iOS：UITextView與自定義NSTextStorage崩潰

Question

我正在Swift中編寫一個iOS 9應用程序。 我有一個托管UITextView的視圖控制器，我正在為它分配一個自定義的NSTextStorage對象。 NSTextStorage現在是基本的。 一切正常，文本顯示在UITextView中，但是當我點擊文本進行編輯時，應用程序崩潰時出現以下異常：

2016-01-10 11:24:32.931 PagesWriter[23750:6939530] requesting caretRectForPosition: with a position beyond the NSTextStorage (529)
2016-01-10 11:24:33.040 PagesWriter[23750:6939530] requesting caretRectForPosition: with a position beyond the NSTextStorage (529)
2016-01-10 11:24:33.168 PagesWriter[23750:6939530] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSCFString _getBlockStart:end:contentsEnd:forRange:stopAtLineSeparators:]: Range {529, 0} out of bounds; string length 245'
*** First throw call stack:
(0x181ea5900 0x181513f80 0x181ea5848 0x18278a02c 0x1827e963c 0x186cc6124 0x186b1c818 0x186cc5fbc 0x186d59e68 0x186bdeb60 0x186bde454 0x186fac1f8 0x187501f64 0x186bc2e84 0x186bc4f40 0x186fa65ac 0x186faea5c 0x186bc5c18 0x186bbf1f8 0x186bbed2c 0x186c2047c 0x186c20828 0x186d5811c 0x186d57f94 0x186d57448 0x187118dbc 0x186d3c5b8 0x186bca9b0 0x18711a3bc 0x186b89b58 0x186b868dc 0x186bc8820 0x186bc7e1c 0x186b984cc 0x186b96794 0x181e5cefc 0x181e5c990 0x181e5a690 0x181d89680 0x183298088 0x186c00d90 0x1000615ec 0x18192a8b8)
libc++abi.dylib: terminating with uncaught exception of type NSException

如果我從UITextView中刪除我的自定義NSTextStorage對象，它的工作原理。

我的視圖控制器使用故事板中的模態segue加載。 我加載文本內容並在viewDidLoad方法中配置UITextView和NSTextStorage對象：

class TextEditorViewController: UIViewController {
  @IBOutlet weak var textView: UITextView!

  // Set by parent view controller during transition
  var URL: NSURL?

  var textStorage: NSTextStorage?

  override func viewDidLoad() {
    super.viewDidLoad()

    textStorage = CustomTextStorage()
    textView.textStorage.removeLayoutManager(textView.layoutManager)
    textStorage!.addLayoutManager(textView.layoutManager)
    dispatch_async(UtilityQueue) {
      do {
        let text = try NSString(contentsOfURL: self.URL!, encoding: NSUTF8StringEncoding)
        dispatch_async(MainQueue) {
          self.textStorage!.replaceCharactersInRange(NSRange(location: 0, length: 0), withString: text as String)
        }
      } catch { /* handle error */ }
    }
  }
}

UtilityQueue和MainQueue是輔助內容，用於保存對相應調度隊列的引用。

我的自定義NSTextStorage類如下所示：

class CustomTextStorage: NSTextStorage {
  let backingStore = NSMutableAttributedString()

  override var string: String {
    return backingStore.string
  }

  override func attributedAtIndex(location: Int, effectiveRange range: NSRangePointer) -> [String: AnyObject] {
    return backingStore.attributesAtIndex(location, effectiveRange: range)
  }

  override func replaceCharactersInRange(range: NSRange, withString str: String) {
    backingStore.replaceCharactersInRange(range, withString: str)
    edited(.EditedCharacters, range: range, changeInLength: str.characters.count - range.length)
  }

  override func setAttributes(attires: [String: AnyObject]?, range: NSRange) {
    backingStore.setAttributes(attires, range: range)
    edited(.EditedAttributes, range: range, changeInLength: 0)
  }

  override func processEditing() {
    /* Placeholder; will be adding code here in the future. */
    super.processEditing()
  }
}

有任何想法嗎？ 提前感謝您的協助。

Answer 1

我不知道它是否仍然相關，但你幾乎是對的。

您需要分別調用beginEditing()和endEditing() 。

在長度計算中將字符串轉換為NSString以編輯回調（否則表情符號和其他一些情況將無法正常工作）。

另外，由於性能問題，請使用NSTextStorage作為backingStore。

你會得到這樣的東西：

final class ExampleStorage : NSTextStorage {

    private let container = NSTextStorage()

    override var string: String {
        return container.string
    }

    override func attributes(at location: Int, effectiveRange range: NSRangePointer?) -> [NSAttributedStringKey : Any] {
        return container.attributes(at: location, effectiveRange: range)
    }

    override func replaceCharacters(in range: NSRange, with str: String) {
        beginEditing()
        container.replaceCharacters(in: range, with: str)
        edited([.editedAttributes, .editedCharacters], range: range, changeInLength: (str as NSString).length - range.length)
        endEditing()
    }

    override func setAttributes(_ attrs: [NSAttributedStringKey : Any]?, range: NSRange) {
        beginEditing()
        container.setAttributes(attrs, range: range)
        edited([.editedAttributes], range: range, changeInLength: 0)
        endEditing()
    }
}