ios - 从空白行开始 UIPickerView

Question

我的应用程序从服务器中提取数据以获取可供选择的当前组列表。然后它在这个名为“创建新组”的顶部添加一行。这很好用，但它开始时已经选择了这一行，所以我必须离开它，然后再次返回以选择它并激活键盘。我怎样才能再添加一个选项让它以空白行开头？我曾尝试简单地在行中执行 + 2 而不是 + 1，然后对所有内容进行排序，但它根本行不通。非常感谢任何帮助。

-(NSInteger)pickerView:(UIPickerView *)pickerView
numberOfRowsInComponent:(NSInteger)component{
    return [pickerArray count] + 1;
}

#pragma mark- Picker View Delegate

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:
(NSInteger)row inComponent:(NSInteger)component{
    if (row == 0)
    {
        [self.theView.signUpView.additionalField resignFirstResponder];
        self.theView.signUpView.additionalField.inputView = nil;
        [self.theView.signUpView.additionalField becomeFirstResponder];

    }
    else {

    [self.theView.signUpView.additionalField setText:self.theGroup];
    }
}
- (NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    NSString *groupName  = @"Create New Group";
    if (row != 0)
    {
        PFObject *object = pickerArray[row - 1]; // -1 to handle the array index
        self.theGroup    = object[@"GroupName"];
        groupName        = object[@"GroupName"];
    }
    return groupName;
}

Answer 1

此方法将您的数组调整为两个，允许您请求的空白空间。我还引入了 switch 语句，以便更容易理解正在发生的事情。在代码中添加了注释以突出显示与您的请求相关的更改。

#pragma mark- Picker View Delegate

-(NSInteger)pickerView:(UIPickerView *)pickerView
numberOfRowsInComponent:(NSInteger)component{
    return [pickerArray count] + 2; // This offsets your blank line & "Create new group" option
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
    return 1;
}

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:
(NSInteger)row inComponent:(NSInteger)component{
    switch (row) {
            // Ignore 0 here since you don't want to handle the blank space
            case 1:
            [self.theView.signUpView.additionalField resignFirstResponder];
            self.theView.signUpView.additionalField.inputView = nil;
            [self.theView.signUpView.additionalField becomeFirstResponder];
            break;
        default:
            [self.theView.signUpView.additionalField setText:self.theGroup];
    }
}
- (NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    switch (row) {
            case 0:
            return @"";
            case 1:
            return @"Create New Group";
        default:
            PFObject *object = pickerArray[row - 2];
            self.theGroup    = object[@"GroupName"];
            return self.theGroup;
    }
}

我包含了下面的图片，以显示使用一些通用数据时的样子。