Ios 为什么PDFKit.beginFindStrings的结果为零？

自学新手在这里

我的最终目标：

iOS/Mac应用程序，加载PDF目录，搜索每个PDF的字符串数组，并列出哪些PDF包含哪些字符串

仅对一个PDF进行原型设计时出现问题：

加载选定的PDF，运行

.beginFindStrings（[“and”，“the”]，带有选项：。不区分大小写）

并等待通知

.pdfdocumentdidendfindfind

检查

[PDFSelection]

，我收到了一个令人困惑的零

那不应该。内存显示PDF已加载。我的线程有问题吗？我想我已经遵循了这里的

async

建议：

代码

import UIKit
import MobileCoreServices
import PDFKit

class ViewController: UIViewController, UIDocumentPickerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    var matchesFound: PDFSelection?

    @IBOutlet weak var resultsLabel: UILabel!

    @IBAction func importPDF(_ sender: Any) {
        let picker = UIDocumentPickerViewController(documentTypes: [kUTTypePDF as String], in: .import)
        picker.delegate = self
        picker.allowsMultipleSelection = false
        self.present(picker, animated: true)
    }

    func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
        guard urls.count == 1 else {return}
        let data = try! Data(contentsOf: urls[0])
        let subjectPDF = PDFDocument.init(data: data)
        guard subjectPDF!.isLocked == false else {return}

        subjectPDF!.beginFindStrings(["the", "and"], withOptions: .caseInsensitive)

        NotificationCenter.default.addObserver(self, selector: #selector(onDidFindMatch(_:)), name: Notification.Name.PDFDocumentDidEndFind, object: nil)
    }

    @objc func onDidFindMatch(_ notification: Notification) {
        resultsLabel.text = "\(String(describing: matchesFound?.string))"
    }

    func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
            dismiss(animated: true, completion: nil)
    }

}

带标记的代码

import UIKit
import MobileCoreServices
import PDFKit

class ViewController: UIViewController, UIDocumentPickerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

//Array of PDFSelection search results
    var matchesFound: PDFSelection?

//Temporary display for search result strings
    @IBOutlet weak var resultsLabel: UILabel!

//Choose a PDF to import, temporarily limited to one
    @IBAction func importPDF(_ sender: Any) {
        let picker = UIDocumentPickerViewController(documentTypes: [kUTTypePDF as String], in: .import)
        picker.delegate = self
        picker.allowsMultipleSelection = false
        self.present(picker, animated: true)
    }

//Load the picked PDF as subjectPDF, if unlocked
    func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
        guard urls.count == 1 else {return}
        let data = try! Data(contentsOf: urls[0])
        let subjectPDF = PDFDocument.init(data: data)
        guard subjectPDF!.isLocked == false else {return}

//Find temporary array of strings
        subjectPDF!.beginFindStrings(["the", "and"], withOptions: .caseInsensitive)

//Trigger results readout upon search competion
        NotificationCenter.default.addObserver(self, selector: #selector(onDidFindMatch(_:)), name: Notification.Name.PDFDocumentDidEndFind, object: nil)
    }

//Readout found strings to temporary label
    @objc func onDidFindMatch(_ notification: Notification) {
        resultsLabel.text = "\(String(describing: matchesFound?.string))"
    }

    func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
            dismiss(animated: true, completion: nil)
    }

}

---

这个问题是7个月前提出的，我希望你已经找到了解决办法。 无论如何，您的问题的解决方案是：

1-将下面的行移动到

viewDidLoad（）

，因为您是在触发

beginFindString（）

方法后添加观察者的

NotificationCenter.default.addObserver(self, selector: #selector(onDidFindMatch(_:)), name: Notification.Name.PDFDocumentDidEndFind, object: nil)

2-您从未为

matchesFound

变量赋值，因此它始终为零

3-要从

beginFindString

方法获取匹配项，您需要为

PDFDocumentDidFindMatch

添加一个观察者，并从

userInfo

而不是

PDFDocumentDidEndFind

获取数据。

PDFDocumentDidEndFind

observer将在搜索完成时被调用，例如，您可以使用此observer删除加载视图

以下是正确实现的示例代码：

var matchesFound = [PDFSelection]()

// MARK: Life cycle

override func viewDidLoad() {
    super.viewDidLoad()
    
    NotificationCenter.default.addObserver(self, selector: #selector(didFindMatch(_:)), name: NSNotification.Name.PDFDocumentDidFindMatch, object: nil)
}

deinit {
    NotificationCenter.default.removeObserver(self)
}

// This method will get called every-time a match has been found.
@objc private func didFindMatch(_ sender: Notification) {
    guard let selection = sender.userInfo?["PDFDocumentFoundSelection"] as? PDFSelection else { return }

    self.matchesFound.append(selection)
}

---

谢谢你回到一个老问题上来。我最终只是将它转换成文本，这对于我查询彼此接近的字符串来说更容易。