Question

我正在使用NSUserDefaults来保存BOOL，这些BOOL表示映射的注释是否是“最喜欢的”。当用户退出应用程序然后重新启动它时，BOOL正确保存。但是，当用户强制退出（按两次主页按钮并在应用程序上向上滑动）应用程序时，NSUserDefaults将丢失。有人可以解释为什么会这样吗？我正在使用Xcode v7.0。

-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {

// If annotation is displayed, the User can save/clear annotation as a favorite
if ((_acmeMotorsIsDisplayed == YES) && (_acmeMotorsIsFavorite == YES)){
            _acmeMotorsIsFavorite = NO;
            [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"acmeMotorsIsFavorite"];
        }
else if ((_acmeMotorsIsDisplayed == YES) && (_acmeMotorsIsFavorite == NO)){
            _acmeMotorsIsFavorite = YES;
            [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"acmeMotorsIsFavorite"];
        }
}

-(void)loadUserDefaults{
// One of many lines of code that load user default settings
_acmeMotorsIsFavorite = [[NSUserDefaults standardUserDefaults] boolForKey:@"acmeMotorsIsFavorite"];
}

-(void)viewDidLoad {
    [self loadUserDefaults];
}

Answer 1

我认为你忘记了synchronize方法。

NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
[userDefaults setBool:NO forKey:@"acmeMotorsIsFavorite"];
[userDefaults synchronize];

Answer 2

当用户双击Home时，调用app delegate方法applicationWillResignActive:，此时同步NSUserDefaults：

- (void)applicationWillResignActive:(UIApplication *)application {
    [[NSUserDefaults standardUserDefaults] synchronize];
}

应用程序强制退出时，Xcode NSUserDefaults设置丢失

2 个答案: