Question

我正在开发一个自定义iOS键盘 - 其中大部分已经到位，但我在删除键时出现问题，更具体地说是删除整个单词。

问题是即使文本字段中还有字符，self.textDocumentProxy.documentContextBeforeInput？.isEmpty也会返回Nil。

以下是背景资料：如果您不熟悉，它在iOS键盘上的工作方式是，在按住退格键时，系统一次删除一个字符（对于前10个字符）。在10个字符后，它开始删除整个单词。

在我的代码的情况下，我删除10个单个字符然后我成功删除了几个完整的单词，然后突然self.textDocumentProxy.documentContextBeforeInput？.isEmpty返回Nil，即使文本中还有剩余字符字段。

我看了很多文档和网页，我没有看到其他人有同样的问题，所以我确定我错过了一些明显的东西，但我很困惑。

以下是我班级定义的相关部分：

class KeyboardViewController: UIInputViewController { 

//I've removed a bunch of variables that aren't relevant to this question.

    var myInputView : UIInputView {
    return inputView!
}
private var proxy: UITextDocumentProxy {
    return textDocumentProxy
}
override func canBecomeFirstResponder() -> Bool {
    return true
}

override func viewDidLoad() {
    super.viewDidLoad()
    //proxy let proxy = self.textDocumentProxy


    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillAppear"), name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide"), name: UIKeyboardWillHideNotification, object: nil)


    self.myInputView.translatesAutoresizingMaskIntoConstraints = true

    // Perform custom UI setup here
    view.backgroundColor = UIColor(red: 209 / 255, green: 213 / 255, blue: 219 / 255, alpha: 1)

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "touchUpInsideLetter:", name: "KeyboardKeyPressedNotification", object: nil)

    showQWERTYKeyboard()
}

我为退格按钮设置了监听器和操作，因为我还在按钮上配置了一堆其他属性。我在Switch中这样做 - 相关部分在这里：

case "<<":
            isUIButton = true
            normalButton.setTitle(buttonString, forState: UIControlState.Normal)
            normalButton.addTarget(self, action: "turnBackspaceOff", forControlEvents: UIControlEvents.TouchUpInside)
            normalButton.addTarget(self, action: "turnBackspaceOff", forControlEvents: UIControlEvents.TouchUpOutside)
            normalButton.addTarget(self, action: "touchDownBackspace", forControlEvents: UIControlEvents.TouchDown)
            let handleBackspaceRecognizer : UILongPressGestureRecognizer = UILongPressGestureRecognizer(target: self, action: "handleBackspaceLongPress:")
            normalButton.addGestureRecognizer(handleBackspaceRecognizer)

            buttonWidth = standardButtonWidth * 1.33
            nextX = nextX + 7

感谢您的任何想法。

****修改原帖以帮助更多地了解问题**** 以下是用于创建退格行为的4个函数。它们似乎至少在前两个单词中正常工作，但是正确建议的可选检查开始评估为nil并且它会停止删除。

    //Gets called on "Delete Button TouchUpInside" and "Delete Button TouchUpOutside"
func turnBackspaceOff() {

    self.backspaceIsPressed = false
    keyRepeatTimer.invalidate()

}

//Handles a single tap backspace
func touchDownBackspace() {

    (textDocumentProxy as UIKeyInput).deleteBackward()

}

//Handles a long press backspace
func handleBackspaceLongPress(selector : UILongPressGestureRecognizer) {

    if selector.state == UIGestureRecognizerState.Began {
        self.backspaceIsPressed = true
        self.keyRepeatTimer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: "backspaceRepeatHandlerFinal", userInfo: nil, repeats: true)
        print("handleBackspaceLongPress.Began")
    }
    else if selector.state == UIGestureRecognizerState.Ended {
        self.backspaceIsPressed = false
        keyRepeatTimer.invalidate()
        numberOfKeyPresses = 0
        print("handleBackspaceLongPress.Ended")
    }
    else {
        self.backspaceIsPressed = false
        keyRepeatTimer.invalidate()
        numberOfKeyPresses = 0
        print("handleBackspaceLongPress. Else")
    }

}

func backspaceRepeatHandlerFinal() {

        if let documentContext = proxy.documentContextBeforeInput as String? {
            print(documentContext)
        }

        print("backspaceRepeatHandlerFinal is called")
        if self.backspaceIsPressed {
            print("backspace is pressed")
            self.numberOfKeyPresses = self.numberOfKeyPresses + 1

            if self.numberOfKeyPresses < 10 {

                    proxy.deleteBackward()

            }
            else {

                if let documentContext = proxy.documentContextBeforeInput as NSString? {
                        let tokens : [String] = documentContext.componentsSeparatedByString(" ")
                        var i : Int = Int()
                    for i = 0; i < String(tokens.last!).characters.count + 1; i++ {
                            (self.textDocumentProxy as UIKeyInput).deleteBackward()
                        }

                }
                else {
                    print("proxy.documentContextBeforeInput was nil")
                    self.keyRepeatTimer.invalidate()
                    self.numberOfKeyPresses = 0
                }
            }
        }
        else {
            print("In the outer else")
            self.keyRepeatTimer.invalidate()
            self.numberOfKeyPresses = 0
        }
}

最后，我不完全理解为什么，但是当我创建键盘扩展时，XCode会自动在下面插入这两个函数。为了试图让它发挥作用，我稍微修改了它们。

    override func textWillChange(textInput: UITextInput?) {
    // The app is about to change the document's contents. Perform any preparation here.
    super.textWillChange(textInput)
}

override func textDidChange(textInput: UITextInput?) {
    // The app has just changed the document's contents, the document context has been updated.

    var textColor: UIColor
    //let proxy = self.textDocumentProxy
    if proxy.keyboardAppearance == UIKeyboardAppearance.Dark {
        textColor = UIColor.whiteColor()
    } else {
        textColor = UIColor.blackColor()
    }
    super.textDidChange(textInput)
}

Answer 1

让我们来描述下面这一行：

if !((self.textDocumentProxy.documentContextBeforeInput?.isEmpty) == nil) {

首先，它需要一个标记为optional的对象（?字母）：

let documentContext = self.textDocumentProxy.documentContextBeforeInput

然后，它尝试读取它的名为isEmpty的属性：

let isEmpty = documentContext?.isEmpty

然后评估结果：

if !(isEmpty == nil) {

有两个错误。第一个是您将Bool值与nil进行比较。另一个原因是您不确定documentContext不是nil。

所以，让我们以更合适的方式编写代码：

if let documentContext = self.textDocumentProxy.documentContextBeforeInput { // Make sure that it isn't nil
    if documentContext.isEmpty == false { // I guess you need false?
        // Do what you want with non-empty document context
    }
}

iOS键盘：textDocumentProxy.documentContextBeforeInput.isEmpty意外返回Nil（不应该）

1 个答案: