UIDatePicker

#import "AppDelegate.h"

@interface AppDelegate ()
@property (nonatomic,strong)UILabel *label;
@end

@implementation AppDelegate

- (void)dealloc
{
    self.label = nil;
    self.window = nil;
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    
    UIDatePicker *picker = [[UIDatePicker alloc] initWithFrame:CGRectZero];
    picker.datePickerMode = UIDatePickerModeDateAndTime;
    // 添加事件
    [picker addTarget:self action:@selector(changeDateOfPicker:) forControlEvents:UIControlEventValueChanged];
    [self.window addSubview:picker];
    // 创建label
    self.label = [[UILabel alloc] initWithFrame:CGRectMake(0, 300, [UIScreen mainScreen].bounds.size.width, 100)];
    self.label.backgroundColor = [UIColor clearColor];
    self.label.textAlignment = NSTextAlignmentCenter;
    [self.window addSubview:self.label];
    
    [self.window makeKeyAndVisible];
    return YES;
}

- (void)changeDateOfPicker:(UIDatePicker *)sender
{
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"Y/MM/dd H:mm:ss"];
    NSString *dateString = [dateFormatter stringFromDate:[sender date]];
    
    self.label.text = dateString;
}


@end