iOSでキーボードのアニメーションを止める方法

iOSのアプリでキーボードの出現や消滅のアニメーションを止めると、動作がキビキビになります。その方法を共有します。

ObjectiveC

@interface ViewController : UIViewController
@end

@implementation ViewController
-(void) viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardDidShow:)
                                                 name:UIKeyboardDidShowNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardDidHide:)
                                                 name:UIKeyboardDidHideNotification
                                               object:nil];
}

-(void) viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:UIKeyboardWillShowNotification
                                                  object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:UIKeyboardDidShowNotification
                                                  object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:UIKeyboardWillHideNotification
                                                  object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:UIKeyboardDidHideNotification
                                                  object:nil];
}

static BOOL needRevert;

-(void) keyboardWillShow:(NSNotification*)notif
{
    needRevert = [UIView areAnimationsEnabled];
    [UIView setAnimationsEnabled:NO];
}

-(void) keyboardDidShow:(NSNotification*)notif
{
    if (needRevert) [UIView setAnimationsEnabled:YES];
}

- (void)keyboardWillHide:(NSNotification*)notif
{
    needRevert = [UIView areAnimationsEnabled];
    [UIView setAnimationsEnabled:NO];
}

- (void)keyboardDidHide:(NSNotification*)notif
{
    if (needRevert) [UIView setAnimationsEnabled:YES];
}

@end