将某些内容添加到 NSPasteboard 时收到通知答案

【问题标题】：Get notified when something is added to NSPasteboard将某些内容添加到 NSPasteboard 时收到通知
【发布时间】：2015-06-20 15:45:47
【问题描述】：

在我的应用程序中，如果将某些内容添加到 NSPasteboard 中，我希望得到通知。如果我从任何其他程序复制文本，我希望我的应用程序知道它。

在某处我读到它不能那样做。我应该创建一个计时器并自己检查 NSPasteboard 的内容。

这是这样做的吗？或者有什么通知？

【问题讨论】：

标签： objective-c cocoa

【解决方案1】：

是的，您基本上必须轮询粘贴板以查看其内容是否已更改。这并不理想，但有可能。基本上，您有一个每秒触发一次或两次并检查-[NSPasteboard changeCount] 的计时器。如果changeCount 发生变化，则意味着粘贴板的内容也发生了变化（或者至少有一个新所有者）。

【讨论】：

啊，我打字的时候抓到我了...好吧，要添加到帖子中，您可以设置一些类似这样的代码 (pastie.org/1129293) 以观察变化。

【解决方案2】：

根据 Dave DeLong 提供的答案，我想出了类似的实现，但很快，这里是其要点的链接：PasteboardWatcher.swift

代码 sn-p 来自同一：

class PasteboardWatcher : NSObject {

    // assigning a pasteboard object
    private let pasteboard = NSPasteboard.generalPasteboard()

    // to keep track of count of objects currently copied
    // also helps in determining if a new object is copied
    private var changeCount : Int

    // used to perform polling to identify if url with desired kind is copied
    private var timer: NSTimer?

    // the delegate which will be notified when desired link is copied
    var delegate: PasteboardWatcherDelegate?

    // the kinds of files for which if url is copied the delegate is notified
    private let fileKinds : [String]

    /// initializer which should be used to initialize object of this class
    /// - Parameter fileKinds: an array containing the desired file kinds
    init(fileKinds: [String]) {
        // assigning current pasteboard changeCount so that it can be compared later to identify changes
        changeCount = pasteboard.changeCount

        // assigning passed desired file kinds to respective instance variable
        self.fileKinds = fileKinds

        super.init()
    }
    /// starts polling to identify if url with desired kind is copied
    /// - Note: uses an NSTimer for polling
    func startPolling () {
        // setup and start of timer
        timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("checkForChangesInPasteboard"), userInfo: nil, repeats: true)
    }

    /// method invoked continuously by timer
    /// - Note: To keep this method as private I referred this answer at stackoverflow - [Swift - NSTimer does not invoke a private func as selector](http://stackoverflow.com/a/30947182/217586)
    @objc private func checkForChangesInPasteboard() {
        // check if there is any new item copied
        // also check if kind of copied item is string
        if let copiedString = pasteboard.stringForType(NSPasteboardTypeString) where pasteboard.changeCount != changeCount {

            // obtain url from copied link if its path extension is one of the desired extensions
            if let fileUrl = NSURL(string: copiedString) where self.fileKinds.contains(fileUrl.pathExtension!){

                // invoke appropriate method on delegate
                self.delegate?.newlyCopiedUrlObtained(copiedUrl: fileUrl)
            }

            // assign new change count to instance variable for later comparison
            changeCount = pasteboard.changeCount
        }
    }
}

注意： 在共享代码中，我试图确定用户是否复制了文件 url 与否，提供的代码可以很容易地修改为其他一般目的。

【讨论】：