ios 检测 UITextField 中的退格事件

Question

提问by Want Query

I am searching for solutions on how to capture a backspace event, most Stack Overflow answers are in Objective-C but I need on Swift language.

我正在寻找有关如何捕获退格事件的解决方案，大多数 Stack Overflow 答案都在 Objective-C 中，但我需要 Swift 语言。

First I have set delegate for the UITextField and set it to self

首先，我为 UITextField 设置了委托并将其设置为 self

self.textField.delegate = self;

Then I know to use shouldChangeCharactersInRangedelegate method to detect if a backspace was pressed is all code are in Objective-C. I need in Swift these following method as below is used.

然后我知道使用shouldChangeCharactersInRange委托方法来检测是否按下了退格键，所有代码都在 Objective-C 中。我需要在 Swift 中使用以下方法，如下所示。

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    const char * _char = [string cStringUsingEncoding:NSUTF8StringEncoding];
    int isBackSpace = strcmp(_char, "\b");

    if (isBackSpace == -8) {
        // NSLog(@"Backspace was pressed");
    }

    return YES;
}

Answer 1

回答by Long Pham

Swift 4.2

斯威夫特 4.2

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    if let char = string.cString(using: String.Encoding.utf8) {
        let isBackSpace = strcmp(char, "\b")
        if (isBackSpace == -92) {
            print("Backspace was pressed")
        }
    }
    return true
}

Older Swift version

较旧的 Swift 版本

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let  char = string.cStringUsingEncoding(NSUTF8StringEncoding)!
    let isBackSpace = strcmp(char, "\b")

    if (isBackSpace == -92) {
        println("Backspace was pressed")
    }
    return true
}

Answer 2

回答by Ortwin Gentz

I prefer subclassing UITextFieldand overriding deleteBackward()because that is much more reliable than the hack of using shouldChangeCharactersInRange:

我更喜欢子类化UITextField和覆盖，deleteBackward()因为这比使用 hack 可靠得多shouldChangeCharactersInRange：

class MyTextField: UITextField {
    override public func deleteBackward() {
        if text == "" {
             // do something when backspace is tapped/entered in an empty text field
        }
        // do something for every backspace
        super.deleteBackward()
    }
}

The shouldChangeCharactersInRangehack combined with an invisible character that is placed in the text field has several disadvantages:

该shouldChangeCharactersInRange黑客与被放置在文本字段中有不可见字符组合有几个缺点：

with a keyboard attached, one can place the cursor before the invisible character and the backspace isn't detected anymore,
the user can even select that invisible character (using Shift Arrowon a keyboard or even by tapping on the caret) and will be confused about that weird character,
the autocomplete bar offers weird choices as long as there's only this invisible character,
Asian language keyboards that have candidate options based on the text field's text will be confused,
the placeholderisn't shown anymore,
the clear button is displayed even when it shouldn't for clearButtonMode = .whileEditing.

连接键盘后，可以将光标放在不可见字符之前，不再检测到退格，
用户甚至可以选择那个不可见的字符（Shift Arrow在键盘上使用，甚至通过点击插入符号）并且会对那个奇怪的字符感到困惑，
只要只有这个不可见的字符，自动完成栏就会提供奇怪的选择，
具有基于文本字段文本的候选选项的亚洲语言键盘将被混淆，
在placeholder不再被示出，
即使不应该显示清除按钮clearButtonMode = .whileEditing。

Of course, overriding deleteBackward()is a bit inconvenient due to the need of subclassing. But the better UX makes it worth the effort!

当然，deleteBackward()由于需要子类化，覆盖有点不方便。但更好的 UX 让它值得付出努力！

And if subclassing is a no-go, e.g. when using UISearchBarwith its embedded UITextField, method swizzling should be fine, too.

