UIDatePicker 选择的值被隐藏

Question

我正在以编程方式创建一个UIDatePicker，允许选择日期（日/月/年）。

当我滚动选择输入（日、月或年）时，所选值总是隐藏的。截图如下：

我不知道这是什么错误，也没有在 Stackoverflow 上找到任何解决方案。

使用的代码：

CGRect datePickerFrame = CGRectMake(0, 40, self.view.frame.size.width, 216);
UIDatePicker *datePicker = [[UIDatePicker alloc] initWithFrame:datePickerFrame];
[self.view addSubview:datePicker];

这个错误发生在iPhone 5S iOS 9.2.1 编程语言：Objective-C

Answer 1

尝试以下代码；

    CGRect datePickerFrame = CGRectMake(0, 40, self.view.frame.size.width, 216);
    UIDatePicker *datePicker = [[UIDatePicker alloc]initWithFrame:datePickerFrame];
    datePicker.datePickerMode=UIDatePickerModeDate;
    datePicker.hidden=NO;
    datePicker.date=[NSDate date];
    [datePicker addTarget:self action:@selector(LabelTitle:) forControlEvents:UIControlEventValueChanged];
    [self.view addSubview:datePicker];

-(void)LabelTitle:(id)sender
{
    NSDateFormatter *dateFormat=[[NSDateFormatter alloc]init];
    dateFormat.dateStyle=NSDateFormatterMediumStyle;
    [dateFormat setDateFormat:@"dd/MM/yyyy"];
    NSString *str=[NSString stringWithFormat:@"%@",[dateFormat  stringFromDate:datePicker.date]];
    //assign text to label
    label.text=str; 

Answer 2

只是通过更改颜色进行测试可能是我不确定的问题

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
 UILabel *labelSelected = (UILabel*)[pickerView viewForRow:row forComponent:component];
[labelSelected setTextColor:[UIColor redColor]];
}