title: Use WKWebView to display link pdf cause invisible keyboard view
body: <p>I try to use WKWebView to display a link pdf, it works, but when I check the view hierarchy, I found this cause an invisible keyboard window, and an auto layout issue. because this a system issue, I do not know how to fix it.
  this is my code:</p>
  <pre><code>self.webView = [[WKWebView alloc]initWithFrame:self.view.bounds configuration:configuration];
  _webView.backgroundColor = [UIColor clearColor];
  _webView.allowsBackForwardNavigationGestures =YES;
  _webView.scrollView.decelerationRate = UIScrollViewDecelerationRateNormal;
  
  [self.view addSubview:self.webView];
  
  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[@&quot;https://xxxxxxx.pdf&quot; stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]]]];
  [_webView loadRequest:request];
  </code></pre>
  <p>this is the Debug view Hierarchy:
  <a href="https://i.stack.imgur.com/sz8w4.png" rel="nofollow noreferrer">enter image description here</a></p>
  <p>this is the auto layout issue:
  <a href="https://i.stack.imgur.com/kKHMb.png" rel="nofollow noreferrer">enter image description here</a></p>