1.注冊監聽鍵盤事件的通知

代碼如下：

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
   
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardShow:)
                                                 name:UIKeyboardDidShowNotification
                                               object:nil];
   
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
   
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardHide:)
                                                 name:UIKeyboardDidHideNotification
                                               object:nil];

2.在鍵盤將要出現和隱藏的回調中，加入動畫

代碼如下：

- (void)keyboardWillShow:(NSNotification *)notif {
    if (self.hidden == YES) {
        return;
    }
   
    CGRect rect = [[notif.userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGFloat y = rect.origin.y;
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.25];
    NSArray *subviews = [self subviews];
    for (UIView *sub in subviews) {
       
        CGFloat maxY = CGRectGetMaxY(sub.frame);
        if (maxY > y - 2) {
            sub.center = CGPointMake(CGRectGetWidth(self.frame)/2.0, sub.center.y - maxY + y - 2);
        }
    }
    [UIView commitAnimations];
}

- (void)keyboardShow:(NSNotification *)notif {
    if (self.hidden == YES) {
        return;
    }
}

- (void)keyboardWillHide:(NSNotification *)notif {
    if (self.hidden == YES) {
        return;
    }
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.25];
    NSArray *subviews = [self subviews];
    for (UIView *sub in subviews) {
        if (sub.center.y < CGRectGetHeight(self.frame)/2.0) {
            sub.center = CGPointMake(CGRectGetWidth(self.frame)/2.0, CGRectGetHeight(self.frame)/2.0);
        }
    }
    [UIView commitAnimations];
}

- (void)keyboardHide:(NSNotification *)notif {
    if (self.hidden == YES) {
        return;
    }
}

3.監聽鍵盤刪除鍵之非代理實現
在UITextField 和 UITextView ，如何監聽到刪除鍵。

我看到網上都是用代理監聽的，我覺得不靠譜。

其實蘋果已經寫的很清楚了。

就在他們實現的協議裡面～～
代碼如下：

NS_CLASS_AVAILABLE_IOS(2_0) @interface UITextView : UIScrollView<UITextInput>
@protocol UITextInput<UIKeyInput>
@protocol UIKeyInput <UITextInputTraits>

- (BOOL)hasText;

- (void)insertText:(NSString *)text;

- (void)deleteBackward;

@end

寫的非常清楚，一看就明白。

－deleteBackward 這個方法就是刪除按鈕監聽。

只要自己寫個子類，重寫此方法就能監聽。