iphone - 键盘触发通知以及默认通知

Question

我的 ViewController 中有这段代码:

- (void) viewWillAppear :(BOOL)animated {
     // register for keyboard notifications
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWasShown:) 
           name:UIKeyboardDidShowNotification object:nil];
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillBeHidden:) 
           name:UIKeyboardWillHideNotification object:self.view.window];

     // register for defaults change notification
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(defaultsChanged:)      
           name:NSUserDefaultsDidChangeNotification object:nil];
 }

 -(void) viewWillDisappear :(BOOL)animated {
     [[NSNotificationCenter defaultCenter] removeObserver:self];
 }

问题是当键盘出现时，defaultsChanged 方法也会被触发。

当键盘出现时，这是调用顺序(从日志中摘录):

start defaultsChanged 
end   defaultsChanged
start textFieldDidBeginEdit
end   textFieldDidBeginEdit
start keyboardWasShown
end   keyboardWasShown

我不知道会发生什么。大家有什么想法吗？

Answer 1

也许默认值确实因为显示键盘的副作用而发生了变化？为什么不打印之前和之后的默认值，看看是否有任何变化？下面是一些使用 NSLog 打印 NSUserDefaults 的代码:

NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
NSDictionary* defaultsDict = [defaults dictionaryRepresentation];
NSLog(@"defaults = %@", defaultsDict);