Question

请原谅我，因为我对c ++ jni环境不熟悉

我正在尝试将一个String []数组从java传递到JNI桥接到c ++，同时遵循我在这里给出的提示这个片段的提示：

void MyJNIFunction(JNIEnv *env, jobject object, jobjectArray stringArray) {

    int stringCount = env->GetArrayLength(stringArray);

    for (int i=0; i<stringCount; i++) {
        jstring string = (jstring) (env->GetObjectArrayElement(stringArray, i));
        const char *rawString = env->GetStringUTFChars(string, 0);
        // Don't forget to call `ReleaseStringUTFChars` when you're done.
    }
}

我在我的代码中已经尝试了很多方法，但我仍然得到了一个不可挽回的＆＃34;＃34;来自logcat和我的应用停止的错误。请查看我的代码和帮助。非常感谢你。

我的代码：

JNIEXPORT void Java_ran_com_FirstActivity_Example(
        JNIEnv *javaEnvironment, jobject self, jobjectArray stringArray, jlongArray params) {
    // Convert the input jlong array to a regular int array.
    jlong *longParams = javaEnvironment->GetLongArrayElements(params, JNI_FALSE);
    int arr[6];
    for (int n = 0; n < 6; n++) arr[n] = longParams[n];
    javaEnvironment->ReleaseLongArrayElements(params, longParams, JNI_ABORT);


    int stringCount = javaEnvironment->GetArrayLength(stringArray);

    for (int i=0; i<stringCount; i++) {
        jstring string = (jstring) (javaEnvironment->GetObjectArrayElement(stringArray, 2));
        const char *rawString = javaEnvironment->GetStringUTFChars(string, 0);
        // a method I created
        example = new Example(rawString, arr);
        javaEnvironment->ReleaseStringUTFChars(string, rawString);
    }

}

Answer 1

非常感谢timrau让我有信心深入了解我的“jni”代码。我最后通过将字符串提取到字符来解决这个问题，然后再将它们传递给我将使用它们的方法

JNIEXPORT void Java_ran_com_FirstActivity(JNIEnv *javaEnvironment, jobject self, jobjectArray stringArray) {

    int stringCount = javaEnvironment->GetArrayLength(stringArray);

    for (int i=0; i<stringCount; i++) {
            jstring string = (jstring) (javaEnvironment->GetObjectArrayElement(stringArray, 0));
            const char *rawString = javaEnvironment->GetStringUTFChars(string, JNI_FALSE);

            jstring istring = (jstring) (javaEnvironment->GetObjectArrayElement(stringArray, 1));
            const char *rawStringb = javaEnvironment->GetStringUTFChars(istring, JNI_FALSE);
            // I extracyed both string items to different chars before passing //to my methods...since jni only support passing two custom parameters
            example = new SuperpoweredExample(rawString, rawStringb);
            javaEnvironment->ReleaseStringUTFChars(string, rawString);
            javaEnvironment->ReleaseStringUTFChars(istring, rawStringb);
        }

}

Answer 2

int stringCount = javaEnvironment->GetArrayLength(stringArray);

for (int i=0; i<stringCount; i++) {
    jstring string = (jstring) (javaEnvironment->GetObjectArrayElement(stringArray, 2));

您可能确实打算调用以下行来枚举stringArray中的所有字符串。

    jstring string = (jstring)(javaEnvironment->GetObjectArrayElement(stringArray, i);
    //i, not 2

正确的JNI转换从jobjectarray获取数组项到单独的const char

2 个答案: