iphone - iOS 应用程序 : Should show a specific image at a specific day, 但崩溃

Question

我是开发 iOS 应用程序的新手，英语不是我的母语，所以请原谅我的任何错误和丑陋的代码。

我尝试创建的应用程序应该只在特定的一天显示一张特定的图像(如果日期更改，则更改图像)。因此我实现了一个检查日期的无限循环。如果它与上次更改的图像不同，则图像会再次更改。图像以“YearMonthDay.png”方案命名(例如“20131017.png”)。

我已经在 google 上搜索了很多并整理了一些代码(我知道它很丑)，但每次都会崩溃。

如果有任何帮助，我将不胜感激!

smViewController.h:

#import <UIKit/UIKit.h>

@interface smViewController : UIViewController {
  UIImageView* mImageView;
}

@property (nonatomic, retain) IBOutlet UIImageView* imageView;

- (IBAction)contentModeChanged:(UISegmentedControl*)segmentedControl;

@end

smViewController.m

#import "smViewController.h"

@interface smViewController ()

@end

@implementation smViewController
@synthesize imageView = mImageView;

- (void)viewDidUnload
{
    self.imageView = nil;
    [super viewDidUnload];
}

- (void)dealloc
{
    [mImageView release];
    [super dealloc];
}
- (void)viewDidLoad
{
    [super viewDidLoad];

    NSString *oldDateString = @"";

    while(true)
    {
        NSDate *today = [NSDate date];
        NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
        [dateFormat setDateFormat:@"yyyy/MM/dd"];
        NSString *dateString = [dateFormat stringFromDate:today];
        NSLog(@"date: %@", dateString);
        if([dateString isEqualToString: oldDateString])
        {
        }
        else
        {
            NSAssert(self.imageView, @"self.imageView is nil. Check your IBOutlet   connections");
            UIImage* image = [UIImage imageNamed:dateString];
            NSAssert(image, @"image is nil. Check that you added the image to your bundle and that the filename above matches the name of you image.");
            self.imageView.backgroundColor = [UIColor whiteColor];
            self.imageView.clipsToBounds = YES;
            self.imageView.image = image;
            oldDateString = dateString;
        }
        [dateFormat release];
    }
}

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

@end

Answer 1

您应该在您的应用程序 UIApplicationDelegate 中覆盖 - (void)applicationSignificantTimeChange:(UIApplication *)application。然后您将在日期更改时收到一个事件，您可以删除任何循环或计时器。