问ios如何获取App上线时间？

EN

- (void)applicationDidEnterBackground:(UIApplication *)application {
// save the last app opening time, you can save in NSuserdefaults also
startDate = [NSDate date]; 
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
NSDate *now = [NSDate date];
// Returns in seconds
NSTimeInterval timeInterval = [now timeIntervalSinceDate:startDate]

if(timeInterval > (24*3600)) {
          // remind the user of updating App here.
    }
}

 NSDate *dateTimenow=[NSDate date];
NSDateFormatter *dateFormatter=[[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"dd-MM-yyyy hh:mm"];
NSString *strDateTimeNow=[NSString stringWithFormat:@"%@",[dateFormatter stringFromDate:dateTimenow]];
NSLog(@"now date time: %@",strDateTimeNow);

NSUserDefaults *userdefaults=[NSUserDefaults standardUserDefaults];

if ([userdefaults valueForKey:@"LastAppLaunchTime"]) {
    NSString *strPreviousDateTime=[NSString stringWithFormat:@"%@",[userdefaults valueForKey:@"LastAppLaunchTime"]];
    NSLog(@"previous date time: %@",strPreviousDateTime);

    //Now you can compare current date time with previous date time
    //perform task after comparing



}


[userdefaults setValue:strDateTimeNow forKey:@"LastAppLaunchTime"];// saving recent date time details for next time

NSDate* now = [NSDate date];

if ([now timeIntervalSinceDate:lastTimeOpened] > someTime)