Autolayoutでキーボードの高さによってViewを調整する方法(Objective-C版)

gistfile1.m

// ↓ここで紹介されていたSwiftのコードをObjective-Cに置き換えたものです。
//
// Autolayoutでキーボードの高さによってViewを調整する方法
// http://blog.tsumikiinc.com/article/20150123_autolayout-view.html
//
// StoryboardでUITextViewのBottomのVertical Space ConstraintとbottomLayoutConstraintを接続する必要があります。
// 詳細は元のBlog記事を参照ください。


@property (nonatomic, weak) IBOutlet NSLayoutConstraint *bottomLayoutConstraint;

// 〜

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillChangeFrame:) name:UIKeyboardWillChangeFrameNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}

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

- (void)keyboardWillChangeFrame:(NSNotification *)aNotification
{
    CGRect keyBoardFrame = [[[aNotification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

    NSTimeInterval duration = [[[aNotification userInfo] objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];

    self.bottomLayoutConstraint.constant = keyBoardFrame.size.height;
    
    [UIView animateWithDuration:duration animations:^{
        [self.view layoutIfNeeded];
    }];
}
- (void)keyboardWillHide:(NSNotification *)aNotification
{
    NSTimeInterval duration = [[[aNotification userInfo] objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];

    self.bottomLayoutConstraint.constant = 0;
    
    [UIView animateWithDuration:duration animations:^{
        [self.view layoutIfNeeded];
    }];
}