UIKeyBoardWIllShowNotification调用一次的原因是什么？

Question

我正在使用keyboardWasShown和keyboardWillBeHidden通知滑动视图以获得可见的文本视图.

我有一个UITabBar带有六个标签的应用程序.

在每个视图中我都在使用UINavigationController.

在每个UITableViewCell我使用键盘通知的详细视图中.

所以问题是键盘通知是我第一次使用.在其他选项卡上它将无法正常工作.

代码如下:

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWasShown:)
                                             name:UIKeyboardDidShowNotification
                                           object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWasHidden:)
                                             name:UIKeyboardDidHideNotification
                                           object:nil];

和方法

- (void)keyboardWasShown:(NSNotification *)aNotification {
    if ( keyboardShown )
        return;


        NSDictionary *info = [aNotification userInfo];
        NSValue *aValue = [info objectForKey:UIKeyboardBoundsUserInfoKey];
        CGSize keyboardSize = [aValue CGRectValue].size;

        NSTimeInterval animationDuration = 0.300000011920929;
        CGRect frame = self.view.frame;
        frame.origin.y -= keyboardSize.height-100;
        frame.size.height += keyboardSize.height-100;
        [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
        [UIView setAnimationDuration:animationDuration];
        self.view.frame = frame;
        [UIView commitAnimations];

    viewMoved = YES;

    keyboardShown = YES;
}
- (void)keyboardWasHidden:(NSNotification *)aNotification {
    if ( viewMoved  && tvAddreview) {
        NSDictionary *info = [aNotification userInfo];
        NSValue *aValue = [info objectForKey:UIKeyboardBoundsUserInfoKey];
        CGSize keyboardSize = [aValue CGRectValue].size;

        NSTimeInterval animationDuration = 0.300000011920929;
        CGRect frame = self.view.frame;
        frame.origin.y += keyboardSize.height-100;
        frame.size.height -= keyboardSize.height-100;
        [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
        [UIView setAnimationDuration:animationDuration];
        self.view.frame = frame;
        [UIView commitAnimations];

        viewMoved = NO;
    }

    keyboardShown = NO;
}

Answer 1

你应该在eachClass中像这样:

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

    NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
    [nc addObserver:self 
           selector:@selector(keyboardWasShown:) 
               name:UIKeyboardWillShowNotification 
             object:nil];
    [nc addObserver:self 
           selector:@selector(keyboardWasHidden:) 
               name:UIKeyboardWillHideNotification 
             object:nil];

}

- (void) viewWillDisappear: (BOOL)animated{

    [super viewWillDisappear:animated];

    NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
    [nc removeObserver:self 
                  name:UIKeyboardWillShowNotification 
                object:nil];
    [nc removeObserver:self 
                  name:UIKeyboardWillHideNotification 
                object:nil];
}

因为通知是在应用程序级别而不是您的类级别.因此,如果您已将它们添加到一个类而不是所有类中,那么请转到下一个类.通知仍将keyboardWasShown:从您添加通知的类调用密钥和另一个,因此您的本地变量如... viewMoved = YES;

keyboardShown = YES;

会抛出坏的超额例外

在您的情况下,还需要在所有6个视图控制器中执行此操作

希望这可以帮助.