UIDatePicker不會更改值

Question

我里面有UIDatePicker UIViewController 。 我將UIDatePicker與標頭類中的IBOutlet屬性連接，因為我在應用程序中使用情節提要：

#import <UIKit/UIKit.h>
@protocol CreationDateDelegate <NSObject>
@optional
    -(void)selectedDateIs:(NSString*)dateValue;
@end

@interface SelectCreationDateViewController : UIViewController
{
    IBOutlet UIDatePicker *datePicker;
}
@property (nonatomic,assign)id<CreationDateDelegate>creationDateDelegate;
@property (nonatomic,retain) IBOutlet UIDatePicker *datePicker;

@end

-.m -----

#import "SelectCreationDateViewController.h"
@interface SelectCreationDateViewController ()
{
    NSString *dateFromString;
}
@end

@implementation SelectCreationDateViewController
@synthesize creationDateDelegate,datePicker;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) 
    {
    }
    return self;
}

- (void)viewDidLoad
{   
    self.title = @"Select creation date";
    [super viewDidLoad];

    [datePicker setHidden:NO];
    datePicker.timeZone = [NSTimeZone localTimeZone];
    [datePicker setDatePickerMode:UIDatePickerModeDate];

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

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

-(void)viewWillDisappear:(BOOL)animated{
    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    NSString *dateFromString = [formatter stringFromDate:datePicker.date];
    [self.creationDateDelegate selectedDateIs:dateFromString];
}

-(void)changeValueOfDatePicker:(id)sender{
    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    dateFromString = [formatter stringFromDate:datePicker.date];
    [self.creationDateDelegate selectedDateIs:dateFromString];
    NSLog(@"Date from string value equal %@",dateFromString);
}
@end

為什么每次更改DatePicker的值時返回的值都不會更改？ 有任何想法嗎？ 另外，讓我知道我是否在代碼中犯了任何錯誤。

Answer 1

通過添加以下代碼行對其進行修復 ：

僅當您使用iOS7時-in方法（void）viewDidLoad方法

[self.datePicker setDate:[NSDate date] animated:YES];

Answer 2

還設置一些dateformate

 -(void)changeValueOfDatePicker:(id)sender{

        NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
        [formatter setDateFormat:@"yyyy-MM-dd HH:mm"];

        dateFromString = [formatter stringFromDate:datePicker.date];
        [self.creationDateDelegate selectedDateIs:dateFromString];
        NSLog(@"Date from string value equal %@",dateFromString);
    }