我无法拦截 Numpad 的后退按钮

Question

当按下返回键或返回键时，我希望 firstResponder 转到前一个 TextField。但是 textFieldShouldReturn 没有启动。非常感谢你们！

试过this，但似乎不起作用。

MyViewController.h

@interface MyViewController : UIViewController <UITextFieldDelegate>

@property (strong, nonatomic) IBOutlet UITextField *firstCodeField;

MyViewController.m

@synthesize firstCodeField;

- (void)viewDidLoad
{
[super viewDidLoad];
firstCodeField.delegate = self;
secondCodeField.delegate = self;
thirdCodeField.delegate = self;
fourthCodeField.delegate = self;
fifthCodeField.delegate = self;
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSUInteger newLength = [textField.text length] + [string length] - range.length;

    if (string.length == 0 && textField.text.length)
    {
        if(textField==fifthCodeField) {
            NSLog(@"It goes to fourth textfield but doesn't clear the number in the cell.");
            [textField resignFirstResponder];
            [fourthCodeField becomeFirstResponder];
            return NO;
        }
    }

    return (newLength > 1) ? NO : YES;
}

Answer 1

必须在textField :shouldChangeCharactersInRange:中识别退格

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
      {
        if (string.length == 0 //BackSpace
            && textField.text.length)//No Characters in text field
        {
            [textField resignFirstResponder];
            return NO;
        }
        return YES;
    }

更新的答案。当第五个字段为空时，单击退格会移动到第四个字段并清除第四个字段的最后一个字符

    - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
    {
        NSUInteger newLength = [textField.text length] + [string length] - range.length;

        if (string.length == 0 && textField.text.length)
        {
            if(textField==fifthCodeField) {
                NSLog(@"It goes to fourth textfield but doesn't clear the number in the cell.");
                [textField resignFirstResponder];

                //Character range for last character
                NSRange fourthFieldRange;
                range.length = 1;
                range.location = field.text.length - 1;

                NSString *text = [fourthCodeField.text stringByReplacingCharactersInRange:fourthFieldRange withString:@""];
                 [fourthCodeField becomeFirstResponder];
                return NO;
            }
        }

        return (newLength > 1) ? NO : YES;
    }