java向 jni传递问文件指针

1、创建 fd ，jni 接口

public  static native int openFileFromNative(FileDescriptor fileDescriptor);

2、java 文件获取文件指针

ParcelFileDescriptor pfd =  = getContentResolver().openFileDescriptor(filePathUri, "rw");
      FileDescriptor fd = pfd.getFileDescriptor();
      openFileFromNative(fd);

3、C++ 调用函数

static int jniGetFDFromFileDescriptor(JNIEnv * env, jobject fileDescriptor) {
    jint fd = -1;
    jclass fdClass = env->FindClass("java/io/FileDescriptor");
    if (fdClass != NULL) {
        jfieldID fdClassDescriptorFieldID = env->GetFieldID(fdClass, "descriptor", "I");
        if (fdClassDescriptorFieldID != NULL && fileDescriptor != NULL) {
            fd = env->GetIntField(fileDescriptor, fdClassDescriptorFieldID);
        }
    }
    LOGD("jni Get FD From File Descriptor %d",fd);
    return fd;
}

// jni对应函数
static jint openFileFromNative(JNIEnv* env, jobject clazz,  jobject fileDescriptor) {
 int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
 //todo
}

文章参考：
如何正确通过在Android中使用JNI资产的FileDescriptor到FFmpeg的(How to properly pass an asset FileDescriptor to FFmpeg using JNI in Android)