19

我们有一个使用文件共享的应用程序。设置了 UIFileSharingEnable 等等,这一切似乎都工作正常,但我正在寻找某种关于何时在 iPhone 端添加/删除文件的通知。任何人都可以建议吗?

提前喝彩。

4

4 回答 4

23

Apple Developer Forums 上的这个线程可能很有趣,其中建议您在其自己的线程中运行kqueue,跟踪应用程序的 Documents 文件夹。

Apple 技术人员在此处跟进了一些示例代码

- (void)kqueueFired
{
    int             kq;
    struct kevent   event;
    struct timespec timeout = { 0, 0 };
    int             eventCount;

    kq = CFFileDescriptorGetNativeDescriptor(self->_kqRef);
    assert(kq >= 0);

    eventCount = kevent(kq, NULL, 0, &event, 1, &timeout);
    assert( (eventCount >= 0) && (eventCount < 2) );

    if (eventCount == 1) {
        NSLog(@"dir changed");
    }    

    CFFileDescriptorEnableCallBacks(self->_kqRef, kCFFileDescriptorReadCallBack);
}

static void KQCallback(CFFileDescriptorRef kqRef, CFOptionFlags callBackTypes, void *info)
{
    ViewController *    obj;

    obj = (ViewController *) info;
    assert([obj isKindOfClass:[ViewController class]]);
    assert(kqRef == obj->_kqRef);
    assert(callBackTypes == kCFFileDescriptorReadCallBack);

    [obj kqueueFired];
}

- (IBAction)testAction:(id)sender
{
    #pragma unused(sender)
    NSString *              docPath;
    int                     dirFD;
    int                     kq;
    int                     retVal;
    struct kevent           eventToAdd;
    CFFileDescriptorContext context = { 0, self, NULL, NULL, NULL };
    CFRunLoopSourceRef      rls;

    docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    assert(docPath != 0);

    NSLog(@"%@", docPath);

    dirFD = open([docPath fileSystemRepresentation], O_EVTONLY);
    assert(dirFD >= 0);

    kq = kqueue();
    assert(kq >= 0);

    eventToAdd.ident  = dirFD;
    eventToAdd.filter = EVFILT_VNODE;
    eventToAdd.flags  = EV_ADD | EV_CLEAR;
    eventToAdd.fflags = NOTE_WRITE;
    eventToAdd.data   = 0;
    eventToAdd.udata  = NULL;

    retVal = kevent(kq, &eventToAdd, 1, NULL, 0, NULL);
    assert(retVal == 0);

    assert(self->_kqRef == NULL);

    self->_kqRef = CFFileDescriptorCreate(NULL, kq, true, KQCallback, &context);
    assert(self->_kqRef != NULL);

    rls = CFFileDescriptorCreateRunLoopSource(NULL, self->_kqRef, 0);
    assert(rls != NULL);

    CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode);

    CFRelease(rls);

    CFFileDescriptorEnableCallBacks(self->_kqRef, kCFFileDescriptorReadCallBack);
}
于 2010-07-06T18:58:39.770 回答
18

这是使用 Grand Central Dispatch (GCD) 的替代解决方案,它允许您从 NSNotificationCenter 接收文件更改通知:

将这些变量添加到类的接口中:

// Dispatch queue
dispatch_queue_t _dispatchQueue;

// A source of potential notifications
dispatch_source_t _source;

将以下代码添加到实现中:

    #define fileChangedNotification @"fileChangedNotification"

    // Get the path to the home directory
    NSString * homeDirectory = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];

    // Create a new file descriptor - we need to convert the NSString to a char * i.e. C style string
    int filedes = open([homeDirectory cStringUsingEncoding:NSASCIIStringEncoding], O_EVTONLY);

    // Create a dispatch queue - when a file changes the event will be sent to this queue
    _dispatchQueue = dispatch_queue_create("FileMonitorQueue", 0);

    // Create a GCD source. This will monitor the file descriptor to see if a write command is detected
    // The following options are available

    /*!
     * @typedef dispatch_source_vnode_flags_t
     * Type of dispatch_source_vnode flags
     *
     * @constant DISPATCH_VNODE_DELETE
     * The filesystem object was deleted from the namespace.
     *
     * @constant DISPATCH_VNODE_WRITE
     * The filesystem object data changed.
     *
     * @constant DISPATCH_VNODE_EXTEND
     * The filesystem object changed in size.
     *
     * @constant DISPATCH_VNODE_ATTRIB
     * The filesystem object metadata changed.
     *
     * @constant DISPATCH_VNODE_LINK
     * The filesystem object link count changed.
     *
     * @constant DISPATCH_VNODE_RENAME
     * The filesystem object was renamed in the namespace.
     *
     * @constant DISPATCH_VNODE_REVOKE
     * The filesystem object was revoked.
     */

    // Write covers - adding a file, renaming a file and deleting a file...
    _source = dispatch_source_create(DISPATCH_SOURCE_TYPE_VNODE,filedes,
                                                       DISPATCH_VNODE_WRITE,
                                                       _dispatchQueue);


    // This block will be called when teh file changes
    dispatch_source_set_event_handler(_source, ^(){
        // We call an NSNotification so the file can change can be detected anywhere
        [[NSNotificationCenter defaultCenter] postNotificationName:fileChangedNotification object:Nil];
    });

    // When we stop monitoring the file this will be called and it will close the file descriptor
    dispatch_source_set_cancel_handler(_source, ^() {
        close(filedes);
    });

    // Start monitoring the file...
    dispatch_resume(_source);

    //...

    // When we want to stop monitoring the file we call this
    //dispatch_source_cancel(source);


    // To recieve a notification about the file change we can use the NSNotificationCenter
    [[NSNotificationCenter defaultCenter] addObserverForName:fileChangedNotification object:Nil queue:Nil usingBlock:^(NSNotification * notification) {
        NSLog(@"File change detected!");
    }];
于 2013-12-06T12:02:55.657 回答
4

老问题,但我遇到了这个包含目录监视器的Apple 代码。请注意,它会在添加(或删除)文件时触发;这可能是在操作系统完成写入文件之前。

于 2012-10-06T13:18:22.397 回答
0

我刚刚实现了这个

它使用 GCD 框架,就像上面 @James 的答案一样,包装在一个组合发布者中,从而产生更简单的客户端代码。

示例用法:

let id = UUID()
let tmpURL = FileManager.default.temporaryDirectory
let url = URL(fileURLWithPath: "\(id)", relativeTo: tmpURL)
let tmp = try! FileDescriptor.open(tmpURL.path, .readOnly, options: .eventOnly)

var received = DispatchSource.FileSystemEvent()

print(received)     // prints "FileSystemEvent(rawValue: 0)"

let cancellable = DispatchSource.publish(at: tmp)
  .sink { event in
    received = event
  }

try! FileManager.default.createDirectory(at: url, withIntermediateDirectories: false, attributes: nil)
    
sleep(1)

print(received)     // prints "FileSystemEvent(rawValue: 18)"

cancellable.cancel()
于 2022-01-07T12:06:42.683 回答