UIDatePicker(日期时刻选择框)

1、基本用法：

    UIDatePicker * datePicker = [[UIDatePicker alloc] init];
    [self.view addSubview:datePicker];

只需要这两行代码就能显示一个日起时刻选择框：

2、自定义日期时刻选择框的大小位置：

    datePicker.frame = CGRectMake(50, 100, 350, 500);

3、日期时刻选择框的几种样式：

（1）默认：

    datePicker.datePickerMode = UIDatePickerModeDateAndTime;//默认

就是上面的那种形式。

（2）、

    datePicker.datePickerMode = UIDatePickerModeTime;

显示当前时间：

（3）、

    datePicker.datePickerMode = UIDatePickerModeDate;

显示当前日期：

（4）、

    datePicker.datePickerMode = UIDatePickerModeCountDownTimer;

倒计时模式：

4、实时监测：

添加事件：

    [datePicker addTarget:self action:@selector(datePickerChange:) forControlEvents:UIControlEventValueChanged];

响应事件（只有滚动停止的时候才响应事件，滚动期间不响应）：

- (void) datePickerChange:(id) sender {
    if ([sender isKindOfClass:[UIDatePicker class]]) {
        UIDatePicker * datePicker = sender;

        NSDateFormatter * formatter = [[NSDateFormatter alloc] init];
        [formatter setDateFormat:@"yy/MM/dd HH:mm"];
        NSString * dateString = [formatter stringFromDate:datePicker.date];
        NSLog(@"%@", dateString);
    }
}

滑动日期时刻选择器，实时输出：

2015-11-27 10:49:03.584 07-UIDatePicker[609:9234] 15/11/27 00:49
2015-11-27 10:49:05.851 07-UIDatePicker[609:9234] 15/11/27 02:49
2015-11-27 10:49:12.975 07-UIDatePicker[609:9234] 15/11/27 04:49
2015-11-27 10:49:15.284 07-UIDatePicker[609:9234] 15/11/27 05:49
2015-11-27 10:49:17.141 07-UIDatePicker[609:9234] 15/11/27 07:49
2015-11-27 10:49:20.855 07-UIDatePicker[609:9234] 15/11/27 14:49

5、手动设置日期，并且改变时是否伴随动画形式：

- (void)setDate:(NSDate *)date animated:(BOOL)animated; // if animated is YES, animate the wheels of time to display the new date

6、设置时间间隔：

 @property (nonatomic) NSInteger      minuteInterval;    // display minutes wheel with interval. interval must be evenly divided into 60. default is 1. min is 1, max is 30

默认是1，最小是1，最大是30分钟

    datePicker.minuteInterval = 20;

7、设置日期选择范围：

 @property (nullable, nonatomic, strong) NSDate *minimumDate; // specify min/max date range. default is nil. When min > max, the values are ignored. Ignored in countdown timer mode
 @property (nullable, nonatomic, strong) NSDate *maximumDate; // default is nil

设置范围为：

    datePicker.minimumDate = [NSDate date];
    datePicker.maximumDate = [NSDate dateWithTimeIntervalSinceNow:60 * 60 * 24 * 25];

此时无论怎么向下滑，日期最终也只是停在Today，不会小于Today

此时无论怎么向上滑，日期最后总是停在Tue Dec 22处，不可能大于这个日期。

8、倒计时模式：

#import "ViewController.h"

@interface ViewController ()
{
    UIDatePicker * datePicker;
    NSTimer * timer;
}
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.view.backgroundColor = [UIColor whiteColor];

    datePicker = [[UIDatePicker alloc] init];
    [self.view addSubview:datePicker];
    datePicker.frame = CGRectMake(50, 100, 350, 500);    

    datePicker.datePickerMode = UIDatePickerModeCountDownTimer;

    datePicker.countDownDuration = 5 * 60; //初始设置为5分钟
    //每隔一分钟调用一次
    timer = [NSTimer timerWithTimeInterval:60 target:self selector:@selector(timerAction:) userInfo:nil repeats:YES];
    NSRunLoop * runLoop = [NSRunLoop currentRunLoop];
    [runLoop addTimer:timer forMode:NSDefaultRunLoopMode];

}

- (void) timerAction:(id) sender {
    NSTimeInterval now = datePicker.countDownDuration;
    if (0 < now) {
        datePicker.countDownDuration -= 60;
    }
}

每隔一分钟，跳动一次：