objective-c - 从 NSUserDefaults 检索数据 - 在一个 View 中有效，但在另一个 View 中失败

Question

我使用下面的代码(来自 AppDelegate 文件)将登录的 Facebook 用户名保存到 NSUserDefaults 首选项。该代码检索用户名并将其输出到控制台就好了。当我尝试在另一个 View Controller 中做同样的事情时，NSLog 输出返回(null)。

我错过了什么？谢谢你的帮助。

- (void)request:(FBRequest *)request didLoad:(id)result {
    if ([result isKindOfClass:[NSDictionary class]]) {
        NSDictionary* hash = result;
        NSString *username = (NSString*)[hash valueForKey:@"name"];
        [[NSUserDefaults standardUserDefaults] setObject:username forKey:@"Username"];
        NSLog(@"%@", username);
        NSUserDefaults * standardUserDefaults = [NSUserDefaults standardUserDefaults];
        NSString *user = [standardUserDefaults stringForKey:@"Username"];
        NSLog(@"username from user defs %@",user);
    }
};

这是来自其他 View Controller 的代码不起作用:

NSUserDefaults * standardUserDefaults = [NSUserDefaults standardUserDefaults];
NSString *user = [standardUserDefaults stringForKey:@"Username"];
NSLog(@"username from user defs %@",user);
userNameLbl.text = user;

这是日志输出:

username from user defs app delegate my Facebook name
2012-03-30 13:29:20.564 project V2[63339:15803] (null)
2012-03-30 13:29:20.565 project V2[63339:15803] username from user defs app delegate (null)
2012-03-30 13:29:28.620 project V2[63339:15803] username from user defs (null)

Answer 1

NSUserDefaults * standardUserDefaults = [NSUserDefaults standardUserDefaults];
NSString *user = [[NSUserDefaults standardUserDefaults] stringForKey:@"Username"];
NSLog(@"username from user defs %@",user);
userNameLbl.text = user;

试试这个(我只改变了一行)

NSString *user = [[NSUserDefaults standardUserDefaults] stringForKey:@"Username"];

编辑
这就是我将内容保存到 NSUserDefaults 的方式；

NSString *theKeyIWantToSave;
NSUSerDefaults *defaults=[NSUserDefaults standardUserDefaults];
[defaults setObject:theKeyIWantToSave forKey:@"SomeKey"];

随时随地我想检索它

NSString *key=[[NSUserDefaults standardUserDefaults] objectForKey:@"SomeKey"];