下面的applicationWillTerminate 保存started、stopped、startTime 和stopTime 的状态并使定时器失效。目的是能够终止应用程序，然后在应用程序重新启动时恢复状态和重新启动计时器。
//Save status to file on applicationWillTerminate.
- (void)applicationWillTerminate:(UIApplication *)application {
NSMutableArray *status = [[NSMutableArray alloc] init];
[status addObject:startTime];
[status addObject:stopTime];
[status addObject:[NSNumber numberWithInteger: started]];
[status addObject:[NSNumber numberWithInteger: stopped]];
[status writeToFile:[self statusFilePath] atomically:YES];
[status release];
if ([timer isValid]) {
[timer invalidate];
}
[lblTimer release];
[txtDescription release];
[lblDriverName release];
[startTime release];
[stopTime release];
// [timer release];
// timer = nil;
}
下面的 viewDidLoad 恢复状态，应该在满足 if 条件时重新启动计时器。
- (void)viewDidLoad {
// Re-direct applicationWillTerminate.
UIApplication *driverApp = [UIApplication sharedApplication];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(applicationWillTerminate:)
name:UIApplicationWillTerminateNotification
object:driverApp];
// Initialize status for first run, over-ride for saved status.
NSString *statusPath = [self statusFilePath];
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:statusPath];
if (fileExists) {
// Over-ride for status saved.
NSArray *values = [[NSArray alloc] initWithContentsOfFile:statusPath];
startTime = [values objectAtIndex:0];
stopTime = [values objectAtIndex:1];
started = [[values objectAtIndex:2] intValue];
stopped = [[values objectAtIndex:3] intValue];
[values release];
}
else {
// For first run.
started = 0;
stopped = 0;
}
// Restart timer if previously still running.
if (started == 1 && stopped == 0) {
if (![timer isValid]) {
timer = [NSTimer scheduledTimerWithTimeInterval:0.25
target:self
selector:@selector(updateTimer)
userInfo:nil
repeats:YES];
}
}
[super viewDidLoad];
}
程序第一次在模拟器中运行正常。在第二次模拟器运行时，应用程序在达到计时器时崩溃 = [NSTimer......repeats:YES]; 陈述。我研究并尝试了很多东西都无济于事。
任何提示将不胜感激。