ios - UIKeyboardWillShowNotification 从堆栈中的下一个类错误地调用

Question

我检测到键盘何时会显示以下代码。但是，当我使用 pushViewController 推送到另一个屏幕并在该屏幕中打开键盘时，keyboardWillShow 被调用！这真的正确吗？

[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillShow:) 
                                             name:UIKeyboardWillShowNotification 
                                           object:nil];
// register for keyboard notifications
[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillHide:) 
                                             name:UIKeyboardWillHideNotification 
                                           object:nil];

Answer 1

是的，这是正确的行为。由于推送另一个视图的视图仍然存在并且通知是应用程序范围的。

您可以在以下位置删除通知：

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];

    [[NSNotificationCenter defaultCenter] removeObserver:self 
                                                    name:UIKeyboardWillShowNotification 
                                                  object:nil];

    [[NSNotificationCenter defaultCenter] removeObserver:self 
                                                    name:UIKeyboardWillHideNotification 
                                                  object:nil];
}

如果你想设置观察者，然后将代码从 viewDidLoad 放置到 viewWillAppear:(BOOL)animated：

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillShow:) 
                                             name:UIKeyboardWillShowNotification 
                                           object:nil];
    // register for keyboard notifications
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillHide:) 
                                             name:UIKeyboardWillHideNotification 
                                           object:nil];
}