004-实现点击任意屏幕上非文本框点移除键盘

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    [self setUpForDismissKeyboard];
}
- (void)setUpForDismissKeyboard {
    NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
    UITapGestureRecognizer *singleTapGR =
    [[UITapGestureRecognizer alloc] initWithTarget:self
                                            action:@selector(tapAnywhereToDismissKeyboard:)];
    NSOperationQueue *mainQuene =[NSOperationQueue mainQueue];
    [nc addObserverForName:UIKeyboardWillShowNotification
                    object:nil
                     queue:mainQuene
                usingBlock:^(NSNotification *note){
                    [self.view addGestureRecognizer:singleTapGR];
                }];
    [nc addObserverForName:UIKeyboardWillHideNotification
                    object:nil
                     queue:mainQuene
                usingBlock:^(NSNotification *note){
                    [self.view removeGestureRecognizer:singleTapGR];
                }];
}

- (void)tapAnywhereToDismissKeyboard:(UIGestureRecognizer *)gestureRecognizer {
    //此method会将self.view里所有的subview的first responder都resign掉
    [self.view endEditing:YES];
}