当键盘出现时调整 UITextView 的大小

我想在键盘出现时调整文本视图的大小。我的代码如下。我打开了自动布局，因此使用来自超级视图的 textView->bottom 空间的约束，并通过 IBOutlet distanceFromBottom 引用它。

- (void)keyboardWillShow:(NSNotification *)notification
{
  [UIView animateWithDuration:0.3 animations:^{
    NSDictionary* d = [notification userInfo];
    CGRect r = [d[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    r = [textView convertRect:r fromView:Nil];
    if(IS_IPHONE_6||IS_IPHONE_6P)
      distanceFromBottom.constant = r.origin.y+78;
    else if(IS_IPHONE_5)
      distanceFromBottom.constant = r.origin.y+183;
  }];
}

上面的代码完美运行。我不明白的是为什么我需要为iPhone6添加+78或为iPhone5添加183。这两个值是我通过反复试验得出的。如果我不添加这些，则 textView 会延伸到键盘下方。请帮我解开这个谜团。

In viewWillAppear方法，添加以下内容：

- (void) viewWillAppear:(BOOL)paramAnimated{
    [super viewWillAppear:paramAnimated];

    [[NSNotificationCenter defaultCenter] 
        addObserver:self 
           selector:@selector(handleKeyboardDidShow:) 
               name:UIKeyboardDidShowNotification object:nil];

    [[NSNotificationCenter defaultCenter]
        addObserver:self
           selector:@selector(handleKeyboardWillHide:)     
               name:UIKeyboardWillHideNotification object:nil];    
}

然后实现通知中心的两个方法，如下：

- (void) handleKeyboardDidShow:(NSNotification *)paramNotification{

    NSValue *keyboardRectAsObject =
        [[paramNotification userInfo] 
            objectForKey:UIKeyboardFrameEndUserInfoKey];

    CGRect keyboardRect = CGRectZero;
    [keyboardRectAsObject getValue:&keyboardRect];

    yourTextView.contentInset =
        UIEdgeInsetsMake(0.0f,
                         0.0f,
                         keyboardRect.size.height,
                         0.0f);
}

另一种是这样的：

- (void) handleKeyboardWillHide:(NSNotification *)paramNotification{

    yourTextView.contentInset = UIEdgeInsetsZero;
}

它将适用于所有设备；）