如果子类化是行不通的，例如当使用UISearchBar其嵌入时UITextField，方法 swizzling 也应该没问题。

Answer 3

回答by Insou

In Swift 3

在斯威夫特 3

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    let  char = string.cString(using: String.Encoding.utf8)!
    let isBackSpace = strcmp(char, "\b")

    if (isBackSpace == -92) {
         print("Backspace was pressed")
    }
    return true
}

:)

Answer 4

回答by gbk

If u need detect backspace even in empty textField (for example in case if u need auto switch back to prev textField on backSpace pressing), u can use combination of proposed methods - add invisible sign and use standard delegate method textField:shouldChangeCharactersInRange:replacementString:like follow

如果即使在空的 textField 中您也需要检测退格（例如，如果您需要在按下退格键时自动切换回上一个 textField），您可以使用建议方法的组合 - 添加不可见符号并使用标准委托方法，textField:shouldChangeCharactersInRange:replacementString:例如 follow

Create invisible sign

private struct Constants {
    static let InvisibleSign = "\u{200B}"
}

Set delegate for textField
```
textField.delegate = self
```

On event EditingChangedcheck text and if needed add invisible symbol like follow:

@IBAction func didChangeEditingInTextField(sender: UITextField) {
    if var text = sender.text {
        if text.characters.count == 1 && text != Constants.InvisibleSign {
            text = Constants.InvisibleSign.stringByAppendingString(text)
            sender.text = text
        }
    }
}

创建隐形标志

private struct Constants {
    static let InvisibleSign = "\u{200B}"
}

为 textField 设置委托
```
textField.delegate = self
```

在事件EditingChanged检查文本上，如果需要，添加不可见符号，如下所示：

@IBAction func didChangeEditingInTextField(sender: UITextField) {
    if var text = sender.text {
        if text.characters.count == 1 && text != Constants.InvisibleSign {
            text = Constants.InvisibleSign.stringByAppendingString(text)
            sender.text = text
        }
    }
}

Add implementation of delegate method textField:shouldChangeCharactersInRange:replacementString:

extension UIViewController : UITextFieldDelegate {
    // MARK: - UITextFieldDelegate
    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

        let  char = string.cStringUsingEncoding(NSUTF8StringEncoding)!
        let isBackSpace = strcmp(char, "\b")

        if (isBackSpace == -92) {
            if var string = textField.text {
                string = string.stringByReplacingOccurrencesOfString(Constants.InvisibleSign, withString: "")
                if string.characters.count == 1 {
                    //last visible character, if needed u can skip replacement and detect once even in empty text field
                    //for example u can switch to prev textField 
                    //do stuff here                            
                }
            }
        }
        return true
    }
}

添加委托方法的实现 textField:shouldChangeCharactersInRange:replacementString:

extension UIViewController : UITextFieldDelegate {
    // MARK: - UITextFieldDelegate
    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

        let  char = string.cStringUsingEncoding(NSUTF8StringEncoding)!
        let isBackSpace = strcmp(char, "\b")

        if (isBackSpace == -92) {
            if var string = textField.text {
                string = string.stringByReplacingOccurrencesOfString(Constants.InvisibleSign, withString: "")
                if string.characters.count == 1 {
                    //last visible character, if needed u can skip replacement and detect once even in empty text field
                    //for example u can switch to prev textField 
                    //do stuff here                            
                }
            }
        }
        return true
    }
}

Answer 5

回答by Dmitry Kozlov

Please don't trash your code. Just put this extension somewhere in your code.

请不要丢弃您的代码。只需将此扩展名放在代码中的某个位置即可。

Swift 5.1

斯威夫特 5.1

extension String {
  var isBackspace: Bool {
    let char = self.cString(using: String.Encoding.utf8)!
    return strcmp(char, "\b") == -92
  }
}

And then just use it in your functions

然后在你的函数中使用它

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
  if string.isBackspace {
    // do something
  }
  return true
}

Answer 6

回答by Augustine P A

Try this

尝试这个

public func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

if(string == "") {

        print("Backspace pressed");
        return true;
    }
}

Note: You can return "true" if you want to allow backspace. Else you can return "false".

