IOS: store an array with NSUserDefault

问题:

I want to store an array with NSUserDefault, then, I put in applicationDidEnterBackground

[[NSUserDefaults standardUserDefaults] setObject:myArray forKey:@"myArray"];

and in application didFinishLaunchingWithOption

myArray= [[NSMutableArray alloc] 
          initWithArray:[[NSUserDefaults standardUserDefaults] 
           objectForKey:@"myArray"]];

it's ok for multitasking device, but for not-multitasking device, how can I solve?

回答1:

Store the object in NSUserDefaults in -applicationWillTerminate:, if it hasn't already been saved by the invocation of -applicationDidEnterBackground: (i.e. check if multitasking is supported, if it is, then don't save it because it's already been saved.)

- (void) applicationWillTerminate:(UIApplication *) app {
    if([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)] &&
       ![[UIDevice currentDevice] isMultitaskingSupported]) {
       [[NSUserDefaults standardUserDefaults] setObject:myArray forKey:@"myArray"];
    }
}

回答2:

Do not forget to sync the buffer before going into background:

[[NSUserDefaults standardUserDefaults] synchronize];

回答3:

The previous answers are all correct, but note that neither applicationDidEnterBackground nor applicationWillTerminate are guaranteed to be called in all situations. You are usually better off storing important data whenever it has changed.

回答4:

Save NSUserDefaults at

- (void)applicationWillTerminate:(UIApplication *)application 

回答5:

set

[[NSUserDefaults standardUserDefaults] setObject:myArray forKey:@"myArray"];

in

applicationWillTerminate

回答6:

and don't forget to use the encodeWithCoder and initWithCoder inside the object that you are trying to save and that is contained in the array