ios - 我以编程方式创建了 UIDatePicker 并让所选日期的 UILabel 显示，但未能让它正确显示

Question

我尝试在没有 Storyboard的情况下创建 UIDatePicker 并让所选日期的 UILabel 显示，但是当在模拟器上选择另一个日期时，标签显示为堆积。

- (void)viewDidLoad {
    [super viewDidLoad];

    UILabel *myLabel = [[UILabel alloc]initWithFrame:CGRectMake(10, 10,100,100)];
    [self.view addSubview:myLabel];

    UIDatePicker *myPicker = [[UIDatePicker alloc] initWithFrame:CGRectMake(10, 10, 200, 200)];

    myPicker.datePickerMode = UIDatePickerModeDate;

    [myPicker addTarget:self action:@selector(pickerChanged:) forControlEvents:UIControlEventValueChanged];

    [self.view addSubview:myPicker]; 
}


- (void)pickerChanged:(id)sender
{
     NSDateFormatter *df = [[NSDateFormatter alloc] init];   
     UILabel *myLabel = [[UILabel alloc]initWithFrame:CGRectMake(50, 300, 200, 200)];

     df.dateFormat = @"yyyy/MM/dd HH:mm";
     myLabel.text = [df stringFromDate:[sender date]];
     [self.view addSubview:myLabel];   
}

截图如下: http://i.stack.imgur.com/VnJbD.png

我是初学者，找不到解决方案。有人可以知道如何解决这个问题吗？提前谢谢你。

Answer 1

这是因为每次日期更改时您都在创建一个新标签

您需要重用您的组件，在加载 View 中创建它

- (void)viewDidLoad() {
    ....
   self.myLabel = [[UILabel alloc]initWithFrame:CGRectMake(50, 300, 200, 200)];
   [self.view addSubview:self.myLabel];
}

那么你就可以设置文本了:

- (void)pickerChanged:(id)sender {
    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    df.dateFormat = @"yyyy/MM/dd HH:mm";
    self.myLabel.text = [df stringFromDate:[sender date]]; 
}