UIDatepicker 和 NSDate 之间的日期差异

Question

我有一个日期选择器，并将值保存到 .plist 文件，其中包含字符串格式的 UserDate 键。

datepicker 返回的值采用 2013-02-13 11:17:34 +0000 格式。

为了将其保存到 .plist 文件中，我需要将 datepicker 转换为字符串 2013-02-14T19:17:34Z

在其他视图中，我想从 plist 检索 UserDate 并与用户当前日期。我想要不同的日子和时间。

我将 2012-02-12 19:17:34 +0800 转换并传递为 destinationDate 以与 [NSDate new] 进行比较。 我设法计算了两个日期之间的差异。但结果不正确。

如何获得iPhone日期和Datepicker日期之间两个日期的正确差异结果？我需要使用特定时区吗？

额外信息：我住在 GMT+8。我将模拟器日期选择器设置为2012年2月13日，但结果仍然显示倒计时有18小时4分钟。

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
int units = NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

NSDateComponents *components = [calendar components:units fromDate:[NSDate date] toDate:destinationDate options:0];
[datelabel setText:[NSString stringWithFormat:@"%d%c %d%c %d%c %d%c %d%c", [components month], 'm', [components day], 
                    'd', [components hour], 'h', [components minute], 'm', [components second], 's']];

NSLog

编辑

Plist 文件。

保存方法

NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
// get documents path
NSString *documentsPath = [paths objectAtIndex:0];
// get the path to our Data/plist file
NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"Data.plist"];

// set the variables to the values in the text fields
self.userTitle = myTitle.text;
self.userMessage = myMessage.text;  

NSLog(@"METHOD SAVE");

NSLog(@"Datepicker value =  %@", myDate.date );

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setFormatterBehavior:NSDateFormatterBehavior10_4];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss'Z'"];
NSString *mdate = [dateFormatter stringFromDate:myDate.date];
//  [dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss'Z'"];

NSLog(@"Converted from date picker, save into plist =  %@", mdate );

self.saveDate = mdate;
//self.userDate = myDate.date;

// create dictionary with values in UITextFields
NSDictionary *plistDict = [NSDictionary dictionaryWithObjects: [NSArray arrayWithObjects: userTitle, userMessage, saveDate, nil] forKeys:[NSArray arrayWithObjects: @"Title", @"Message", @"UserDate", nil]]; NSString *error = nil;
// create NSData from dictionary
NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:plistDict format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];

// check is plistData exists
if(plistData)
{
    // write plistData to our Data.plist file
    [plistData writeToFile:plistPath atomically:YES];
    
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Success" message:@"Your settings have been saved." delegate:self cancelButtonTitle:nil otherButtonTitles:@"Ok",nil];
    [alert show];
}
else
{
    NSLog(@"Error in saveData: %@", error);
    //[error release];
}

viewWillAppear

- (void)viewWillAppear:(BOOL)animated {
[self.navigationController setNavigationBarHidden:YES];

[super viewWillAppear:animated];

// Data.plist code
// get paths from root direcory
NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
// get documents path
NSString *documentsPath = [paths objectAtIndex:0];
// get the path to our Data/plist file
NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"Data.plist"];

// check to see if Data.plist exists in documents
if (![[NSFileManager defaultManager] fileExistsAtPath:plistPath])
{
    // if not in documents, get property list from main bundle
    plistPath = [[NSBundle mainBundle] pathForResource:@"Data" ofType:@"plist"];
}

// read property list into memory as an NSData object
NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:plistPath];
NSString *errorDesc = nil;
NSPropertyListFormat format;
// convert static property liost into dictionary object
NSDictionary *temp = (NSDictionary *)[NSPropertyListSerialization propertyListFromData:plistXML mutabilityOption:NSPropertyListMutableContainersAndLeaves format:&format errorDescription:&errorDesc];
if (!temp)
{
    NSLog(@"Error reading plist: %@, format: %d", errorDesc, format);
}

NSLog(@"Plist Title: %@", [temp objectForKey:@"Title"]);
NSLog(@"Plist Message: %@", [temp objectForKey:@"Message"]);
NSLog(@"Plist date: %@", [temp objectForKey:@"UserDate"]);

userTitle.text = [NSString localizedStringWithFormat:@"%@", [temp objectForKey:@"Title"]];
userMessage.text = [NSString localizedStringWithFormat:@"%@", [temp objectForKey:@"Message"]];

//http://stackoverflow.com/questions/1070354/how-do-i-get-the-current-date-in-cocoa

NSDate* now = [[NSDate alloc] initWithTimeIntervalSinceNow:3600];
userCoundown.text = [NSString stringWithFormat:@"%@",now];  

NSString *uDate = [[NSString alloc] init];
uDate = [temp objectForKey:@"UserDate"];
NSLog(@"Plist date in string - %@", uDate);

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setFormatterBehavior:NSDateFormatterBehavior10_4];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss'Z'"];
NSDate *ddate = [dateFormatter dateFromString:uDate];
[dateFormatter setDateFormat:@"yyyy-MM-dd H:mm:ss Z"];

NSLog(@"Format date from Plist -  %@", [dateFormatter stringFromDate:ddate]);

//NSLog(@"GMT format from Plist - %@", timeStamp);

//http://www.epochconverter.com/#
destinationDate = ddate;
timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateLabel) userInfo:nil repeats:YES];
}

updatelabel

-(void)updateLabel {

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
int units = NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

NSDateComponents *components = [calendar components:units fromDate:[NSDate date] toDate:destinationDate options:0];
[datelabel setText:[NSString stringWithFormat:@"%d%c %d%c %d%c %d%c %d%c", [components month], 'm', [components day], 
                    'd', [components hour], 'h', [components minute], 'm', [components second], 's']];
}

Answer 1

NSDate 保持 GMT 时间。如果您有时区，则必须指定它们。

问题不清楚，所以这不是一个完整的答案，但应该为 plist 中的 NSDate 提供一些帮助。

以下是使用 NSDate 创建、写入和读取 plist 的示例：

NSDictionary *plistDict = [NSDictionary dictionaryWithObjectsAndKeys:
                           userTitle,   @"Title",
                           userMessage, @"Message",
                           saveDate,    @"UserDate",
                           nil];

[plistDict writeToFile:filePath atomically:YES];

NSDictionary *plistDictRead = [NSDictionary dictionaryWithContentsOfFile:filePath];
NSDate *dateRead = [plistDictRead objectForKey:@"UserDate"];

无需将 NSDate 转换为字符串，也无需使用 NSPropertyListSerialization。

Answer 2

请记住创建 NSDate，然后使用有效的时区和日历输出它！

查看我在另一篇文章中回答的类似问题：
UIDatePicker 返回错误的 NSDate