要求 UITextField 取 5 位数

Question

我设置了一个 UITextField 来显示数字键盘。我如何要求用户准确输入 5 位数字？

我四处寻找，发现我应该使用 shouldChangeCharactersInRange，但我不太了解如何实现它。

Answer 1

- (BOOL) textField: (UITextField *)textField shouldChangeCharactersInRange: (NSRange)range replacementString: (NSString *)string {

    NSString *newText = [textField.text stringByReplacingCharactersInRange: range withString: string];

    return [self validateText: newText]; // Return YES if newText is acceptable 

}

Answer 2

我只会在用户使用按钮

离开textfield/validates时使用它

if ([myTextField.text length] != 5){

//Show alert or some other warning, like a red text

}else{
 //Authorized text, proceed with whatever you are doing
}

现在如果你想在用户输入时计算字符数，你可以使用 in viewDidLoad

[myTextfield addTarget: self action@selector(textfieldDidChange:) forControlEvents:UIControlEventsEditingChanged]

-(void)textFieldDidChange:(UITextField*)theTextField{
 //This happens every time the textfield changes
}

如果您需要更多帮助，请务必在评论中提出问题:)

Answer 3

让自己成为 UITextFieldDelegate 的代表并执行以下操作：

- (BOOL)textField:(UITextField *) textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

        NSUInteger oldLength = [textField.text length];
        NSUInteger replacementLength = [string length];
        NSUInteger rangeLength = range.length;

        NSUInteger newLength = oldLength - rangeLength + replacementLength;

        BOOL returnKey = [string rangeOfString: @"\n"].location != NSNotFound;

        //desired length less than or equal to 5
        return newLength <= 5 || returnKey;
    }

要求 UITextField 取 5 位数

Require a UITextField to take 5 digits

objective-c

uitextfield

uitextfielddelegate