Java 泛型 -- 不兼容的类型 Required:java.io.filedescriptor Found:java.lang.object

Question

我使用 JNI 调用 c 函数来创建接口。我在 android studio

上收到以下错误消息

不兼容的类型
要求：java.io.FileDescriptor
找到：java.lang.Object

packet.java

FileDescriptor myDev= null;
myDev = JNI.prepare_fd("/dev/net/tun", myDev); =>this line hava above error
in2 = new FileInputStream(myDev);

JNI.java

    public class JNI {
           static {
                     System.loadLibrary("JNITest");
           }
           public static native Object prepare_fd(String filename, FileDescriptor fdobj);
   }

packet_JNI.h

JNIEXPORT jobject JNICALL Java_com_example_packetcapture_JNI_prepare_fd (JNIEnv *, jclass, jstring );

JNITest.c

    JNIEXPORT jobject JNICALL
    Java_com_example_packetcapture_JNI_prepare_1fd(JNIEnv *env, jclass _ignore, jstring filename)
    { 
    jfieldID field_fd;
    jmethodID const_fdesc;
    jclass class_fdesc, class_ioex;
    jobject ret;
    int fd;
    char *fname;

    class_ioex = (*env)->FindClass(env, "java/io/IOException");
    if (class_ioex == NULL) return NULL;
    class_fdesc = (*env)->FindClass(env, "java/io/FileDescriptor");
    if (class_fdesc == NULL) return NULL;

    fname = (*env)->GetStringUTFChars(env, filename, NULL);

    fd = open(fname, O_RDWR | O_NONBLOCK);

    (*env)->ReleaseStringUTFChars(env, filename, fname);

    if (fd < 0) {
        // open returned an error. Throw an IOException with the error string
        char buf[1024];
        sprintf(buf, "open: %s", strerror(errno));
        (*env)->ThrowNew(env, class_ioex, buf);
        return NULL;
    }

    // construct a new FileDescriptor
    const_fdesc = (*env)->GetMethodID(env, class_fdesc, "<init>", "()V");
    if (const_fdesc == NULL) return NULL;
    ret = (*env)->NewObject(env, class_fdesc, const_fdesc);

    // poke the "fd" field with the file descriptor
    field_fd = (*env)->GetFieldID(env, class_fdesc, "fd", "I");
    if (field_fd == NULL) return NULL;
    (*env)->SetIntField(env, ret, field_fd, fd);

    // and return it
    return ret;
    }

谁能告诉我一些想法？如何修复此错误。谢谢。

Answer 1

下一行表明它是一个通用对象类型：

public static native Object prepare_fd(String filename, FileDescriptor fdobj);

最简单的解决方法是在设置 myDev 时将其转换为文件描述符：

myDev = (filedescriptor) JNI.prepare_fd("/dev/net/tun", myDev);

Java 泛型 -- 不兼容的类型 Required:java.io.filedescriptor Found:java.lang.object

Java Generics-- Incompatible types Required:java.io.filedescriptor Found:java.lang.object

java

java-native-interface

android

android-ndk