Summary of code instances listening for keyboard events in iOS application development

1. Register to listen for notifications of keyboard events

    [[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. Add animation to keyboard callbacks to appear and hide

- (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. Monitor the non-proxy implementation of the keyboard delete key
In UITextField and UITextView, how to listen for the delete key.

I see the Internet is using proxy monitoring, I feel unreliable.

Apple has made that clear.

It's in the protocol that they implemented

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

It's written very clearly, so you can see the 1.

-deleteBackward is the delete button listener.

You can override this method by subclassing it yourself.