注意：如果你想允许退格，你可以返回“ true”。否则你可以返回“ false”。

Answer 7

回答by Roman Romanenko

I implemented this feature:

我实现了这个功能：

And in the case where the last textFiled is empty, I just want to switch to the previous textFiled. I tried all of the answers above, but no one works fine in my situation. For some reason, if I add more logic than printin isBackSpace == -92parentheses block this method just stopped work...

而在最后一个 textFiled 为空的情况下，我只想切换到上一个 textFiled。我尝试了上面的所有答案，但没有一个在我的情况下工作正常。出于某种原因，如果我不是增加更多的逻辑print在isBackSpace == -92括号阻止这种方法刚刚停止工作...

As for me the method below more elegant and works like a charm:

至于我，下面的方法更优雅，而且效果很好：

Swift

迅速

class YourTextField: UITextField {

    // MARK: Life cycle

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

    // MARK: Methods

    override func deleteBackward() {
        super.deleteBackward()

        print("deleteBackward")
    }

}

Thanks @LombaX for the answer

感谢@LombaX 的回答

Answer 8

回答by Amr Angry

Swift 4

斯威夫特 4

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

            let  char = string.cString(using: String.Encoding.utf8)!
            let isBackSpace = strcmp(char, "\b")

            if isBackSpace == -92 {
                print("Backspace was pressed")
                return false
            }
}

Answer 9

回答by GreenCamper

Swift 4

斯威夫特 4

I find the comparison using strcmpirrelevant. We don't even know how strcmpis operating behind the hoods.In all the other answers when comparing current char and \bresults are -8in objective-C and -92in Swift. I wrote this answer because the above solutions did not work for me. ( Xcode Version 9.3 (9E145)using Swift 4.1)

我发现使用strcmp不相关的比较。我们甚至不知道strcmp幕后是如何操作的。在比较当前字符和\b结果时，所有其他答案都-8在 Objective-C 和-92Swift 中。我写这个答案是因为上述解决方案对我不起作用。（9.3 (9E145)使用 Swift 的Xcode 版本4.1）

FYI :Every character that you actually type is an array of 1or more elements in utf8 Encoding. backSpace Character is [0]. You can try this out.

FYI：你实际键入的每个字符是一个数组1或多个元素utf8 Encoding。退格字符是[0]. 你可以试试这个。

PS :Don't forget to assign the proper delegatesto your textFields.

PS：不要忘记delegates为您的textFields.

public func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let  char = string.cString(using: String.Encoding.utf8)!
    if (char.elementsEqual([0])) {
        print("Backspace was pressed")
    }
    else {
        print("WHAT DOES THE FOX SAY ?\n")
        print(char)
    }
    return true
}

Answer 10

回答by Shakeel Ahmed

Swift 4

斯威夫特 4

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    //MARK:- If Delete button click
    let  char = string.cString(using: String.Encoding.utf8)!
    let isBackSpace = strcmp(char, "\b")

    if (isBackSpace == -92) {
        print("Backspace was pressed")

        return true
    }
}

ios 检测 UITextField 中的退格事件

提问by Want Query

回答by Long Pham

回答by Ortwin Gentz

回答by Insou

回答by gbk

回答by Dmitry Kozlov

Swift 5.1

斯威夫特 5.1

回答by Augustine P A

回答by Roman Romanenko

回答by Amr Angry

Swift 4

斯威夫特 4

回答by GreenCamper

Swift 4

斯威夫特 4

回答by Shakeel Ahmed

相关推荐

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标签

ios 检测 UITextField 中的退格事件

提问by Want Query

回答by Long Pham

回答by Ortwin Gentz

回答by Insou

回答by gbk

回答by Dmitry Kozlov

Swift 5.1

斯威夫特 5.1

回答by Augustine P A

回答by Roman Romanenko

回答by Amr Angry

Swift 4

斯威夫特 4

回答by GreenCamper

Swift 4

斯威夫特 4

回答by Shakeel Ahmed

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