title: I use the UIView `animateWithDuration:animations:` method to animate my view, it's bottom constant change, but it shows did not animate
body: <p>I use the UIView <code>animateWithDuration:animations:</code> method to animate my view, it's bottom constant change, but it shows did not animate.</p>
  
  <p>My code is below:</p>
  
  <pre><code>@property (weak, nonatomic) IBOutlet NSLayoutConstraint *bottom_tableView;
  
  ...
  // my animate method
  - (void)hideSelf {
      [UIView animateWithDuration:0.5 animations:^{
  
          _upspringBackView.alpha = 0.f;
          _bottom_tableView.constant = -_tableView.bounds.size.height - 49;
      } completion:^(BOOL finished) {
  
          if (finished) {
  
              self.hidden = YES;
          }
      }];
  }
  </code></pre>
  
  <p>I don't know why, my code is no problem.</p>