观察UIDatePicker中的更改

Question

我注意到没有委托来观察UIDatePicker中的更改。有没有办法检测何时在选择器中进行更改而不确认任何内容，例如它旋转并落在我希望能够检测到的新数字上的那一刻。我想到了关键的价值观察，但我不认为那里有一个现场变化的财产

Answer 1

您需要将UIControlEventValueChanged事件添加到您的UIDatePicker以处理日期更改：

[myDatePicker addTarget:self action:@selector(dateIsChanged:) forControlEvents:UIControlEventValueChanged];

然后执行：

- (void)dateIsChanged:(id)sender{
     NSLog(@"Date changed");
}

Answer 2

转到IB并从UIDatePicker拖动到.h文件。然后选择

在你的.m文件中处理你想要的内容; XCode将为您添加以下方法。

Answer 3

以下是符合KVO标准的日期选择器的提案：

@interface LNKVODatePicker : UIDatePicker

@end

@implementation LNKVODatePicker

- (void)willMoveToWindow:(UIWindow *)newWindow
{
    [super willMoveToWindow:newWindow];

    [self removeTarget:self action:@selector(_didChangeDate) forControlEvents:UIControlEventValueChanged];

    if(newWindow != nil)
    {
        [self addTarget:self action:@selector(_didChangeDate) forControlEvents:UIControlEventValueChanged];
    }
}

- (void)dealloc
{
    [self removeTarget:self action:@selector(_didChangeDate) forControlEvents:UIControlEventValueChanged];
}

- (void)_didChangeDate
{
    [self willChangeValueForKey:@"date"];
    [self didChangeValueForKey:@"date"];
}

@end

Answer 4

Swift 4.2 | Xcode 10.1

@objc func handleDatePicker(_ datePicker: UIDatePicker) {
    textField.text = datePicker.date.formatted
}

override func viewDidLoad() {
    super.viewDidLoad()
    datePicker.addTarget(self, action: #selector(handleDatePicker), for: .valueChanged)
}

---

extension Date {
    static let formatter: DateFormatter = {
        let formatter = DateFormatter()
        formatter.dateFormat = "EEEE, dd MMM yyyy HH:mm:ss Z"
        return formatter
    }()
    var formatted: String {
        return Date.formatter.string(from: self)
    }
}