编辑时更改 uitextfield 返回键类型

我有 4 个 uitextfields 可以识别它们何时为空或完整。如果完成，他们会将返回键类型更改为 GO，否则为默认类型。问题是即使我使用 reloadinputview 键盘也不会更改按键类型

- (void)viewDidLoad
{
    [super viewDidLoad];

    _fieldsArray = @[_nameField, _passwordField, _emailField, _usernameField];
}

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

    NSRange textFieldRange = NSMakeRange(0, [textField.text length]);

    //NSLog(@"%d", !(NSEqualRanges(range, textFieldRange) && [string length] == 0));

    [self signUpFieldsAreValid:(!(NSEqualRanges(range, textFieldRange) && [string length] == 0) && [self validateSignUpFields:textField])];
    [textField reloadInputViews];
    return YES;
}
- (BOOL)textFieldShouldClear:(UITextField *)textField{

    [self signUpFieldsAreValid:NO];
    [textField reloadInputViews];
    return YES;
}

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
    for (UITextField *aTextField in _fieldsArray) {
        if (aTextField.isFirstResponder) {

            aTextField.layer.borderWidth = 0.f;
            aTextField.layer.borderColor = nil;

        }
    }

    textField.layer.borderWidth = 1.f;
    textField.layer.borderColor = [UIColor colorWithRed:200.f/255.f green:0.f/255.f blue:4.f/255.f alpha:1.f].CGColor;

    return YES;
}

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    NSUInteger fieldIndex = [_fieldsArray indexOfObject:textField];

    [_fieldsArray[(fieldIndex + 1) % 4] becomeFirstResponder];

    return YES;
}

- (BOOL)validateSignUpFields:(UITextField *)firstResponder
{
    for (UITextField *aTextField in _fieldsArray) {
        if (!aTextField.text.length && ![aTextField isEqual:firstResponder]) {
            return NO;
        }
    }

    return YES;
}

- (void)signUpFieldsAreValid:(BOOL)valid
{
    NSLog(@"%d", valid);
    for (UITextField *aTextField in _fieldsArray) {

        if (valid) {
            aTextField.returnKeyType = UIReturnKeyGo;
        }
        else {
            aTextField.returnKeyType = UIReturnKeyDefault;
        }
    }
}

我在更改 returnKeyType 后使用了以下内容，它似乎在 iOS7 和 iOS6.1 中运行得很好：

if ([self.textfieldOne isFirstResponder]) {
    [self.textfieldOne reloadInputViews];

}