仅允许 UITextField 输入的数字 [英] Allow only Numbers for UITextField input

问题描述

iPad 没有 iPhone/iPod 那样的Numpad"键盘.

The iPad does not have a "Numpad" keyboard like the iPhone/iPod does.

我正在寻找如何将用户的键盘限制为仅接受 0 到 9 的值.

I'm looking to find how I can restrict the user's keyboard to only accept values 0 through 9.

我想使用 UITextField 的shouldChangeCharactersInRange"，但我不知道实现它的最佳方法.

I would imagine using UITextField's "shouldChangeCharactersInRange" but I don't know the best way to implement it.

推荐答案

这是你处理 SSN 验证字段问题的方法，你可以修改最大长度并删除 if 语句检查如果需要，用于键盘类型.

This is how you might handle the problem on a SSN verification field, you can modify the max length and remove the if statement checking for keyboard type if you need to.

当用户输入而不是粘贴数据时，还有一个逻辑可以抑制最大长度警报.

There is also logic to suppress the max length alerts when the user is typing as opposed to pasting data.

在这段代码的上下文中，presentAlert()/presentAlert: 只是一些基本函数，它呈现了一个 UIAlertController(或一个遗留的 UIAlertView>) 使用传递的消息字符串.

Within the context of this code, presentAlert()/presentAlert: is just some basic function that presents a UIAlertController (or a legacy UIAlertView) using the message string passed.

// NOTE: This code assumes you have set the UITextField(s)'s delegate property to the 
// object that will contain this code, because otherwise it would never be called.
//
// There are also some better stylistic approaches in Swift to avoid all the 
// nested statements, but I wanted to keep the styles similar to allow others 
// to contrast and compare between the two languages a little easier.

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

    // Handle backspace/delete
    guard !string.isEmpty else {

        // Backspace detected, allow text change, no need to process the text any further
        return true
    }

    // Input Validation
    // Prevent invalid character input, if keyboard is numberpad
    if textField.keyboardType == .numberPad {

        // Check for invalid input characters
        if CharacterSet(charactersIn: "0123456789").isSuperset(of: CharacterSet(charactersIn: string)) {

            // Present alert so the user knows what went wrong
            presentAlert("This field accepts only numeric entries.")

            // Invalid characters detected, disallow text change
            return false
        }
    }

    // Length Processing
    // Need to convert the NSRange to a Swift-appropriate type
    if let text = textField.text, let range = Range(range, in: text) {

        let proposedText = text.replacingCharacters(in: range, with: string)

        // Check proposed text length does not exceed max character count
        guard proposedText.count <= maxCharacters else {

            // Present alert if pasting text
            // easy: pasted data has a length greater than 1; who copy/pastes one character?
            if string.count > 1 {

                // Pasting text, present alert so the user knows what went wrong
                presentAlert("Paste failed: Maximum character count exceeded.")
            }

            // Character count exceeded, disallow text change
            return false
        }

        // Only enable the OK/submit button if they have entered all numbers for the last four
        // of their SSN (prevents early submissions/trips to authentication server, etc)
        answerButton.isEnabled = (proposedText.count == 4)
    }

    // Allow text change
    return true
}

目标-C

// NOTE: This code assumes you have set the UITextField(s)'s delegate property to the 
// object that will contain this code, because otherwise it would never be called.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // Handle backspace/delete
    if (!string.length)
    {
        // Backspace detected, allow text change, no need to process the text any further
        return YES;
    }

    // Input Validation
    // Prevent invalid character input, if keyboard is numberpad
    if (textField.keyboardType == UIKeyboardTypeNumberPad)
    {
        if ([string rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet].invertedSet].location != NSNotFound)
        {
            [self presentAlert: @"This field accepts only numeric entries."];
            return NO;
        }
    }

    // Length Validation
    NSString *proposedText = [textField.text stringByReplacingCharactersInRange:range withString:string];

    // Check proposed text length does not exceed max character count
    if (proposedText.length > maxCharacters)
    {
        // Present alert if pasting text
        // easy: pasted data has a length greater than 1; who copy/pastes one character?
        if (string.length > 1)
        {
            // Pasting text, present alert so the user knows what went wrong
            [self presentAlert: @"Paste failed: Maximum character count exceeded."];
        }

        // Character count exceeded, disallow text change
        return NO;
    }

    // Only enable the OK/submit button if they have entered all numbers for the last four
    // of their SSN (prevents early submissions/trips to authentication server, etc)
    self.answerButton.enabled = (proposedText.length == maxCharacters);

    // Allow text change
    return YES;
}

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