctime,
                            "",
                            "",
                            1,
                            "");

    LOGI("xxx1");
    (*env)->SetObjectArrayElement(env, result, i, permInfo);
    LOGI("xxx2");
    (*env)->ReleaseStringUTFChars(env, string, rawString);
    LOGI("xxx3");
}

(*env)->DeleteLocalRef(env, filePermInfoCls);

return result;

}

Java类的构造函数签名和路径是：

The Java class constructor signature and path are:

const char* kFilePermissionInfoPath = "com/mn/rootscape/utils/FilePermissionInfo";
const char* kFilePermInfoConstructorSig = "(JJJJJJJJLjava/lang/String;Ljava/lang/String;ZLjava/lang/String;)V";

请注意，如果我叫上NewObject的默认构造函数那么它工作正常。

Please note that if I call NewObject on the default constructor then it works fine.

推荐答案

好了，找到了。正是有了的jstring 参数有问题。事实证明，你不能将空字符串（甚至NULL为此事）作为的jstring 。相反，我用（* ENV） - ＆GT; NewStringUTF（ENV，NULL）以创建一个空的jstring 。

OK, found it.It was a problem with the jstring parameters. It turns out you cannot pass empty strings (or even NULL for that matter) as a jstring.Instead I used (*env)->NewStringUTF(env, NULL) to create a NULL jstring.

似乎现在的工作确定。

由于这个问题产生的有点高活性，我张贴下面的最终解决方案。请注意， nullString 变量被释放在其范围结束（或当您使用它做）：

Since this question generated somewhat a high activity, I'm posting the final solution below. Note that the nullString variable is being deallocated at the end of its scope (or when you're done using it):

        jstring nullString = (*env)->NewStringUTF(env, NULL);
...
        jobject permInfo = (*env)->NewObject(env,
                                gFilePermInfoClass,
                                filePermInfoClsConstructor,
                                (jbyte)permsOwner,
                                (jbyte)permsGroup,
                                (jbyte)permsOthers,
                                (jlong)sb.st_uid,
                                (jlong)sb.st_gid,
                                (jlong)sb.st_atime,
                                (jlong)sb.st_mtime,
                                (jlong)sb.st_ctime,
                                nullString,
                                nullString,
                                (jboolean)1,
                                nullString);
...
       (*env)->DeleteLocalRef(env, nullString);

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