NSUserDefaults 没有快速更新值

Question

我有超时功能，如果应用程序空闲（在后台）一段时间，我会超时我的应用程序并将用户发送到登录屏幕。我在我的应用程序委托中将用户默认值中的“timedOut”键设置为 YES，然后在每个视图控制器中引用该键，如果是，我会转到登录屏幕。在登录屏幕上，如果“timedOut”为“是”，我有一个显示“会话已超时”的标签。我的问题是，如果我登录，然后很快注销，标签就会显示，即使我在显示标签后立即将该键明确设置为 NO，然后同步用户默认值。 如果我等待一两秒然后退出，标签会按原样隐藏。我已经解决了“问题”，但想了解行为。

视图中的代码确实加载到了我的登录视图控制器中。您会认为这会将 isTimedOut 更改为 NO，但是当我快速注销时，再次调用 viewdidload，但 isTimedOut 为 YES。

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
sessionLabel.hidden = YES;
isTimedOut = [defaults boolForKey:@"isTimedOut"];
if (isTimedOut == YES)
{
    sessionLabel.hidden = NO;
    defaults = [NSUserDefaults standardUserDefaults];
    [defaults setBool:NO forKey:@"isTimedOut"];
    isTimedOut = NO;
    NSLog(@"Timed Out has been reset to %s",[defaults boolForKey:@"isTimedOut"] ? "YES" : "NO");
    [defaults synchronize];

}

更新

我使用我的应用程序委托中的属性而不是 NSUserDefaults 替换了上面的代码，并且“奇怪”的行为消失了。

eONavAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
isTimedOut = appDelegate.isTimedOut;
sessionLabel.hidden = YES;
//isTimedOut = [defaults boolForKey:@"isTimedOut"];
  NSLog(@"Timed Out has been reset to %s",appDelegate.isTimedOut ? "YES" : "NO");
if (isTimedOut == YES)
{
    appDelegate.isTimedOut = NO;
    sessionLabel.hidden = NO;

}

更多代码

要注销，我有 UIButtonBarItem 以编程方式调用 segue。 doLogout 属性告诉登录视图控制器运行注销 API。

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Make sure your segue name in storyboard is the same as this line
if ([[segue identifier] isEqualToString:@"logoutSegue"])
{

    // Get reference to the destination view controller
    eoLoginViewController *vc = [segue destinationViewController];
    vc.doLogout = YES;

}
} 

isTimedOut 设置在应用委托中的一个位置。

-(void)timeoutWithDate:(NSDate *)currentDate
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSDate *previousDate  = [defaults objectForKey:@"enteredBackground"];
NSTimeInterval distanceBetweenDates = [currentDate timeIntervalSinceDate:previousDate];//TimeInterval is in seconds
NSLog(@"Time between dates in seconds %f",distanceBetweenDates);

double minutesInAnHour = 60;
double minutesBetweenDates = distanceBetweenDates / minutesInAnHour;
NSLog(@"minutesBetweenDates %f",minutesBetweenDates);


if(minutesBetweenDates > 60)
{
    isTimedOut = YES;

}
else
{
    isTimedOut = NO;
}

}

Answer 1

使用这个：

保存布尔值：

[[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"isTimedOut"];

加载一个布尔值：

    if ([[NSUserDefaults standardUserDefaults] boolForKey:@"isTimedOut"] == YES) {
        //it equals yes
        }

    else {
        //it equals no
        }

Answer 2

你为什么不尝试这样的事情呢？我没有看到你的完整项目，但它应该很有魅力。

- (void)viewDidLoad {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillResignActive:) name:UIApplicationWillResignActiveNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillEnterForeground:) name:UIApplicationWillEnterForegroundNotification object:nil];
}

那么……

- (void)applicationWillResignActive:(UIApplication *)application
{
    [[NSUserDefaults standardUserDefaults] setValue:[NSDate date] forKey:@"sleepTime"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

还有……

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    NSInteger _timeoutInSeconds = 300;

    NSDate *_sleepTime = [[NSUserDefaults standardUserDefaults] valueForKey:@"sleepTime"];
    if (_sleepTime) {
        NSCalendar *_calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
        NSDateComponents *_dateComponents = [_calendar components:NSSecondCalendarUnit fromDate:_sleepTime toDate:[NSDate date] options:0];
        if (_dateComponents.second > _timeoutInSeconds) {
            // expired session
        } else {
            // valid session
        }
    }
}